1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. TITLE OF THE INVENTION: –: “INDUSTRIAL IMPROVED PROCESS FOR
PREPARATION OF CIS CEVIMELINE HYDROCHLORIDE”

2. APPLICANT:
a) NAME : Kalintis Healthcare Private limited
b) NATIONALITY : Indian.
c) ADDRESS : No.52A, Jarod Samlaya Road Garadhia PO, Taluka
Savli,Vododara, Gujarat, India-391520
(a)
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which
it is to be performed.
2
Industrial Improved Process for Preparation of Cis Cevimeline Hydrochloride
Field of the Invention
5 The invention relates to an economical, eco-friendly, and industrially viable process
of preparing high-quality product cis-2-methylspiro(1,3-oxathiolane-5,3')
quinuclidine hydrochloride commonly known as Cis Cevimeline Hydrochloride.
High quality product implies a product having purity of at least 98 %, preferably at
least 99 %, and more preferably at least 99.50 % of the Cis isomer. High quality
10 also implies not detectable or minute acceptable levels of other impurities. Finally,
high-quality product also implies that Cis Cevimeline Hydrochloride of the desired
particle size is produced.
Objects of the Invention
15 First object of the present invention is to provide an economical, eco-friendly and
industrially viable process of preparing high-quality product cis-2-methylspiro(1,3-
oxathiolane-5,3') quinuclidine hydrochloride commonly known as Cis Cevimeline
Hydrochloride.
Under this object, inventors have carefully chosen process conditions to arrive at
20 Cis Cevimeline Hydrochloride through a process that provides better yields and
wherein process employs simple, safe and easily available reactants.
The second object of the present invention is to provide a process of preparing pure
cis-2-methylspiro(1,3-oxathiolane-5,3') quinuclidine hydrochloride commonly
known as Cis Cevimeline Hydrochloride wherein cis isomer so produced is at least
25 98 %, preferably at least 99 % and more preferably, at least 99.50 % pure. Highly
pure Cis Cevimeline Hydrochloride is obtained by controlling processes and purity
of all intermediates.
The third object of the present invention is to provide a process of preparing pure
cis-2-methylspiro(1,3-oxathiolane-5,3') quinuclidine hydrochloride commonly
30 known as Cis Cevimeline Hydrochloride wherein cis isomer so produced contains
3
no detectable levels or acceptable levels of all other impurities including two newly
identified acid degradation impurities.
The fourth object of the present invention is to provide a process of preparing pure
cis-2-methylspiro(1,3-oxathiolane-5,3') quinuclidine hydrochloride commonly
5 known as Cis Cevimeline Hydrochloride wherein the particle size of the cis isomer
so produced is desirable, consistent and reproducible.
Background of the Invention
US Patent: 4,855,290 and CA 1311479C, Fisher et al.
10 US pat. No. 4,855,290/CA l311479C describes process for 3-Hydroxy-3-
mercaptomethylene quinuclidine using, trimethyl sulfonium iodide, sodium
hydride in DMSO form dimethylsulfoxonium methylide. It is further reacted with
3-Quinuclidinone in DMSO to form epoxide of 3-methylene quinuclidine. Then
reacted with H2S gas in presence of aqueous NaOH in MDC and methanol as
15 solvent produced thiol compound as insitu intermediate. It is insitu reacted with
boron trifluoride etherate and acetaldehyde to form racemic cevimeline base, on
treatment with dry HCl gas in chlorofom1 produce racemic Cevimeline
hydrochloride which on fractional crystallization with ethyl acetate then several
times with acetone produce Cis cevimeline hydrochloride with around 33-40%
20 overall yield.
The drawback of this process was that it provided a low yield of the intermediate
due to the formation of the side product, Diol, from the epoxide in-situ intermediate
in the presence of a sodium hydroxide solution and the recommended temperature
conditions. It also required continuous hydrogen sulfide gas. By passing hydrogen
25 sulfide gas continuously for more than 6.0 hrs., the amount of hydrogen sulfide gas
was very high, requiring 6.50 kg of hydrogen sulfide gas for a 13. 9 gm batch size.
This poses a significant environmental concern. Hydrogen sulfide is also toxic in
nature. Handling it at a commercial scale is difficult due to safety concerns.
4
Additionally, this process lacks scalability due to multiple recrystallization steps
and chromatographic purification needed to enrich the cis isomer. This process was
not suitable for commercialization.
USPat.No.5571918/US4861886 describes A method for condensing 3-hydroxy-3-
5 mercapto methyl quinuclidine with acetaldehyde in presence of organic sulfonic
acid, anhydride and tin halide, or oxy acid of phosphorous producing 2-
methylspiro(l,3-oxathiolane-5,3') quinuclidine, which comprises isomerizing transform of 2-methylspiro(l ,3-oxathiolane-5 ,3 ') quinuclidine or acid addition salts
thereof in the presence of a catalyst tin halide, to produce cis-form 2methylspiro
10 (l,3-oxathiolane-5,3') quinuclidine or its salt. Product extraction in n-hexane after
basic and acid treatment followed by hydrochlorination with HCl gas produced Cis
Cevimeline hydrochloride.
The drawback of this process is that the key starting material, 3-hydroxy-3-
mercptomethyl quinuclidine, is not stable. Additionally, hazardous materials like
15 p-toluene sulfonic acid and oxy acids of phosphorus are used for the condensation
reaction with acetaldehyde.
No method has been described for the complete conversion of trans isomers to cis
isomers by the conventional process mentioned for the preparation of cis
Cevimeline hydrochloride.
20 US pat No.4981858 and EP0303391 describe the resolution of 2-methylspiro (l ,3-
oxathiolane5,3') quinuclidine with L-tartaric acid or D- tartaric acid to form tartrate
salt, further treatment with aqueous sodium hydroxide in water followed by
extraction with n-hexane and hydrochlorination with alcoholic HCl produce Cis
Cevimeline hydrochloride.
25 The drawback of this process is that the yield is very low (26%), and there was no
further discussion on the purification of tartrate salt of cis 2-methylspiro (l ,3-
oxathiolane-5,3') quinuclidine to get desired cis isomers. Therefore, this process
was not economically viable.
US20130060036 / WO2011049155 describes a production method for a cis-type 2-
30 alkylspiro( 1,3-oxathiolane-5,3 ') quinuclidine hydrochloride, comprising: reacting
5
a cis-trans isomer mixture of 2-alkylspiro(l,3-oxathiolane-5,3') quinuclidine
(racemic mixture) with p-nitrobenzoic acid; resolving the resultant product to
produce a cis-type 2-alkylspiro (l,3 -oxathiolane-5,3 ') quinuclidine p-nitrobenzoate
followed by multiple purification in water to obtained pure p-nitrobenzoate salt.
5 and converting the p-nitrobenzoate into a hydrochloride salt using hydrocarbon
solvent such as toluene, hexane, heptane with IPA.HCl produces Cis Cevimeline
Hydrochloride.
The above process produces a p-nitrobenzoate salt of racemic Cevimeline and such
racemic salt is further resolved into Cis Cevimeline p-nitro benzoate salt. In this
10 process, around 35-40% of the trans isomer of Cis Cevimeline p-nitrobenzoate was
lost in the mother liquor. To recover this isomer, further isomerization with boron
trifluoride ether complex with hydrobromic acid and aldehyde was required, which
reduced the overall yield of the Cis isomer.
US Pat.Nos. US8080663/US 2008249312/US8143400/US20090182146 describe
15 Resolution of racemic cevimeline base with racemic camphor sulfonic acid in
toluene to produce cis cevimeline camphor sulfonic acid salt (95:5).
Recrystallization in toluene and methanol (or alternate solvent mixture) produce
Cis cevimeline camphor sulfonic acid salt as cis isomer. This salt was further
treated with aqueous sodium carbonate in water followed by extraction with
20 heptane, solvent recovery and crystallization in diethyl ether/DIPE by adding
IPA.HCl produces Cis Cevimeline hydrochloride.
None of the prior art provides the impurity profile of the final compound Cis
Cevimeline Hydrochloride and is silent about several specified impurities such as
diol, thiol, sulfoxide (RRR and RRS), N-oxide etc. The prior arts are also silent
25 about % of trans isomer. There is no mention of stability testing and results of such
testing at accelerated and / or long term stability conditions.
6
Summary of the Invention
Under the first aspect, the invention provides an economical, eco-friendly and
industrially viable process of preparing high-quality product cis-2-methylspiro(1,3-
oxathiolane-5,3') quinuclidine hydrochloride commonly known as Cis Cevimeline
5 Hydrochloride.
The process comprises four stages, each providing a pure intermediate/final
product.
High-quality product implies a product having a purity of at least 98 %, preferably
at least 99 %, and more preferably at least 99.50 % of the Cis isomer. High quality
10 also implies not detectable or minute acceptable levels of other impurities. Finally,
a high-quality product also implies that Cis Cevimeline Hydrochloride of the
desired particle size is produced.
Under another aspect, the invention provides two acid degradants/impurities 1 and
2 newly found and produced due to an acid degradation of Cevimeline. These two
15 impurities are named as 1 and 2 and are
a) Cevimeline impurity-1: 3-(((1-((((1R,4R)-3-Hydroxyquinuclidin-3-yl) methyl)
thio) ethyl) thio) methyl) quinuclidin-3-ol; and
b) Cevimeline impurity-2: 3-(((1-((((1S,4S)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.
20 Under yet another aspect, the invention provides Cis Cevimeline Hydrochloride
containing not more than 0.15 % of a single specified impurity selected from
i) Cevimeline impurity-1: 3-(((1-((((1R,4R)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol; and
ii) Cevimeline impurity-2: 3-(((1-((((1S,4S)-3-Hydroxyquinuclidin-3-yl)
25 methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.
Under a couple of aspects, Cis Cevimeline Hydrochloride of desired particle size is
produced.
One more aspect of the invention provides Cis cevimeline hydrochloride with the
following particle size distribution,
30 D10: not more than 5µm;
D50: not more than 10µm;
7
D90: not more than 25 µm, preferably not more than 20 µm, most preferably not
more than 15 µm;
wherein Cis cevimeline hydrochloride is slurried in isopropyl alcohol and dried
before particle size measurement.
5 One more aspect of the invention provides Cis cevimeline hydrochloride with the
following particle size distribution,
D10: not more than 20µm, preferably not more than 10 µm and more preferably not
more than 7.5 µm;
D50: not more than 50µm; preferably not more than 30 µm and more preferably
10 between 10 µm - 25 µm;
D90: not more than 100 µm, preferably not more than 80 µm, most preferably not
more than 75 µm.
wherein Cis cevimeline hydrochloride is dissolved in isopropyl alcohol and
precipitated by cyclohexane and dried before particle size measurement.
15
Brief description of drawings
Figure 1 provides a chromatogram of the CVM-I intermediate resulting from stage
-I of the process provided under example 1.
Figure 2 provides a chromatogram of CVM-II intermediate resulting from stage -II
20 of the process provided under example 2.
Figure 3 provides a chromatogram of CVM-III intermediate resulting from stageIII of the process provided under example 3. The CVM-III intermediate is Cis
Cevimeline para nitro benzoic acid salt. The peak eluted at RT 10 is of p-nitro
benzoic acid of this salt.
25 Figure 4 provides Cis Cevimeline Hydrochloride prepared in accordance with the
present invention having 0.04 % of a trans isomer. Cis Cevimeline Hydrochloride
purity is 99.96 %.
Figure 5 provides Cis Cevimeline Hydrochloride prepared in accordance with the
present invention having below detectable levels of any impurity. Cis Cevimeline
30 Hydrochloride purity is 99.97 %.
8
Figures 6A and 6B provide particle size distribution data of Cis Cevimeline
Hydrochloride prepared using a solvent treatment wherein Cis Cevimeline
Hydrochloride is dissolved in isopropyl alcohol and precipitated by cyclohexane.
Figures 7A and 7B provide particle size distribution data of Cis Cevimeline
5 Hydrochloride prepared using a solvent treatment wherein Cis Cevimeline
Hydrochloride is subject to slurry in isopropyl alcohol.
Figure 8 provides IR spectra of Cis Cevimeline p-nitro benzoic acid salt.
Figure 9 provides the Mass spectra of Cis Cevimeline p-nitro benzoic acid salt.
Figure 10A provides 1H NMR (proton NMR) spectra of Cis Cevimeline p-nitro
10 benzoic acid salt.
Figure 10B provides 1H NMR (proton NMR) spectra of Cis Cevimeline p-nitro
benzoic acid salt enlarged in the 1.2 ppm – 3.6 ppm region.
Figure 10C provides 1H NMR (proton NMR) spectra of Cis Cevimeline p-nitro
benzoic acid salt enlarged in the 5 ppm – 9.5 ppm region.
15 Figure 11 A provides 13C NMR spectra of Cis Cevimeline p-nitro benzoic acid salt.
Figure 11 B provides 13C NMR spectra of Cis Cevimeline p-nitro benzoic acid salt
enlarged in the region of 15 ppm –90ppm.
Figure 11 C provides 13C NMR spectra of Cis Cevimeline p-nitro benzoic acid salt
enlarged in the region of 120 ppm – 175ppm.
20 Figures 12A and 12B provide HPLC chromatograms of CVM-III by method 1 and
method 2 respectively, wherein CVM-III is not prepared in accordance with the
present invention.
Figures 13A and 13B provide HPLC chromatograms of Cis Cevimeline
Hydrochloride by method 1 and method 2 respectively, wherein Cis Cevimeline
25 Hydrochloride is not prepared in accordance with the present invention.
Figures 14A and 14B provide 1H NMR (proton NMR) spectra of a mixture of CVM
impurity 1 and 2 wherein such mixture is at least 90 % pure. Figure 14B provides
9
1H NMR (proton NMR) spectra of said impurity mixture enlarged in the 1 ppm –
6 ppm region.
Figure 14C provides 13C NMR spectra of a mixture of CVM impurity 1 and 2
wherein such mixture is at least 90 % pure.
5 Figure 14D provides 13C NMR spectra of a mixture of CVM impurity 1 and 2
enlarged in the region of 10 ppm – 180 ppm.
Figure 15 provides the Mass spectra of of a mixture of CVM impurity 1 and 2
wherein such mixture is at least 90 % pure.
Figures 16A and 16B provide IR spectra of a mixture of CVM impurity 1 and 2
10 wherein such mixture is at least 90 % pure and IR peak details including peak
intensity, height, and area.
Figures 17A and 17B, figures 18A and 18B, and figures 19A and 19B provide 3 test
results of testing the purity of a mixture of CVM impurity 1 and 2 by HPLC
providing that the purity of a mixture of CVM impurity 1 and 2 is always at least
15 90 %.
10
Detailed description of the invention
The present invention discloses an economical, eco-friendly and industrially viable
process of preparing high-quality product cis-2-methylspiro(1,3-oxathiolane-5,3')
quinuclidine hydrochloride commonly known as Cis Cevimeline Hydrochloride.
5 More particularly, the present invention discloses a process that leads to a highquality product in terms of isomer purity, chemical purity, and particle size.
The process of preparing High-quality Cis Cevimeline Hydrochloride of the present
invention proceeds through 4 stages as follows,
1. Stage-I: Preparation of Thioacetic Acid Salt of 3-hydroxy-3-
10 acetoxymercapto methyl quinuclidine (CVM-I) from 3-Quinuclidinone
hydrochloride through in situ formation of Epoxide of 3-methyelene quinuclidine;
2. Stage-II: Preparation of Racemic Cevimeline Hydrochloride Hemihydrate
(CVM-II) from Thioacetic Acid Salt of 3-hydroxy-3-acetoxymercapto methyl
quinuclidine (CVM-I);
15 3. Stage-III: Preparation of Cis Cevimeline organic acid salt preferably, para
nitro benzoic acid salt (CVM-III) from Racemic Cevimeline Hydrochloride
Hemihydrate (CVM-II) through in situ formation of Cis Cevimeline base; and
4. Stage-IV: Preparation of Cis Cevimeline Hydrochloride (A-012) from Cis
Cevimeline organic acid salt.
20
More particularly, the process of preparing High-quality Cis Cevimeline
Hydrochloride of the present invention involves
i) Preparation of Cis Cevimeline organic acid salt preferably, para nitro
benzoic acid salt (CVM-III) from Racemic Cevimeline Hydrochloride
25 Hemihydrate (CVM-II) through in situ formation of Cis Cevimeline base;
and
ii) Preparation of Cis Cevimeline Hydrochloride (A-012) from Cis Cevimeline
organic acid salt.
More particularly, optimized process conditions are chosen in each step coupled
30 with purification of intermediates wherever necessary, to arrive at Cis Cevimeline
11
Hydrochloride through a process which provides better yields and quality at each
of the stages I to IV.
The inventors of the present invention have surprisingly observed that a process to
produce Cis Cevimeline Hydrochloride greatly impacts its purity and impurity
5 profile along with levels of impurities. The purity of the final product is very
sensitive to various conditions employed during synthesis. The use of solvent,
amount of solvent, reactants, and temperature conditions greatly impact the purity
of intermediates as well as Cis Cevimeline Hydrochloride.
Particularly, Trans isomer has to be restricted in the synthesis. United States
10 pharmacopeial limit for the trans isomer in Cis Cevimeline Hydrochloride is only
0.5 %. It has been far more difficult to restrict trans isomer below 0.5 % and further,
it is essential to ensure that it does not increase when subjected to various long-term
and accelerated stability conditions.
Most of the prior arts are silent about the impurity profile of Cis Cevimeline
15 Hydrochloride and various intermediates of Cis Cevimeline Hydrochloride.
Cis Cevimeline Hydrochloride, apart from trans isomer may contain other
impurities such as
i) Diol impurity;
ii) Thiol impurity
20 iii) Cevimeline Sulfoxide (RRS )impurity;
iv) Cevimeline Sulfoxide (RRR )impurity;
v) Cevimeline -N-oxide;
vi) Any additional impurity based on the process developed.
The invention provides Cis Cevimeline Hydrochloride containing
25 i) not more than 0.5 %, preferably not more than 0.3 % of Trans isomer;
ii) Not more than 0.1 % of single unspecified impurity;
iii) Not more than 0.15 % of single specified impurity selected from
a) Cevimeline sulfoxide (RRR);
b) Cevimeline sulfoxide (RRS);
12
c) Cevimeline N-Oxide;
d) Cevimeline impurity-1: 3-(((1-((((1R,4R)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol; and
e) Cevimeline impurity-2: 3-(((1-((((1S,4S)-3-Hydroxyquinuclidin-3-yl)
5 methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.
iv) Not more than 0.1 % of diol impurity;
v) Not more than 0.1 % of thiol impurity.
Most of the prior arts fail to provide chromatograms of Cis Cevimeline and its
10 intermediates; and are largely silent about controlling various impurities.
It is also difficult for a single method to detect all impurities. It is observed that a
method employed and known for estimating trans impurity in Cis Cevimeline
Hydrochloride, hereinafter method I or Method 1, fails to resolve and estimate all
other impurities. It was hence needed to develop one or more further methods for
15 the estimation of other impurities. Accordingly, a second method hereinafter
Method II or Method 2 has been developed to ensure that all probable impurities
are resolved and can be estimated. A system suitability test ensured the resolution
and estimation of other impurities.
With method II, two newly observed impurities as follows are found in the samples
20 of Cis Cevimeline Hydrochloride,
i) Cevimeline impurity-1: 3-(((1-((((1r,4r)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.; and
ii) Cevimeline impurity-2 : 3-(((1-((((1s,4s)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.
25 Thus, under another aspect the invention provides,
i) Cevimeline impurity-1: 3-(((1-((((1r,4r)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.; and
ii) Cevimeline impurity-2 : 3-(((1-((((1s,4s)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.
30
13
Under further aspect, the invention provides Cis Cevimeline Hydrochloride
containing not more than 0.15 % of a single specified impurity selected from
i) Cevimeline impurity-1: 3-(((1-((((1R,4R)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol; and
5 ii) Cevimeline impurity-2: 3-(((1-((((1S,4S)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.
With these two newly found impurities, the task of developing a suitable process
that can control impurities became more challenging. The present invention
discloses a novel process to prepare high-quality Cis Cevimeline Hydrochloride.
10 The process successfully produced highly pure Cis Cevimeline Hydrochloride with
controlled impurities.
Further, during the development of the process, inventors serendipitously arrived at
a process modification to provide Cis Cevimeline Hydrochloride with a controlled
particle size. This particle size ensures uniform particles and better processibility
15 of Cis Cevimeline Hydrochloride.
Under an aspect, the invention provides Cis cevimeline hydrochloride with the
following particle size distribution,
D10: not more than 5µm;
D50: not more than 10µm;
20 D90: not more than 25 µm, preferably not more than 20 µm, most preferably not
more than 15 µm;
wherein Cis cevimeline hydrochloride is slurried in isopropyl alcohol and dried
before particle size measurement.
Figures 7A and 7B provide particle size distribution data of Cis Cevimeline
25 Hydrochloride prepared using a solvent treatment wherein Cis Cevimeline
Hydrochloride is subject to slurry in isopropyl alcohol.
Under one more aspect, the invention provides Cis cevimeline hydrochloride with
the following particle size distribution,
14
D10: not more than 20µm, preferably not more than 10 µm and more preferably not
more than 7.5 µm;
D50: not more than 50µm; preferably not more than 30 µm and more preferably
between 10 µm - 25 µm;
5 D90: not more than 100 µm, preferably not more than 80 µm, most preferably not
more than 75 µm;
wherein Cis cevimeline hydrochloride is dissolved in isopropyl alcohol and
precipitated by cyclohexane and dried before particle size measurement.
Figures 6A and 6B provide particle size distribution data of Cis Cevimeline
10 Hydrochloride prepared using a solvent treatment wherein Cis Cevimeline
Hydrochloride is dissolved in isopropyl alcohol and precipitated by cyclohexane.
The development of a process that can produce Cis Cevimeline Hydrochloride of
high purity with controlled impurities was challenging, and Inventors stumbled
15 upon several unsuccessful experiments before arriving at successful ones as small
changes in experiments impacted the purity of products in each reaction requiring
consideration of several permutations.
The inventors conducted a series of experiments followed by optimization at
various levels to arrive at Cis Cevimeline Hydrochloride having a purity of at least
20 98 %, preferably at least 99 %, and more preferably at least 99.50 %.
The optimum process conditions are achieved by choosing the right process
conditions from several alternatives of solvent, reactants, molar ratios, temperatures
of reaction, purification processes etc.
Isomerizing racemic cevimeline hydrochloride (65:35 Cis and Trans ratio) is tried
25 using a metal catalyst (such as stannic chloride) wherein racemic cevimeline
hydrochloride is converted into Cis cevimeline base. Such base nevertheless
contains around 5.0 % trans isomer. Such high levels are not acceptable. Hence
further processing is essential to limit the trans isomer.
15
Cis Cevimeline base having up to 5 % trans isomer is reacted with DL camphor
sulfonic acid to form Cis Cevimeline camphor sulfonic acid salt. Surprisingly this
escalated instead of reducing impurities and total impurities are found to be 19.71
% including trans isomer of 2.53 %.
5 The following table 1 provides a compilation of impurities generated in the reaction
and the corresponding chromatogram is provided in Figure 12A.
Table 1
Tests Specifications
HPLC results
CRD/A-012-
PBP/
016/161-C
Organic impurities by HPLC <621> (by % area)
Method I by HPLC
Trans Cevimeline impurity Not more than 0.30 % 2.53%
Method II by HPLC
Diol impurity Not more than 0.15 % 0.01%
Thiol impurity Not more than 0.15 % Not detected
Cevimeline sulfoxide (RRS) Not more than 0.15 % 0.25%
Cevimeline sulfoxide (RRR) Not more than 0.15 % 0.19%
Cevimeline N-Oxide Not more than 0.15 % 0.03%
Cevimeline impurity-1: 3-(((1-
((((1r,4r)-3 Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl)
quinuclidin-3-ol.
Not more than 0.15 %
0.14%
Cevimeline impurity-2: 3-(((1-
((((1s,4s)-3-Hydroxyquinuclidin-3-
yl) methyl) thio) ethyl) thio) methyl)
quinuclidin-3-ol.
Not more than 0.15 %
0.02%
Single largest unspecified impurity
Not more than 0.15 %
8.23%, 0.15%,
1.51%, 1.02%,
0.61%, 0.18%,
0.15%, 1.17%,
1.51%, 0.20%,
0.16%, 0.23%,
0.19%,
0.16%
Total Impurities (Total impurities of
Method-II +Trans isomer in MethodI)
Not more than 1.50 %
19.71%
16
The further reactions employed p-nitro benzoic acid instead of DL camphor sulfonic
acid to produce Cis Cevimeline para nitrobenzoic acid salt.
Cis cevimeline para nitrobenzoic acid salt is reacted with sodium hydroxide
solution followed by pH adjustment to above 11.5. This was followed by extraction
5 using diisopropyl ether. The diisopropyl ether extract was treated with isopropyl
alcohol hydrochloride (IPA.HCl) to produce Cis Cevimeline hydrochloride.
This process to produce Cis Cevimeline Hydrochloride generated several specified
and un specified impurities as mentioned in table 2 below.
This batch fails to comply miserably with the requirements as per ICH guidelines.
10 The corresponding chromatogram is provided in Fig. 13A.
Table 2
HPLC results:
Tests HPLC results
Organic impurities by HPLC <621>
Trans Cevimeline impurity 0.81%
Diol impurity Not detected
Thiol impurity Not detected
Cevimeline sulfoxide (RRR) 0.16%
Cevimeline sulfoxide (RRS) 0.20%
Cevimeline N-Oxide Not detected
Cevimeline impurity-1: 3-(((1-((((1r,4r)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl)
thio) methyl) quinuclidin-3-ol.
Not detected
Cevimeline impurity-2 : 3-(((1-((((1s,4s)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl)
thio) methyl) quinuclidin-3-ol.
Not detected
Single largest unspecified impurity 0.11%, 0.26%
Total impurities
(Total impurity of Method II + Trans isomer) 1.82%
17
Surprisingly it is found that the generation of impurities in the above reaction was
due to the use of Diisopropyl ether for extraction and further reactions. Replacing
diisopropyl ether with other solvents was found useful. Hence use of Diisopropyl
ether for extraction and further reactions is not part of the present invention.
5 Through several failed experiments, it was clear that small changes in the reaction
conditions had a significant impact on the purity of the product at each stage as well
as on the overall impurity profile.
In the past, racemic cevimeline hydrochloride had been employed to prepare Cis
Cevimeline Hydrochloride (US Patent: 4,855,290 and CA 1311479C, Fisher et al.);
10 however, this reaction had several drawbacks. First, it resulted in a very low yield
and also generated Diol impurity.
In past, various acids have been employed in producing Cis Cevimeline
Hydrochloride including L-tartaric acid or D-tartaric acid (US Pat.No.4981858/
EP0303391), Camphor sulfonic acid (US8080663/US
15 2008249312/US8143400/US20090182146), p-Nitro benzoic acid
(US20130060036 WO2011049155) etc. But in none of these reactions, Cis
Cevimeline Hydrochloride has been prepared from Cis Cevimeline base.
It was never thought to isomerize Racemic Cevimeline Hydrochloride to Cis
Cevimeline base and to further process it into Cis Cevimeline Hydrochloride.
20 Inventors have tried following organic and inorganic acids as provided in table 3
below to prepare the corresponding salt. But no acid was found as good as p-nitro
benzoic acid.
Table 3
Sr. No. Acid Salt Purity and Impurities
1. Conc.
H2SO4
Cis Cevimeline
sulfate salt
Cis isomer = 95.72 %; trans isomer
4.28 %;
CVM-1 0.27 %, CVM-2 in 0.28 %
18
2. Methane
sulfonic
acid
Cis Cevimeline
methane sulfonic
acid
Cis isomer = 96.93 %; trans isomer
3.07 %;
CVM-1 0.10 %, CVM-2 in 0.17 %
3. DLcamphor
sulfonic
acid
Cis Cevimeline
camphor sulfonic
acid salt
Cis isomer = 97.47 %; trans isomer
2.53 %;
CVM-1 0.14 %, CVM-2 in 0.02 %;
CVM RRR – 0.19 %;
CVM RRS – 0.25 %;
4. p-nitro
benzoic
acid
Cis Cevimeline pnitro benzoic acid
salt
Cis isomer = 99.86 %; trans isomer
0.14 %;
No other impurities observed.
5. ptoluene
sulfonic
acid
Product could not be isolated
Pursuant to selection of p-nitro benzoic acid for preparing Cis Cevimeline
Hydrochloride p-nitro benzoic acid salt, few other impurities are also checked and
controlled as per ICH M7 guideline.
5 Additional controlled impurities by HPLC include
i) 2-Nitro Benzoic Acid
ii) 2,4 Dinitro Benzoic Acid
iii) 4-Nitro Benzoic Acid
iv) 3-Nitro Benzoic Acid
10 v) 3,4 Dinitro Benzoic Acid
vi) 4-Niro Toluene.
Even when the inventors tried isomerizing racemic Cevimeline Hydrochloride salt
(65:35 cis-trans ratio) to Cis Cevimeline base, it contained up to 5.0% trans isomer
which was not acceptable. Further Cis Cevimeline base having up to 5 % trans
15 isomer is reacted with DL camphor sulfonic acid to form Cis Cevimeline camphor
19
sulfonic acid salt. Surprisingly this escalated instead of reducing impurities and
total impurities are found to be 19.71 % including trans isomer of 2.53 %.
Therefore, it was much needed to find a solution to arrive at pure Cis Cevimeline
Hydrochloride using alternative processes.
5 The process of the present invention involves isomerizing racemic cevimeline
hydrochloride salt (65:35 cis trans ratio) using Lewis acid metal catalyst to Cis
cevimeline base prepared in situ containing up to 5.0% trans isomer and reacting
Cis-Cevimeline base (instead of racemic Cevimeline Hydrochloride) prepared in
situ with an organic acid to produce an organic acid salt of Cis-Cevimeline. The
10 said organic acid is inexpensive and easily and abundantly available commercially.
The process further provides preparing Cis-Cevimeline Hydrochloride from CisCevimeline organic acid salt.
More particularly, the present invention provides a process to prepare Cis
Cevimeline Hydrochloride hemihydrate through formation of an intermediate Cis15 Cevimeline organic acid salt, preferably an intermediate Cis-Cevimeline para nitro
benzoic acid salt- (CVM-III) by reacting Cis cevimeline base (having 5.0% trans
isomer) prepared in situ with p-nitro benzoic acid. The cis cevimeline base is
prepared from racemic Cevimeline hydrochloride hemihydrate (CVM-II).
The present invention also provides preparation of Racemic Cevimeline
20 Hydrochloride Hemihydrate (CVM-II) from thioacetic acid salt of 3-hydroxy-3-
acetoxymercapto methyl quinuclidine. The thioacetic acid salt is produced under
Stage I by a two-step process wherein in the first step epoxide of 3-methylene
quinuclidine is produced in situ which is subsequently reacted with Thioacetic acid
to produce thioacetic acid salt of 3-hydroxy-3-acetoxymercapto methyl
25 quinuclidine.
This thioacetic acid salt of 3-hydroxy-3-acetoxymercapto methyl quinuclidine is
reacted with IPA.HCl and Acetaldehyde diethyl acetal to produce Racemic
Cevimeline hydrochloride (65:35).
20
Conversion of racemic cevimeline hydrochloride salt (65:35 cis trans ratio) using
Lewis acid metal catalyst with inorganic acid (IPA.HCl) to Cis cevimeline base
containing not more than 5 % trans isomer, more particularly, from 0.5-5.0 % trans
isomer is extremely crucial before reacting with an organic acid to produce Cis5 Cevimeline organic acid salt. Instead, if racemic cevimeline base without
isomerization with Lewis acid metal catalyst is directly reacted with an organic
acid, it results in loss of trans isomer from 35 – 40 % in mother liquor which can
reduce yield by 35 % or more.
The said process of isomerizing racemic Cevimeline hydrochloride enhances
10 chemical purity of Cis Cevimeline hydrochloride as well as keeps in control several
other impurities. .
Racemic Cevimeline hydrochloride hemihydrate is reacted with Lewis acid / metal
catalyst more particularly, stannic chloride and isopropyl alcohol hydrochloride in
a dichloromethane solvent. The reaction is then quenched with water and the
15 mixture is basified using a sodium hydroxide solution.
Dichloromethane layer is separated and treated with an aqueous sulfuric acid
solution; the pH of the aqueous layer is adjusted to a basic pH using sodium
hydroxide solution. Cis Cevimeline base formed is extracted with toluene and
obtained after solvent recovery.
20 Further, Cis Cevimeline base is reacted with p-nitrobenzoic acid leading to the
formation of Crude Cis Cevimeline para nitrobenzoic acid salt in acetone. This
crude salt is then purified in purified water, yielding the final product, Cis
Cevimeline para nitrobenzoic acid salt.
25 In the final step, Cis Cevimeline para nitrobenzoic acid salt is first basified using a
Sodium hydroxide solution in purified water. The basified product is then extracted
with Cyclohexane, leading to separation of layers.
The organic layers are subjected to a carbon treatment followed by filtration. The
filtrate is treated with dilute isopropyl alcohol hydrochloride to adjust the pH to
30 acidic levels, resulting in the formation of Cis-Cevimeline Hydrochloride.
21
This Cis-Cevimeline Hydrochloride is further refined through a solvent treatment
which comprises slurring in a solvent or recrystallization using a pair of solvent and
anti-solvent. The recrystallization process uses a mixture of polar and non-polar
solvents such asisopropyl alcohol as solvent for dissolving and cyclohexane as anti5 solvent for precipitating.
The result of this final step is the production of the Active Pharmaceutical
Ingredient (API), Cis-Cevimeline Hydrochloride having following characteristics
i. Cis-Cevimeline Hydrochloride with cis isomer is at least 99 %, preferably
10 at least 99.5 % and more preferably, at least 99.7 % restricting trans isomer to not
more than 1 %, preferably not more than 0.5 % and more preferably, not more than
0.3 %.
ii. Cis-Cevimeline Hydrochloride of high chemical purity having any single
largest unspecified impurity not more than 0.1 %
15 iii. particle size as below,
D10: Not more than 20 µm , preferably not more than 10 µm, more preferably not
more than 7.5 µm, most preferably Between 1.0 and 7.5 µm
D50: Not more than 50 µm, preferably not more than 30 µm, more preferably not
more than 25 µm, most preferably Between 10.0 and 25.0 µm
20 D90: Not more than 100 µm, preferably not more than 80 µm, more preferably not
more than 75 µm, most preferably Between 30.0 and 75.0 µm.
Or
particle size as below,
D10: Not more than 5 µm,
25 D50: Not more than 10 µm,
D90: Not more than 25 µm, preferably not more than 20 µm, more preferably not
more than 15 µm.
Depending on the solvent treatment chosen.
30 iv. Further, in such pure Cis-Cevimeline Hydrochloride, two new acid
degradation impurities namely 3-(((1-((((1s,4s)-3-Hydroxyquinuclidin-3-yl)
22
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol (Cevimeline impurity-1) and 3-
(((1-((((1r,4r)-3-Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl)
quinuclidin-3-ol (Cevimeline impurity-2), are either not detectable or below 0.15
%.
5 v. More particularly, pure Cis-Cevimeline Hydrochloride prepared in accordance
with the present invention has following specification as provided in table 4
below:
Table 4
Tests Specifications
Organic impurities by HPLC <621>
Trans Cevimeline impurity Not more than 0.30 %
Diol impurity Not more than 0.1 %
Thiol impurity Not more than 0.1 %
Cevimeline sulfoxide (RRR) Not more than 0.15 %
Cevimeline sulfoxide (RRS) Not more than 0.15 %
Cevimeline N-Oxide Not more than 0.15 %
Cevimeline impurity-1: 3-(((1-((((1r,4r)-3- Not more than 0.15 %
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio)
methyl) quinuclidin-3-ol.
Cevimeline impurity-2: 3-(((1-((((1s,4s)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio)
methyl) quinuclidin-3-ol.
Not more than 0.15 %
Single largest unspecified impurity Not more than 0.1 %
Total impurities
(Total impurity of Method II + Trans isomer)
Not more than 1.0 %
10
Therefore, to summarize, the invention provides a process to prepare Ciscevimeline base by isomerization of racemic Cevimeline Hydrochloride
hemihydrate followed by forming an organic acid salt of Cis-cevimeline base. Cis-
23
cevimeline organic acid salt is subjected to a series of treatments such as
basification, extraction, carbon treatment, filtration and finally treated with
isopropyl alcohol hydrochloride to produce Cis-Cevimeline Hydrochloride of high
chemical purity, high isomeric purity, and desired particle size.
5 The said process also additionally provides preparation of racemic Cevimeline
Hydrochloride hemihydrate from 3-Quinuclidinone hydrochloride.
Hence, entire process can also be described as follows:
Stage-I: Preparation of Thioacetic Acid Salt of 3-hydroxy-3-acetoxymercapto
10 methyl quinuclidine (CVM-I) and optimization of process conditions.
Reaction scheme-I:
N
O
H Cl
1-azabicyclo[2.2.2]octan-3-
one hydrochloride
3-Quinuclidinone hydrochloride
+ H3C S
H3C
H3C
O
I
Trimethyl sulfoxonium iodide
Potassium
tert-butoxide
dimethylsulfoxide
Toluene
N
O
spiro[4-azabicyclo[2.2.2]octane-2,2'-oxirane]
Epoxide of 3-methyelene quinuclidine
+ H3C SH
O
Thioacetic acid
Toluene N
OH
S CH3
O
Thiolacetic Acid Salt of 3-hydroxy-3-acetoxymercaptomethyl
quinuclidine (CVM-I)
HS CH3
O
S-[(3-hydroxy-1-azabicyclo[2.2.2]oct-3-yl)methyl] ethanethioate,
thioacetic acid salt
15 Detailed process is provided under example 1.
In stage I, Thioacetic Acid Salt of 3-hydroxy-3-acetoxymercaptomethyl
quinuclidine is prepared from 3-Quinuclidinone hydrochloride in two steps.
In a first step 3-Quinuclidinone hydrochloride in a first solvent is reacted with
Trimethyl sulfoxonium iodide in presence of a base to produce in situ an
20 intermediate epoxide of 3-methylene quinuclidine. In the subsequent step, epoxide
24
of 3-methylene quinuclidine in situ is reacted with Thioacetic acid in a second
solvent environment, yielding the Thioacetic Acid Salt of 3-hydroxy-3-
acetoxymercaptomethyl quinuclidine.
It has been surprisingly noted that purity of Thioacetic Acid Salt of 3-hydroxy-3-
5 acetoxymercaptomethyl quinuclidine and its yield are impacted by several factors
such as type of first and second solvent and amount / volume of a solvent and type
of base, mole ratio of a base and the number of portions in which base is added in
the reaction, mole ratio of Trimethyl sulfoxonium iodide, mole ratio of Thioacetic
acid, reaction temperature, etc.
10
After reaction between 3-Quinuclidinone hydrochloride and trimethyl sulfoxonium
iodide to produce epoxide of 3-methylene quinuclidine in situ, the reaction is
quenched using a saturated sodium chloride solution in water.
Careful selection of a solvent and a base is necessary to obtain optimum purity and
15 yield. It has been surprisingly found that some solvents do not support the reaction
such as Isopropyl alcohol. Also, volume of a solvent is crucial. 4-5 volumes of
DMSO for reaction is sufficient to produce desired quality.
Preferably, a base is selected from sodium hydroxide, potassium hydroxide, sodium
methoxide, potassium methoxide, sodium hydride, potassium hydride, sodium
20 tertiary butoxide, potassium tertiary butoxide and any combination thereof.
Base can be added at once. But preferably, base is added in portions from 2 – 7.
Potassium tert-butoxide provided best results when added in portions from 2 – 7,
preferably in portions from 3 – 6.
For quenching with sodium chloride solution, different amounts of sodium chloride
25 were employed. Best results were obtained when 1- 1.5 % w/w of sodium chloride
is used as compared to weight of 3-Quinuclidinone hydrochloride. Once the
quantity was fixed, a 30 % solution was employed for quenching.
A first Solvent is a solvent employed in the first step where 3-Quinuclidinone
hydrochloride is reacted with Trimethyl sulfoxonium iodide to produce in situ
30 epoxide of 3-methylene quinuclidine and is selected from dimethyl sulfoxide,
25
dimethyl formamide, tetrahydrofuran and combination of dimethyl sulfoxide and
dimethyl formamide. Dimethyl sulfoxide is found to provide best yield and purity
when used in amount of from 3 – 6 volumes, preferably 4 – 5 volumes.
Second solvent is a solvent employed in the second step where epoxide of 3-
5 methylene quinuclidine prepared in situ is reacted with Thioacetic acid and is
selected from cyclohexane, Di-isopropyl ether, ethyl acetate and toluene. Best yield
and desired purity are obtained in toluene. Best mode employs toluene as a solvent.
The purity of product in all solvents is at least 90 %. Use of toluene produced > 90
%, preferably > 95 % pure Thioacetic Acid Salt of 3-hydroxy-3-
10 acetoxymercaptomethyl quinuclidine.
Even when toluene is used, optimum volume such as 15 volume or 20 volume
produced purer salt as compare to 10 volumes and 25 volumes. Thus, best mode
batch employed from 15 to 20 volumes of toluene.
To fix mole ratio of Thioacetic acid, 1 mole of epoxide of 3-methylene quinuclidine
15 prepared in situ is reacted with 1, 1.5, 2, 2.5 moles of Thioacetic acid in separate
experiments. All experiments resulted in producing Thioacetic Acid Salt of 3-
hydroxy-3-acetoxymercaptomethyl quinuclidine of at least 90 % purity wherein 1:2
mole ratio of said epoxide to Thioacetic acid provided the best results in producing
Thioacetic Acid Salt of 3-hydroxy-3-acetoxymercaptomethyl quinuclidine of at
20 least 90 %, more preferably at least 95 % purity. Thus, best mode batch employed
1:2 ratio of epoxide of 3-methylene quinuclidine and Thioacetic acid.
Further, reaction between epoxide of 3-methylene quinuclidine prepared in situ and
Thioacetic acid is carried out at various temperatures such as 0-10°C, 10-20°C, 20-
30°C and 30-40°C. It is observed that a temperature of 0-10°C is most suitable to
25 arrive at most pure Thioacetic acid salt in quantitative yields.
As temperature goes higher and higher, epoxide of 3-methylene quinuclidine is
converted into diol impurity and does not remain available to produce Thioacetic
acid salt impacting both yield and purity.
First two steps are referred as Stage-I reactions and provided under Scheme I.
30 At the end of the reaction, reaction mixture is tested for 3-Quinuclidinone
hydrochloride. It is preferred that amount of 3-Quinuclidinone hydrochloride
26
remaining unreacted is not more than 10 %, preferably not more than 5 % and more
preferably not more than 3 %.
If reaction mixture shows higher than 10 % of 3-Quinuclidinone hydrochloride, it
is stirred further and a sample is withdrawn every hour to test 3-Quinuclidinone
5 hydrochloride till it is not more than 10 %, preferably not more than 5 % and more
preferably not more than 3 %.
10 Stage II: Preparation of Racemic Cevimeline Hydrochloride Hemihydrate
(CVM-II)
Reaction scheme-II :
Thiolacetic Acid Salt of
3-hydroxy-3-acetoxymercaptome
thyl quinuclidine (CVM-I)
Isopropyl alcohol
IPA.HCL
O O
CH3
H3C CH3
Acetaldehyde diethyl acetal
Toluene
N
O
S
CH3
Aq. NaOH
Molecular Formula = C6H14O2
Formula Weight = 118.17
Molecular Formula = C10H18ClNOS 1/2.H2O
Formula Weight = 244.78
Racemic Cevimeline Hydrochloride
Hemihydrate (CVM-II)
N
OH
S CH3
O
HS CH3
O
Molecular Formula = C12H21NO3S2
Formula Weight = 291.43
Aq. H2SO4
IPA, IPA.HCl
Cyclohexane . HCL.1/2 H2O
2'-methylspiro[4-azabicyclo[2.2.2]octane-2,5
'-[1,3]oxathiolane], hydrochloride
Dichloromethane
N
OH
SH
Molecular Formula = C8H15NOS
Formula Weight = 173.28
Insitu intermediate
+
3-hydroxy-3-mercaptomethyl
quiniclidine
N
O
S
CH3
Molecular Formula = C10H17NOS
Formula Weight = 199.31
2'-methylspiro[4-azabicyclo[2.2.2]octane-2,5'-[1,3]oxathiolane]
Racemic Cevimeline Base
15
A detailed process is provided under example 2.
Under stage II, first racemic Cevimeline base is produced which is further treated
to produce Racemic Cevimeline Hydrochloride Hemihydrate.
27
The thioacetic acid salt of 3-hydroxy-3-acetoxymercapto methyl quinuclidine in a
third solvent is reacted with an acid to produce 3-hydroxy-3-mercaptomethyl
quinuclidine in situ. This reaction is conducted at a temperature not below 75°C,
preferably from 75 – 85°C. Subsequent reaction with acetaldehyde diethyl acetal,
5 followed by solvent recovery, addition of dichloromethane, basification with
sodium hydroxide solution, layer separation, and treatment of the dichloromethane
layer with aqueous sulfuric acid, layer separation, aqueous layer treatment with
sodium hydroxide solution, product extraction with toluene and solvent recovery
produce racemic Cevimeline base.
10 This racemic Cevimeline base prepared in situ is then treated with IPA.HCl in fourth
solvent isopropyl alcohol. After solvent recovery and product crystallization in
cyclohexane, Racemic Cevimeline Hydrochloride Hemihydrate (CVM-II) is
produced.
In stage 3, various acids as well as solvents were tried under different experiments
15 which included p-toluene sulfonic acid monohydrate, conc. Sulfuric acid, methane
sulfonic acid and isopropyl alcohol hydrochloride. Surprisingly isolable product
was not obtained when methane sulfonic acid and conc. Sulfuric acid are employed
and the reactions produced sticky mass. p-toluene sulfonic acid monohydrate and
Isopropyl alcohol hydrochloride provided Racemic Cevimeline Hydrochloride
20 Hemihydrate with a purity greater than 90 and 95 % respectively. To the Thio acetic
acid salt of 3-hydroxy-3-acetoxymercapto methyl quinuclidine in a Isopropyl
alcohol is added IPA.HCl while maintaining temperature below 35°C. Then the
temperature is raised to at least 75°C, preferably from 75 - 85°C and maintained for
3 – 3.5 hrs.
25 Thioacetic acid salt of 3-hydroxy-3-acetoxymercapto methyl quinuclidine and
Isopropyl alcohol hydrochloride are used in a mole ratio of from 1:3 – 1: 4, more
particularly mole ratio of 1:3.5 is found most suitable.
Suitable solvent is isopropyl alcohol. It has been surprisingly found that very few
solvents like ethanol, isopropanol and Dysol (ethanol 90 % + toluene 10 %) support
30 reaction of step 3. Water and methanol produced some sticky mass which could not
28
be processed further. Employing 6 - 12 volumes of Isopropyl alcohol as a third
solvent provided purer product in step 4 which is Racemic Cevimeline
Hydrochloride Hemihydrate in good yields.
After, 3-hydroxy-3-mercaptomethyl quinuclidine is produced in situ, the reaction
5 mixture is cooled to 25 -35°C and then acetaldehyde diethyl acetal is introduced
slowly. Then the temperature of the reaction mixture is raised again to 75 - 85°C
and maintained for 3-4 hrs. During stirring, a sample of the reaction mixture is
removed every hour and is subjected to HPLC analysis to estimate the content of 3-
hydroxy-3 acetoxymercapto methyl quinuclidine (by % area) to ensure completion
10 of reaction.
Reaction temperature of 75-85°C is crucial. When different lower temperatures
were tried, following outcome as provided in table 5 was observed.
Table 5
Sr. No. Temperature Outcome
1 45 – 50°C Reaction was incomplete and 22.38% CVM-1 was
found after 2. 5 hrs. Product could not be isolated and
sticky mass is obtained.
2 55 – 60°C Reaction was incomplete and 5.51 % CVM-1 was
found after 2. 5 hrs. Product could not be isolated and
sticky mass is obtained.
3 65 – 70°C Reaction completed but sticky mass was observed.
15 Any unreacted CVM-I intermediate in the reaction mass will be further converted
into CVM-II in subsequent operations. This has been verified through multiple
batches at a commercial scale.
In few trial experiments, different mole ratios of acetaldehyde diethyl acetal were
employed in stage-3. All mole ratios from 1:3 to 1: 6 (1 part of thioacetic acid salt
20 of 3-hydroxy-3-acetoxymercapto methyl quinuclidine and 3 – 6 parts of
acetaldehyde diethyl acetal) produced Racemic Cevimeline Hydrochloride
Hemihydrate with a purity greater than 90 % with higher yield.
29
Reaction using acetaldehyde diethyl acetal is followed by solvent recovery of
isopropyl alcohol by distillation. Further work up process involves addition of
dichloromethane from 6 – 12 volumes at a temperature not exceeding 40°C. Adding
10 Volumes of dichloromethane is found most suitable to later produce Racemic
5 Cevimeline Hydrochloride Hemihydrate (CVM-II) of higher purity.
After adding dichloromethane, re-basification with sodium hydroxide solution is
commenced using 25.0% aqueous NaOH solution employed in 6 – 12 volumes.
This is followed by layer separation of dichloromethane layer and treatment of the
dichloromethane layer with aqueous sulfuric acid employed as 5 % aqueous
10 solution employed in from 6 – 12 volumes and again layer separation and aqueous
layer treatment with sodium hydroxide solution. This is followed by product
extraction with toluene in 6 – 12 volumes and solvent recovery producing racemic
Cevimeline base.
pH adjustment is crucial at the time of racemic Cevimeline base extraction in
15 toluene. pH should be adjusted in alkaline pH range from > 7.5 - <13.5 to obtain
desired quality and optimum yield of CVM-II. Preferably, pH should be adjusted
above 11.5. The most preferred pH range is from 11.5 – 12.5 to give desired purity
and optimum yield (best mode pH). Purity in this pH range is ≥ 95 % such as ≥ 98
%. Below, 11.5 and above 13.5, purity is ≥ 90 % - ≤ 95 % and yield is relatively
20 lower.
In a fourth step, Racemic Cevimeline base is treated with isopropyl alcohol
hydrochloride in isopropyl alcohol, followed by another solvent recovery step. The
product is finally crystallized in cyclohexane, resulting in the formation of the
Racemic Cevimeline Hydrochloride Hemihydrate. Preferably, from 4 – 10 volumes
25 of cyclohexane are employed. Diisopropyl ether is used as an alternative to
cyclohexane as both produced Racemic Cevimeline Hydrochloride Hemihydrate of
high purity (> 95 %).
Drying of Racemic Cevimeline Hydrochloride Hemihydrate
30
Racemic Cevimeline hydrochloride is dried at a temperature of from 40 – 65°C,
preferably at 50 – 60°C to obtain at least 90 %, preferably at least 95 % pure
product.
Stage-III: Preparation of Cis Cevimeline Para nitro benzoic acid salt (CVM5 III)
Reaction scheme-III:
N
O
S
CH3
Racemic Cevimeline hydrochloride
hemihydrate
Stannic chloride,
Dichlormethane
Aq.NaOH
N
O
S
CH3
. HCL.1/2 H2O
Aq.H2SO4
Purified water
Toluene
IPA.HCl
(2R,2'R)-2'-methylspiro[4-azabicyclo
[2.2.2]octane-2,5'-[1,3]oxathiolane]
Cis Cevimeline base (95:5)
+
Cis-Cevimeline para nitro benzoic acid salt- (CVM-III)
(99.5 : 0.5)
(1) Acetone
(2) Purification in Purified water
N
+
O
- O
O OH
Para-Nitrobenzoic acid
N
+
O
- O
O OH
N
O
S
CH3
Isomerization
.
10 Detailed process is provided under example 3.
Racemic Cevimeline hydrochloride hemihydrate is reacted with stannic chloride
and IPA.HCl in dichloromethane as a solvent. After quenching the reaction in water
and undergoing a series of layer separations, treatments, and pH adjustments, the
Cis Cevimeline base is produced. This base is then reacted with p-nitrobenzoic acid
15 in acetone to yield a crude form of the Cis Cevimeline para-nitrobenzoic acid salt.
Further purification in purified water produces the Cis Cevimeline paranitrobenzoic acid salt (CVM-III).
Few other solvents other than Dichloromethane were tried including dichloroethane
and chloroform. The reaction in chloroform produced 2.16 % trans isomer and
20 hence undesirable. Dichlroethane produced lower yield than dichloromethane
although levels of trans isomer was acceptable.
31
Dichloromethane used in volumes from around 10 – 12 (i.e. 10 – 12 litres for 1 kg
of CVM-II) provided optimum yields.
Isopropyl alcohol hydrochloride is used from 0.1 volume to 0.4 volumes i.e. from
0.1 – 0.4 kg for 1 kg of CVM-II. All these volumes controlled trans isomer but best
5 yield is obtained for 0.3 volumes of Isopropyl alcohol hydrochloride.
CVM-II and Stannic chloride are employed in molar ratio of 1:1 to 1:2, preferably,
from 1:>1 to 1:7. At 1:1 molar ratio, trans isomer is found to be higher than 0.5 %.
Best ratio is found to be around 1:1.5 where trans isomer is controlled below 0.3
and optimum yield is obtained.
10 Stannic chloride is added at a lower temperature of not more than 15°C such as 10-
15°C, preferably not more than 5°C such as 0-5°C, more preferably not more than
0°C such as -5 – 0°C and most preferably not more than -5°C such as -5– -10°C.
Trans isomer is controlled in all of the above ranges but optimum yield is produced
when Stannic chloride is added at a lower temperature of -5– -10°C.
15 In stage-III, isomerization reaction is carried out at various temperatures selected
between 20-40°C such as 20-25°C, 25-35°C, 35-40°C. Best yield is obtained when
reaction temperature is preferably from 25-35°C.
During work up of the reaction, pH is adjusted between 10 – 14 such as from 10 –
11, from 11.5 – 13.5, above 13.5 etc. Best yield is obtained when pH is adjusted
20 between 11.5 – 13.5.
During work up of the reaction, 5 % aq. Sulfuric acid solution is used for acidic pH
adjustment. Amount of Sulfuric acid solution employed is from 6 volumes to 12
volumes such as 6, 8, 10 and 12 volumes. Best yield is obtained when 10 volumes
of 5 % aq. Sulfuric acid solution is employed.
25 Toluene which is employed to extract product during work up can be used from 6
volumes to 12 volumes. 10 volumes of Toluene has been found sufficient for
product extraction.
Cis Cevimeline salts with different acids
30 Although, p-nitro benzoic acid is a most preferred salt of Cis Cevimeline, inventors
have tried following salts,
32
i) Sulfate salt prepared using Conc. Sulfuric acid;
ii) Methane sulfonic acid salt using Methane sulfonic acid;
iii) Camphor sulfonic acid salt using DL-camphor sulfonic acid;
iv) p-toluene sulfonic acid salt using p-toluene sulfonic acid.
5 Following results as shown in table 3 below were obtained emphasizing selection
of p-nitro benzoic acid.
Table 3 - repeated
Sr. No. Acid Salt Purity and Impurities
1. Conc.
H2SO4
Cis Cevimeline
sulfate salt
Cis isomer = 95.72 %; trans isomer
4.28 %;
CVM- impurity 1 0.27 %, CVMimpurity 2 in 0.28 %
2. Methane
sulfonic
acid
Cis Cevimeline
methane sulfonic
acid
Cis isomer = 96.93 %; trans isomer
3.07 %;
CVM- impurity 1 0.10 %, CVM-2
impurity in 0.17 %
3. DLcamphor
sulfonic
acid
Cis Cevimeline
camphor sulfonic
acid salt
Cis isomer = 97.47 %; trans isomer
2.53 %;
CVM- impurity 1 0.14 %, CVM
impurity -2 in 0.02 %;
CVM RRR – 0.19 %;
CVM RRS – 0.25 %;
4. p-nitro
benzoic
acid
Cis Cevimeline pnitro benzoic acid
salt
Cis isomer = 99.86 %; trans isomer
0.14 %;
No other impurities were observed.
5. ptoluene
sulfonic
acid
Product could not be isolated
33
Pursuant to selection of p-nitro benzoic acid for preparing Cis Cevimeline
Hydrochloride p-nitro benzoic acid salt, few other impurities are also checked and
controlled as per ICH M7 guideline.
Additional controlled impurities by HPLC include
5 i) 2-Nitro Benzoic Acid
ii) 2,4 Dinitro Benzoic Acid
iii) 4-Nitro Benzoic Acid
iv) 3-Nitro Benzoic Acid
v) 3,4 Dinitro Benzoic Acid
10 vi) 4-Niro Toluene.
Cis Cevimeline p-nitro benzoic acid salt preparation was optimized for
i) mole ratio of para nitrobenzoic acid used for Cis cevimeline p-nitro
benzoic acid salt preparation
15 Many mole ratios of para nitrobenzoic acid to Cis cevimeline base were
tried. Four most suitable ones are 0.9, 0.94, 1.0 and 1.05. All these
ratios produced Cis cevimeline p-nitro benzoate with acceptable levels
of trans isomer. A ratio of 0.94 gave the best yield.
ii) Different volume of acetone used for Cis cevimeline p-nitrobenzoic acid
20 salt isolation.
Different volumes of acetone such as 3, 4, 5 and 6 were tried. Volume
5 gave the best yield.
iii) Filtration temperatures for filtering Crude Cis cevimeline pnitrobenzoic acid salt.
25 At least 4 different filtration temperatures were tried including 0-5°C, 5
– 10°C, 15-20°C and 25 – 35°C. While all temperatures controlled trans
isomer, best yield is produced when filtration temperature was from 0-
5°C.
iv) Purification of Cis cevimeline p-nitrobenzoic acid salt using different
30 solvents.
34
Various solvents such as acetone, methanol, purified water, toluene and
cyclohexane were tried. Methanol and Purified water provided best
purity. Cyclohexane and toluene produced a product having higher trans
isomer.
5 v) Purification using different volumes of purified water;
minimum 2.0-5.0 volumes of purified water produced desired
quality and optimum yield of CVM-III. 4-volume was recommended
for ease of physical operation.
vi) Purification by heating at different temperature. Different temperatures
10 from 50 – 90°C were tried including 50-55°C, 60-65°C, 70-80°C and
80-90°C. All conditions favoured high quality product in optimum
yields.
vii) Different maintaining time before product isolation.
Different maintaining times before product isolation were employed
15 from 30 mins – 300 mins including 30 mins, 60 mins, 120-180 mins,
240 mins and 300 mins. While maintaining time did not affect the
purity, better yield was obtained when maintaining time was from 120 –
180 mins.
viii) Different drying temperatures.
20 Different drying temperatures from 35-75°C were tried including 35-
40°C, 45-55°C, 60-70°C and 70-75°C. No significant impact was found
on the purity or yield but least trans isomer was found when drying was
conducted between 45-55°C.
ix) Different product isolation temperatures.
25 Different product isolation temperatures were tried from 0°C – 35°C
such as 0-5°C, 5-10°C, 10-15°C and 25-35°C. Trans isomer was below
0.5 % at all conditions but was minimum when a temperature of 5-10°C
was employed during product isolation.
30 Structure Elucidation and Characterization of Cis Cevimeline Para
nitrobenzoic acid salt
35
The Structure Elucidation and characterization of Cis Cevimeline Para nitrobenzoic
acid salt was established by analytical technique such as FT-IR, LC-MS/MS, 1H
NMR and 13C NMR. The purity of impurity was determined by HPLC.
5 Common Name: Cis Cevimeline Para nitrobenzoic acid salt
Chemical Name: (2R,2'R)-2'-methylspiro [4-azabicyclo [2.2.2] octane-2,5' [1,3]
oxathiolane] 4-nitrobenzoic acid (1:1)
Structure: -
16
15
17
14
18
19
N
+
20 O
-
24
O
21
O 22 25
OH
23
3
6
10
N
7
9
8
12
11
2
O
4
S
1
5
CH3
13
.
10
Molecular Formula = C17H22N2O5S
Formula Weight = 199.31, 167.11 g/mole Total weight = 366.43 g/mole
The Chromatographic purity of Cevimeline Para nitrobenzoic acid salt was
15 performed by High Performance Liquid Chromatography (HPLC) using In-house
test procedure.
Cis isomer: 99.89% and HPLC purity: 99.97%
Characterization by Nuclear Magnetic Resonance Spectrometer The
20 characterization of Cevimeline Para nitrobenzoic acid salt was performed by
400MHz Nuclear magnetic resonance spectrometer (NMR). It was analyzed for
proton (1H) and 13 C NMR experiments by preparing samples in CDCl3.
Assignment
25 1H NMR (In CDCl3)- 400 MHz
 (ppm) Relative protons Proton Assignment
36
1.578-1.604 3 13
1.604-1.779 1 10
1.844-2.034 2 11
2.147-2.414 2 9
3.134-3.310 6 6,8,12
3.332-3.469 2 2
5.168-5.208 1 5
8.141-8.234 4 15.16,18,19
9.001 1 23
Total Hydrogen = 22
13C NMR (In CDCl3)- 400 MHz
 (ppm) Carbon Assignment
19.06 13
21.08 9
22.75 11
27.20 2
39.63 10
45.01 8
45.44 12
57.67 6
80.60 5
84.85 3
37
123.04 15,19
130.27 16,18
142.10 17
149.19 14
170.82 22
Total carbon = 17
Infrared Spectrum:
The Infrared spectra of Cevimeline Para nitrobenzoic acid salt was performed using
Shimadzu IR Affinity-1S using inhouse ATR method at Kalintis Healthcare Pvt.Ltd.
5 The IR spectra graphs are attached below.
FT-IR Frequency for Cevimeline Para nitrobenzoic acid salt. Approx. Frequency
cm-1 Assignment 3471.87 -O-H Stretching, 2931.80 -C-H Stretching, 1641.42 -
C=O stretching, 1510.26 -N-O stretching nitro compound, 1454.33 -C-H bending
(methyl group) 1365.60-1469.76, -O-H bending 1099.43-1153.43, -C-O stretching
10 1006.84-1028.06, -O-H bending 819.75-877.61, -C-H bending 1,4 substitutions,
709.80-796.60 -C-H bending.
Characterization by Mass Spectrometry
The characterization of Cevimeline Para nitrobenzoic acid salt was performed by
15 Mass. It was analyzed for the Mass in +ve mode.
Mass Results,
Molecular weight of Cevimeline base: 199.31 g/mole, Molecular weight of Para
nitrobenzoic acid: 166.11 g/mole, m/z value of Cevimeline base: 200.05 [M+H] +
and m/z value of para nitro benzoic acid,165.92 (M-H)-
20 Note: During mass analysis, Cevimeline para nitro benzoic acid salt split down into
Cevimeline base and para nitrobenzoic acid, hence individual m/z value obtained
in positive and negative region.
38
Conclusion: - On the basis of above spectral data (FT-IR, LC-MS/MS, 1H NMR
and 13C NMR) analysis, the structure of Cevimeline Para nitrobenzoic acid salt,
(2R,2'R)-2'- methylspiro [4-azabicyclo [2.2.2] octane-2,5' [1,3] oxathiolane] 4-
nitrobenzoic acid (1:1) was confirmed.
5
Figures 8 - 11 provide data on the characterization of Cis Cevimeline p-nitro
benzoic acid salt. Figure 8 provides an IR spectra, figure 9 provides a LC-MS/MS
Mass Spectra, figure 10A – 10C provide 1H NMR / proton NMR spectra, figures
11A – 11C provide 13C NMR spectra of Cis Cevimeline p-nitro benzoic acid salt.
10
Stage-IV: Preparation of Cis Cevimeline Hydrochloride
Reaction scheme:
Cyclohexane, Carbon
Cis-Cevimeline hydrochloride-(99.7:0.3)
. HCl.1/2 H2O
Purified water Aq.NaOH
Cis-Cevimeline para nitro benzoic acid salt- (CVM-III)
N
O
S
CH3
N
+
O
- O
O OH
IPA + IPA.HCL
Recrystalization in
IPA+Cyclohexane
.
N
O
S
CH3
Detailed process is provided under example 4.
15 In stage-IV, Cis-cevimeline organic acid salt is subjected to a series of treatments
such as basification, extraction, carbon treatment, filtration and finally treated with
isopropyl alcohol hydrochloride to produce Cis-Cevimeline Hydrochloride of high
chemical purity, high isomeric purity, and desired particle size.
20 Process for manufacturing of Cis Cevimeline Hydrochloride by breaking of Cis
cevimeline para nitrobenzoic acid salt with sodium hydroxide solution and
extraction with cyclohexane followed by isolating Cis Cevimeline Hydrochloride
by adding IPA.HCl followed by recrystallization with Cyclohexane and isopropyl
alcohol produce crystalline material with desired particle size
25
Following optimizations were applied in the above process.
i) Different volume of purified water for salt breaking.
39
Different volumes of water including from 2 volumes to 4 volumes were
tried for salt breaking. 3 volumes was found the best in providing
desired quality and optimum yield of Cis Cevimeline Hydrochloride.
ii) Different pH conditions for salt breaking.
5 Different pH conditions were tried for salt breaking including from pH
10 - > 13.5. pH had no impact on trans isomer and other impurities,
however, pH from 11.5 – 13.5 was found sufficient to break down
Cevimeline para nitrobenzoate salt to produce desired quality and
optimum yield of Cis Cevimeline Hydrochloride.
10 iii) Different solvents for Cevimeline base extraction.
Different solvents were employed for extraction of Cevimeline base
such as diisopropyl ether, cyclohexane, toluene, dichloromethane and
ethyl acetate. Product could not be isolated when Dichloromethane is
used for extraction. Lower yield was obtained with ethyl acetate. Best
15 solvents were diisopropyl ether and cyclohexane. However, DIPE has
a tendency to generate peroxide upon storage which could potentially
lead to the formation of the Cevimeline sulfoxide impurity, making it a
less advisable choice. Hence cyclohexane was the best solvent.
iv) Different volume of cyclohexane for Cevimeline base extraction and
20 product isolation.
v) Different quantity of Activated carbon.
Different quantities of activated carbon from 3 – 10 % such as 3 %, 5
%, 7% and 10% were employed. Quantity of activated carbon did not
have any impact on purity and yield of the product. A minimum of 5.0%
25 w/w carbon is preferred to get the desired decription of Cevimeline
hydrochloride.
vi) Different mole ratio of IPA.HCL used for product isolation.
Different mole ratios of IPA.HCL including from 0.9 to 1.10 were tried
such as 0.9, 0.95, 0.98, 1.0 and 1.1. All mole ratios produced desired
30 quality product with controlled trans isomer and no other impurities
were found. A mole ratio of 0.98 was chosen.
40
vii) Different addition time of IPA.HCl for product isolation.
Different addition time of IPA.HCl were tried from fast addition
(dumping), addition over 30 mins, addition over 60 mins. etc. Since this
5 is an exothermic reaction, addition over an extended period of more than
60 min. is preferred.
viii) Different maintaining time at 5-10°C.
Different maintaining times at 5-10°C after IPA.HCl addition in
Cevimeline base solution were tried from 30 mins to 300 mins.
10 Maintaining time of from 90-120 min is found sufficient to produce the
desired results.
ix) Different Drying temperatures for drying API under vacuum.
Various temperatures were employed for drying from 40-80°C such as
40-50°C, 50-60°C, 60-70°C and 70-80°C. Drying temperature did not
15 affect purity or levels of trans isomer. However, to avoid overdrying, a
drying temperature was selected as 50-60°C.
x) Different temperatures of addition of IPA.HCL.
Different temperatures were tried from 0-15°C such as 0-5°C, 5-10°C
and 10-15°C. It is surprisingly found that as temperature increases trans
20 isomer increases and when temperature is above 10°C, trans isomer
increases beyond acceptable levels. Therefore, 0-5°C is chosen as a safe
temperature at which addition of IPA.HCl
xi) Solvent treatment of Cevimeline Hydrochloride to get desired particle
size.
25 It is an aspect of the invention to produce Cis Cevimeline Hydrochloride
of desired particle size. It is surprisingly noted that solvent treatment
such as slurring and crystallization significantly impact particle size of
Cis Cevimeline Hydrochloride.
Different solvents are used for crystallization such as polar solvents and
30 a combination of polar and non-polar solvents. It is possible to obtain
particle size from D90 = 25 µm (90 % particles have size below or up
41
to 25 µm, preferably up to 20 µm and more preferably up to 15 µm ) to
D90 = 100 µm (90 % particles have size below or up to 100 µm,
preferably up to 80 µm and more preferably up to 75 µm) merely by
slurring or choosing certain solvent(s) of crystallization (refer figures
5 7A and 7B). Similarly, it is possible to obtain following particle size
distribution Using dissolving Cis Cevimeline Hydrochloride in
isopropyl alcohol and precipitating using cyclohexane.
D10: not more than 20µm, preferably not more than 10 µm and more
10 preferably not more than 7.5 µm;
D50: not more than 50µm; preferably not more than 30 µm and more
preferably between 10 µm - 25 µm;
D90: not more than 100 µm, preferably not more than 80 µm, most
preferably not more than 75 µm.
15
Table 6 provides results of particle size according to selection of
different solvents.
Table 6
Sr. No. Solvent Particle size
1 IPA (slurry) D10: 2.03 µm
D50: 5.33 µm
D100: 11.59 µm
2 Ethyl acetate (slurry) D10: 2.68 µm
D50: 8.06 µm
D100: 57.19 µm
3 Slurry having 50 % ethyl acetate +
50 % cyclohexane
D10: 1.64 µm
D50: 3.96 µm
D100: 8.01 µm
42
4 Dissolved in a 5 volumes of
isopropyl alcohol and isolated by
adding 16 volumes of cyclohexane
D10: 2.49 µm
D50: 8.71 µm
D100: 63.97 µm
5 Dissolved in a 6 volumes of
isopropyl alcohol and isolated by
adding 16 volumes of cyclohexane
D10: 2.66 µm
D50: 9.99 µm
D100: 59.30 µm
6 Dissolved in a 4 volumes of
isopropyl alcohol and isolated by
adding 10 volumes of cyclohexane
D10: 3.70 µm
D50: 12.80 µm
D100: 62.11 µm
Stability Studies
Three large scale validation batches were manufactured as per process described
under examples 1 – 4 and Cis Cevimeline Hydrochloride is so produced was
5 subjected to long term stability testing (at 25°C / 60 % RH) and accelerated stability
testing (at 40°C / 75% RH). Samples were removed from respective conditions at
the initial (beginning), 1 month, 2 months, 3 months and 6 months and were tested
for the following
i) Description.
10 ii) Identification by a) IR and b) HPLC.
iii) Water content by KF
iv) Content of chloride.
v) Assay by HPLC.
vi) Organic impurities by HPLC wherein trans isomer impurity is estimated by
15 method 1 and other impurities are estimated using method 2.
The details of all results on one batch are as follows:
43
Table 7 - Condition – 40°C / 75 % RH
5
44
Table 7 - Condition – 40°C / 75 % RH
5
45
Table 7 - Condition – 40°C / 75 % RH
5
46
Table 7 - Condition – 40°C / 75 % RH
5
47
Table 7 -Condition – 40°C / 75 % RH
48
Table 8 - Condition – 25°C / 60 % RH
5
49
Table 8 - Condition – 25°C / 60 % RH
5
50
Table 8 - Condition – 25°C / 60 % RH
5
51
Table 8 - Condition – 25°C / 60 % RH
5
52
Table 8 - Condition – 25°C / 60 % RH
53
Advantage of Current process:
Stage-I: Preparation of Thio acetic Acid Salt of 3-hydroxy-3-acetoxymercapto
methyl quinuclidine.
5 Process for manufacturing of Thio acetic Acid Salt of 3-hydroxy-3-
acetoxymercapto methyl quinuclidine according to the present invention involves
reaction using Quinuclidinone hydrochloride and trimethyl sulfoxonium iodide at
preferably 0-10°C in dimethyl sulfoxide as solvent. Potassium tert-butoxide is
added in this reaction. It is most preferably divided into a few equal parts from 2 –
10 6 depending on the weight to be added and added in 2 – 6 equal portions parts / lots,
preferably, 4 – 5 equal portions at 0-10°C. The mixture was stirred for an additional
2-3 hours at 0-10°C followed by workup. The , epoxide intermediate formed insitu
is extracted in 20 volume toluene and then reacted with thio acetic acid to produce
Thio acetic Acid Salt of 3-hydroxy-3-acetoxymercapto methyl quinuclidine. The
15 product filtration is done at 0-10°C.
Advantage:
(1) In the earlier reported process, after carrying out the reaction at 0-5°C, the
reaction mixture was maintained at room temperature for 16 hrs followed by
20 work up process. The epoxide intermediate which was prepared insitu was
extracted in 10 volume toluene, and then reacted with thio acetic acid. The product
filtration was also conducted at room temperature. Exposing reaction mixture to
room temperature for a longer time as well as carrying out product filtration at room
temperature together with using low volumes of solvent toluene for extraction
25 impacted yield of the product, Thio acetic Acid Salt of 3-hydroxy-3-
acetoxymercapto methyl quinuclidine which is produced in overall 36.72% molar
yield.
In the current process according to the present invention, reaction temperature as
well as work-up temperature were controlled and product filtration is also
30 conducted at 0-10°C. Also, a higher volume of toluene was used (20 volumes as
54
against 10 volumes of prior art). to produce Thio acetic Acid Salt of 3-hydroxy-3-
acetoxymercapto methyl quinuclidine with overall 61-67% molar yield.
Controlling reaction temperature and increasing the volume of toluene for
extraction did not impact the cost of production as yield obtained is almost doubled
5 which reduced the overall cost of production of Cevimeline hydrochloride.
Stage-II: Preparation of Racemic Cevimeline Hydrochloride Hemihydrate
(CVM-II).
Process for manufacturing of racemic cevimeline hydrochloride according to the
10 present invention comprises i) reacting Thio acetic acid salt with IPA.HCl and
acetaldehyde diethyl acetal in Isopropyl alcohol followed by ii) workup in acidic
and basic conditions; iii) extracting racemic cevimeline base with toluene (10-
volume) and finally iv) hydrochlorination using IPA.HCl, and isolation in
cyclohexane. This process produced racemic cevimeline hydrochloride with an
15 80% yield.
Advantage:
(1) In an earlier reported process, racemic cevimeline hydrochloride was
produced by reacting Thio acetic acid salt with p-toluene sulfonic acid
monohydrate as organic acid and acetaldehyde diethyl acetal in Isopropyl alcohol
20 followed by workup in acidic and basic condition. The racemic cevimeline base
was extracted with heptane (50 volume) and solvent was distilled to produce crude
racemic cevimeline base.
By modification and optimisation of the reported process, it is possible to avoid use
25 of p-toluene sulfonic acid monohydrate which is expensive that IPA.HCl and
hazardous in nature and a potential genotoxic compound. Hence, current process
employs safer and more economical reactant that the reported process.
30
55
Stage-III: Cis Cevimeline Para nitro benzoic acid salt
Advantage of current process using organic acid (p-Nitrobenzoic acid).
The process for manufacturing of Cis cevimeline Para nitrobenzoic acid salt
comprises i) first isomerising racemic cevimeline hydrochloride (65:35 cis and
5 trans ratio) using metal catalyst (stannic chloride) into Cis cevimeline base that
contains up to 5 % , more preferably from 0.5-5.0 % trans isomer. Then this base is
further converted into Cis cevimeline Para nitro benzoic acid salt using para nitro
benzoic acid in acetone. Further process involves recrystallisation of Cis
Cevimeline para nitrobenzoic acid salt in purified water to produce high quality of
10 Cis Cevimeline para nitrobenzoic acid salt having a) no Trans isomer or Trans
isomer in an amount of less than 0.30% and b) all specified organic impurities
below 0.15%; and c) unspecified impurities below 0.10%.
Advantage:
15 (1) No process reported earlier, mentions isomerising racemic cevimeline
hydrochloride into Cis Cevimeline base and converting the said base to Cis
Cevimeline para nitrobenzoic acid salt.
(2) In an earlier reported process, Racemic Cevimeline base (having 65:35 Cis
and Trans ratio) was directly converted into Cis Cevimeline Para nitro
20 benzoic acid salt using Para nitrobenzoic acid without isomerisation of
racemic cevimeline. Hence, around 50% or more is lost in mother liquor.
While in the process according to the present invention, first isomerisation is
performed to produce Cis cevimeline base (97:3 Cis and Tans ratio) in situ which
is converted into Cis cevimeline Para nitrobenzoic acid salt and further process
25 involved removing 3.0% trans isomer so that Trans isomer is either absent or is in
amount of up to 0.3%. Further advantage of this salt preparation is restricting a) all
specified organic impurities below 0.15% and b) unspecified impurities below
0.10%. This process enables production of a highly pure intermediate before
producing a high quality drug substance.
30 Conducting a first isomerisation of Racemic Cevimeline base (having 65:35 Cis
and Trans ratio) before salt preparation enables conversion of unwanted 35% trans
56
Cevimeline isomer into Cis Cevimeline Base with up to 3-5% trans Cevimeline
isomer. Cis Cevimeline Base is converted in situ into Cis cevimeline para
nitrobenzoic acids salt with almost qualitative yield which reduced overall cost too.
5 By modification and optimisation of the reported process, current process achieves
high yield of 65-70% as against the reported yield of 28.72 % and no or low amount
of trans isomer impurity which is not more than 0.30% as against 1.70 % of trans
isomer impurity reported previously.
10 The current process has several advantages such as economic viability, and it is
easy to scale up and to reduce huge amounts of industrial waste.
Stage-IV : Cis Cevimeline Hydrochloride
Advantage using Cyclohexane and Isopropyl to get the desired particle size.
15 The current process for manufacturing of Cis Cevimeline Hydrochloride by
breaking cis cevimeline para nitrobenzoic acid salt with sodium hydroxide solution
and extraction with cyclohexane followed by isolating Cis Cevimeline
Hydrochloride by adding IPA.HCl which is recrystallised using Cyclohexane and
isopropyl alcohol to produce crystalline material with desired particle size.
20 Alternatively, isopropyl alcohol slurry is used to achieve finer particle size.
Advantage:
(1) In earlier reported processes, n-hexane, DIPE are used as solvents to extract
the Cis cevimeline base, which is converted into Cis Cevimeline hydrochloride
25 using IPA.HCl while in the current process cyclohexane is used as a solvent to
extract Cis cevimeline base, which is converted into Cevimeline hydrochloride
using IPA.HCl. N-hexane is highly flammable, while DIPE tends to generate
peroxide on holding. This peroxide might generate Cevimeline sulfoxide impurity
whenever peroxide comes in contact with the solvent itself. It is difficult to
30 eliminate the Cevimeline sulfoxide impurity once it is generated. Compared with
57
N-hexane and DIPE as solvents, cyclohexane is less flammable, does not facilitate
formation of peroxide and sulfoxide and is easy to handle at a commercial scale.
Additionally, the current process of recrystallisation of Cevimeline Hydrochloride
5 employs different solvents to generate Cis Cevimeline Hydrochloride of different
desired particle sizes. Preferably, it is dissolved in Isopropyl alcohol followed by
the addition of Cyclohexane, which produces Cis Cevimeline hydrochloride having
the desired particle size mentioned in the tables 9A and 9B below.
Table 9A: Desired particle size using solvent / antisolvent
d10
Not more than 20 µm preferably not more than 10 µm, more
preferably not more than 7.5 µm, most preferably Between
1.0 and 7.5 µm
d50
Not more than 50 µm, preferably not more than 30 µm, more
preferably not more than 25 µm, most preferably Between
10.0 and 25.0 µm.
d90
Not more than 100 µm, preferably not more than 80 µm, more
preferably not more than 75 µm, most preferably Between
30.0 and 75.0 µm.
10
Additionally, if a lower particle size distribution is desired, isopropyl alcohol slurry
can be used, which provides the following particle size distribution.
Table 9B: Desired particle size using slurrying
d10
Not more than 10 µm preferably not more than 7.5 µm, more
preferably not more than 5 µm, most preferably Between 1.0
and 5 µm
d50
Not more than 30 µm, preferably not more than 20 µm, more
preferably not more than 15 µm, most preferably Between 1.0
and 10.0 µm.
58
d90
Not more than 50 µm, preferably not more than 30 µm, more
preferably not more than 20 µm, most preferably Between 5.0
and 15.0 µm.
The Cis Cevimeline Hydrochloride prepared in accordance with the present
invention is a high-quality product with trans isomer of less than 0.30%, any
specified impurity in an amount of not more than 0.15 % and any unspecified
5 impurity in an amount of not more than 0.1%. Cis Cevimeline Hydrochloride
produced by this improved and scalable process is stable in accelerated and longterm storage conditions.
Other advantage:
10 It is also difficult for a single method to detect all impurities. It is observed that a
method employed and known for estimating trans impurity in Cis Cevimeline
Hydrochloride, referred to as method I or Method 1, fails to resolve and estimate
all other impurities.
Accordingly, a second method referred as Method II or Method 2 has been
15 developed to ensure that all probable impurities are resolved and can be estimated.
A system suitability test ensured the resolution and estimation of other impurities.
Method II or 2 by HPLC
Reagents:
Water HPLC grade or equivalent
20 Dipotassium hydrogen phosphate
Sodium Hydroxide
Acetonitrile
Methanol
1 N Sodium hydroxide solution:
25 4 gm of sodium hydroxide is weighed and transferred in 100 mL of water. It is
sonicated to dissolve and mixed well.
Sodium hydroxide
59
Another 2.5 g sodium hydroxide is weighed and dissolved in 25 mL of water or
alternate volumes can be prepared if required.
Diluent:
900 mL of water and 100 mL of methanol are mixed, sonicated to degas, and
5 mixed well.
Preparation of Buffer solution:
Weighed and transferred 5.4 g of Dipotassium hydrogen phosphate in water and
mixed to dissolve solids. The pH of the solution is adjusted to 10.0 ± 0.2 with a
controlled addition of sodium hydroxide (2.5 g in 25 ml) and mixed well.
10 Preparation of Mobile Phase-A:
To prepare mobile phase A, 1000 mL of buffer and 5mL of acetonitrile are mixed,
sonicated to degas, and mixed well, or alternate volumes can be prepared if
required.
Preparation of Mobile Phase-B:
15 To prepare 1000 ml of mobile phase B, 300 mL of buffer and 700 ml of
acetonitrile are mixed, sonicated to degas, and mixed well or alternate volumes
can be prepared if required.
HPLC Chromatographic Parameters:
• Column: C18
20 • Detection: UV at 210 nm
• Run time: 70 minutes
• Gradient program – A suitable gradient program can be applied, for
example, from 0 – 12 minutes and from 60 – 70 mins – 100 % mobile phase A
and from 12th minute to 60 min, mobile phase A is gradually reduced from 100 –
25 20 % and mobile phase B is increased from 0 – 80%.
• Following RTs of the impurities 1 and 2 were observed.
Table 10:
Name RT
Cevimeline impurity-1: 29.70
60
3-(((1-((((1r,4r)-3 Hydroxyquinuclidin-3-yl) methyl) thio)
ethyl) thio) methyl) quinuclidin-3-ol.
Cevimeline impurity-2:
3-(((1-((((1s,4s)-3-Hydroxyquinuclidin-3-yl) methyl) thio)
ethyl) thio) methyl) quinuclidin-3-ol.
30.24
New impurities
The inventors, by using Method 2, identified two isomeric impurities never
5 reported before at the final stage of Cis Cevimeline Hydrochloride, namely 3-(((1-
((((1s,4s)-3-Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl)
quinuclidin-3-ol (Cevimeline impurity-1) and 3-(((1-((((1r,4r)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol
(Cevimeline impurity-2). These impurities are generated in an acidic environment
10 due to acid degradation; hence, their estimation is essential while producing
acceptable pharmaceutical salt. It is further essential to incorporate limits of these
two newly identified impurities in the final release specification of API with a limit
of not more than 0.15%. Due to their isomeric nature, their retention times are very
close. They have been found always together. These impurities have the following
15 structure.
Structure:

N
OH
N S
OH
S
CH3

N
OH
N S
OH
S
CH3
(Cevimeline impurity-1) (Cevimeline impurity-2)
20 (ss isomer) (rr isomer)
Molecular weight: 372.59 g/mole
The impurities were characterized and confirmed by spectral techniques like NMR,
Mass, and IR.
61
These two impurities elute out very closely and are found together. Generally, their
weight ratio is from 1:20 to 20:1, preferably from 1:10 to 10:1, and more preferably
from 1:7.5 to 7.5:1, and most preferably from 1:5 to 5:1 in most samples including
those that are degraded beyond acceptable levels.
5
The inventors were able to separate at least 75 %, preferably at least 80 %, more
preferably at least 85 %, and most preferably, at least 90 % pure mixture of CVM
impurity 1 and CVM impurity 2 as reported in Table 11 below.
10 Table 11: Successful separation of pure mixture of CVM impurity 1 and CVM
impurity 2
Figure % CVM impurity
1
% CVM impurity
2
% total impurity
(CVM impurity 1
+ CVM impurity
2)
17 A and 17B 21.82 68.74 90.56
18A and 18B 21.86 68.79 90.65
19A and 19B 21.90 68.83 90.73
Following tables 12 – 15 provide 1H and 13C NMR, characteristic peaks in FTIR
15 and Mass results
Table 12
62
Table 13
5
Table 14:
63
Table 15:
5
Cis cevimeline Hydrochloride is hydrochloride salt with hemihydrate form, hence
on storage, it may release traces of HCl and water already present in the
hemihydrate form; these two impurities are forms in acetic condition, hence to
control these two impurities as per ICH guideline, identification and
10 characterisation of these impurities are necessary with specified limit. These two
impurities are not reported in the prior art.
Experimental Details
The following examples illustrate the invention without limiting the scope of the
15 invention in any way.
Example 1
Stage-I: Preparation of Thioacetic Acid Salt of 3-hydroxy-3-acetoxymercapto
methyl quinuclidine (CVM-I).
64
Dimethyl sulfoxide (950.0 ml) is charged into a Round bottom flask, and 3-
Quinuclidinone hydrochloride (200.0 gm) and Trimethyl sulfoxonium iodide
(326.79 gm) are added while ensuring the temperature remains below 35°C. An
additional Dimethyl sulfoxide (50.0 ml) is flushed to ensure complete transfer. The
5 reaction mixture is cooled to 10 to 15°C. Potassium tert-butoxide (Part-1) (69.43
gm) is slowly introduced in reaction mass to maintain the temperature at 10 to 15°C,
all under a nitrogen atmosphere. After this addition, the reaction mass is chilled to
0 to 10°C and stirred for 15-20 minutes at this temperature. The subsequent
additions of Potassium tert-butoxide are continued (in equal portions / parts from 2
10 to 6, preferably 4 - 5, most preferably 5), adding 69.43 gm each time, ensuring the
temperature is maintained between 0 to 10°C. The reaction mass is stirred for 15-
20 minutes at the same temperature range under a nitrogen atmosphere after each
addition. After the final Part addition of Potassium tert-butoxide, the reaction mass
is stirred for an additional 1-3 hours at 0 to 10°C.
15 Confirmed the completion of reaction by GC analysis with following limit.
Determination of 3-Quinuclidinone hydrochloride content by GC (by % area) is
not more than 10.0 %, preferably not more than 5.0 % and most preferably not more
than 3.0 %
30% solution of Sodium Chloride (2000 ml) is slowly added to the reaction mass
20 through the addition pot, ensuring the temperature remains below 15°C. Then,
sodium chloride (200.0 gm) is added to the mixture, maintaining the temperature
below 15°C. The reaction mass is stirred for 10-15 minutes, Subsequently, toluene
(1600 ml) is added to the reaction mass, The mixture is stirred for an additional 20-
30 minutes, maintaining the temperature below 15°C.
25
Salt Filtration:
The inorganic salt is removed by filtration and washed with Toluene (400 ml).
Layer separation and Product extraction:
65
The filtrate is charged into RBF, the mixture is cooled below 15°C if necessary and
allowed to settle for 20 to 30 minutes. The bottom aqueous layer is separated from
the upper organic layer. The organic layer is transferred to a separate flask.
Next, the aqueous layer is charged in RBF. Charge Toluene (1000 ml) is added and
5 stirred for 20 to 30 minutes. The mixture is allowed to settle for another 20 to 30
minutes at the same temperature range. The bottom aqueous layer is separated from
the upper organic layer and the organic layer is transferred to the separate flask.
Repetition of the process: The aqueous layer is charged in RBF, toluene (1000 ml)
10 is added and stirred for 20 to 30 minutes, it is allowed to settle for 20 to 30 minutes,
the layers are separated, and the organic layer is transferred to the above mentioned
separate flask.
After these steps, all the organic layers are combined in the RBF, and stirred for 10
to 15 minutes. The mixture is allowed to settle for another 10 to 15 minutes, and
15 then aqueous layer if any is separated. Finally, the reaction mass is chilled to a
temperature range of 0 to 5°C.
Product Isolation:
Thioacetic acid (188.38 gm) is added slowly while maintaining the temperature
20 between 0-5°C. The reaction mass is stirred until the precipitation occurs, keeping
the temperature within the 0-5°C range. The reaction mass is maintained at this
temperature for 3 to 4 hours.
Product Filtration & Washing:
25 The product is filtered and washed with chilled toluene (400 ml). Then, the material
is unloaded.
Product drying
The material is dried under vacuum for 4 hours at a temperature of 40°C to 50°C in
30 vacuum dryer. Unload the material CVM-I, yield obtained in the range of range
200-250 gm (44.37-69.33% molar) based on input KSM.
66
After drying, a sample of the dried material (CVM-I) is sent for "HPLC analysis."
HPLC Purity Specification: Not Less than 90.0 % (Area) (mixture of Cis and Trans)
Note: After meeting the above specifications, the next steps are initiated (Stage-II).
5
Example 2
Stage-II: Preparation of Racemic Cevimeline Hydrochloride Hemihydrate
(CVM-II).
In the RBF (4-neck, round bottom flask), isopropyl alcohol (1950 ml) is charged.
10 Thioacetic acid salt of 3-hydroxy-3-acetoxymercapto methyl quinuclidine (CVMI) (200.0 gm) is added followed by the addition of 20-25% IPA. HCL (455.0 gm)
and flushed with isopropyl alcohol (50 ml).
The reaction mass is heated to a temperature of 75 to 85°C and maintained in this
range for 3 to 3.5 hours. Then the reaction mass is cooled to 25 to 35°C.
15 Acetaldehyde diethyl acetal (405.47 gm) is slowly introduced. The reaction mass is
heated again to 75 to 85°C and stirred for 3 to 4 hours in this temperature range.
The completion of reaction is confirmed by HPLC analysis with following limit.
Determination of 3-hydroxy-3 acetoxymercapto methyl quinuclidine (CVM-I) to
ensure completion of the reaction
20 Content of 3-hydroxy-3 acetoxymercapto methyl quinuclidine (CVM-I) is
determined (by HPLC % area) with a limit of not more than 10.0 %, preferably not
more than 5.0 % and most preferably not more than 3.0 %.
Note: If the result is compliant, the next steps in the process are initiated.
25 Solvent distillation:
The reaction mass is cooled below 45°C. The isopropyl alcohol is completely
distilled from the reaction mass, using vacuum to ensure the temperature is below
60°C. The reaction mass is degassed for 10 to 15 minutes to remove as much
isopropyl alcohol (IPA) as possible, ensuring the vacuum is not less than (NLT) 650
30 mmHg at 50 to 60°C. After degassing, the reaction mass is cooled to below 40°C.
67
Work up:
Dichloromethane (2000 ml) is charged into the RBF, ensuring the temperature
below 40°C. The reaction mass is cooled to 0 to 5°C. The appropriate amount of
5 the 25% sodium hydroxide solution (approx. 2000 ml) is gradually added in RBF
at a temperature of 0 to 15°C, aiming to adjust the pH above 11.5.
Layer separation:
10 Purified water (1000 ml) is charged into the RBF, Then the temperature is raised
between 25 and 35°C. the mixture is stirred for 15 to 30 minutes within this
temperature range. The mixture is allowed to settle for 15 to 30 minutes. Afterward,
the organic layer is kept in a separate RBF.
Dichloromethane (400 ml) is added to the aqueous layer, the combination is stirred
15 for 15 to 30 minutes at the same temperature. Then, it is allowed to settle for another
15 to 30 minutes.
Both collected organic layers are combined at 25-35°C. The prepared 5.0% sulfuric
acid solution (1400 ml) is slowly added through the addition funnel to the reaction,
maintaining a temperature of 25 to 35°C. The reaction mass is stirred for 15 to 30
20 minutes within this temperature range. The mixture is allowed to settle for another
15 to 30 minutes. Afterwards, the bottom organic layer is separated.
The organic layer is charged into RBF. The prepared 5.0% sulfuric acid aqueous
solution (600 ml) is introduced slowly through the addition funnel in the organic
layer, keeping the temperature between 25 to 35°C. The reaction mass is stirred for
25 15 to 30 minutes at this temperature range. The mixture is allowed to settle for
another 15 to 30 minutes. Afterward, the bottom organic layer is separated and
discarded.
For the aqueous layers, dichloromethane (400 ml) is charged. The reaction mass is
stirred for 15 to 30 minutes within this temperature range and allowed to settle for
68
another 15 to 30 minutes. Then, the bottom organic layer is separated and discarded.
The aqueous layer reaction mass is cooled to 0 to 5°C.
At a temperature of 0 to 15°C, the 25% sodium hydroxide solution (328 ml) is
slowly added to adjust the pH greater than 11.5.
5 Then the temperature is raised to 25 to 35°C and the reaction mass is maintained
for 15 to 30 minutes within this range. Toluene (1400 ml) is charged in RBF. Stirring
is continued for an additional 15 to 30 minutes at the same temperature. After this,
the mixture is allowed to settle for another 15 to 30 minutes. Once settled, the
bottom aqueous layer is separated. The organic layer is transferred to a separate
10 RBF.
To this aqueous layer, toluene (600 ml) is charged and the temperature between 25
to 35°C is maintained. The mixture is stirred for 15 to 30 minutes within this
temperature range, then it was allowed to settle for another 15 to 30 minutes. After
settling, the bottom aqueous layer is separated and discarded. The organic layer is
15 transferred to separate RBF.
Solvent distillation:
Combine both toluene layers and the maximum possible amount of toluene is
distilled out from the reaction mass using vacuum, ensuring that the temperature
20 remains below 60°C. . The reaction mass is degassed for 15 to 30 minutes at a
temperature between 50 to 60°C, ensuring that the vacuum is no less than 650
mmHg.
The isopropyl alcohol (100 ml) is charged while maintaining the temperature at 50
to 60°C. After this, the reaction mass is cooled to a temperature range of 25 to 35°C.
25
Hydrochlorination:
20-25% IPA.HCl (125.20 gm) is slowly added at 25 to 45°C to the above reaction
mass and it is maintained at 25 to 45°C for 15 to 30 min.
Solvent distillation:
69
The maximum possible amount of toluene and isopropyl alcohol together from the
reaction mass is distilled using vacuum ensuring that the temperature remains below
60°C. . The reaction mass is degassed for 15 to 30 minutes at a temperature between
50 to 60°C, ensuring the vacuum is no less than 650 mmHg.
5
Product isolation:
Cyclohexane (1600 ml) is charged at 50 to 60°C. The reaction mass is cooled to 25
to 35°C. The reaction mass is maintained at 25 to 35°C for 90 to 120 min.
10
Product Filtration & Washing:
The product is filtered and washed with Cyclohexane (400 ml) and the material is
unloaded.
Drying:
15 Wet cake is charged in dryer and dried under vacuum NLT 650 mmHg for an initial
4 hours at 50°C to 60°C. Ensure Water content by KF is not more than 4.6 % after
drying.
After complying with water content and completion of drying, unload the material.
CVM-II is obtained in the range of 0.55-0.80w/w (65.47-95.23%) based on CVM20 I input.
Analyse the dry sample for “Purity by HPLC”. It should be Sum of Cis and trans
isomer of Cevimeline HCl, not Less than 90.0 % (Area)
Example 3
25 Stage-III: Preparation of Cis Cevimeline Para nitro benzoic acid salt (CVMIII)
In the 4-neck round bottom flask charge dichloromethane (1900 ml) and Racemic
Cevimeline Hydrochloride Hemihydrate (CVM-II) (200.0 gm) are charged at
temperatures below 35°C. The mixture is flushed with dichloromethane (50 ml) and
30 the reaction mass is maintained at temperatures below 35°C for 15 to 30 minutes.
70
In the next step, the reaction mass is cooled to a temperature range of -5 to -10°C.
20-25% IPA.HCl (60 ml) is added at this temperature. Gradually stannic chloride
(319.20 gm) is added while maintaining the temperature between -5 to -10°C, and
then flushed with an additional dichloromethane (50 ml). The reaction mass
5 temperature is raised to 25 to 35°C and stirred within this temperature range for up
to 24 hours.
Determination of Trans isomers of cevimeline content by HPLC - Trans isomers
should not be more than 5.0%.
10
71
Work up:
Purified water (2000 ml) is charged below 35°C in RBF. The purified water is
chilled to 5-8°C. The reaction mass in transferred to chilled purified water in the
RBF, maintaining a temperature of 5-8°C. Then the reaction mass is maintained at
5 0 to 5°C for 15 to 30 minutes.
An appropriate amount of the 25% Sodium Hydroxide solution (2000 ml) is slowly
added through the addition funnel in RBF, maintaining a temperature of 0 to 15°C
to adjust the pH above 11.5
10 Layer separation:
Temperature of the reaction mass is increased between 25 and 35°C. The mass is
stirred for 15 to 30 minutes, ensuring the temperature remains below 35°C. It is
allowed to settle for another 15 to 30 minutes within the same temperature range.
Then, the bottom organic layer is separated and kept in separate RBF. Next,
15 Dichloromethane is added (400 ml) to the RBF containing aqueous layer ensuring
the temperature remains below 35°C. The solution is stirred for 15 to 30 minutes at
a temperature below 35°C. It is allowed to settle for the same duration. The bottom
organic layer is separated and kept in separate RBF, once more and the aqueous
layer is discarded.
20 The 5.0% sulfuric acid aqueous solution (1400 ml) is added to the RBF via the
addition funnel, maintaining a temperature of 25 to 35°C. The mixture is stirred for
15 to 30 minutes within this temperature range. Then the mixture is allowed to settle
for another 15 to 30 minutes. Finally, the layers are separated. The aqueous layer is
kept in a separate RBF.
25
The Organic Layer is charged in RBF at 25-35°C. 5% Sulfuric acid aqueous
solution (600 ml) is added slowly at 25 to 35°C through an addition funnel in the
reactor. It is stirred for 15 to 30 minutes. It is allowed to settle for 15 to 30 minutes.
The bottom Organic layer is separated from the aqueous layer and the organic layer
30 is discarded.
72
Dichloromethane (400 ml) is charged into the combined aqueous layers at 25 to
35°C and stirred for 15 to 30 minutes. It is allowed to settle for 15 to 30 minutes.
The bottom organic layer is separated from the aqueous layer and the organic layer
5 is discarded. The aqueous reaction mass is cooled to 0 to 5°C.
25% Sodium Hydroxide solution (375 ml) is slowly added in sufficient amount
through the addition funnel in RBF at 0 to 15°C to adjust pH above 11.5.
10 Layer separation:
The above reaction mass is heated to 25-35°C and stirred for 15-30 minutes.
Toluene (1400 ml) is added while maintaining the temperature between 25 to 35°C
and stirred for an additional 15-30 minutes. The mixture is allowed to settle for 15-
30 minutes within the same temperature range. The bottom aqueous layer is
15 separated and retained. Toluene layer is stored separately.
The temperature of the retained aqueous layer is maintained between 25-35°C.
Then toluene (600 ml) is added ensuring the temperature remains between 25 to
35°C, and stirred for 15-30 minutes. After stirring, the mixture is allowed to settle
for 15-30 minutes at 25-35°C.. Separate toluene and aqueous layers. Toluene layer
20 is stored aqueous layer is discarded.
Solvent Distillation:
Combine the toluene layers and the reaction mass is heated to distilled out toluene
under a vacuum, maintaining a temperature below 60°C. The reaction mass is
25 degassed for 15-30 minutes at 50-60°C, ensuring a vacuum of no less than 650
mmHg. The degassed reaction mass is cooled to 32-38°C. The cevimeline base is
stored in RBF.
Cis Cevimeline base solution preparation:
30 Acetone (310 ml) is charged in RBF containing Cis Cevimeline Base (155 gm
obtained above) and stirred until a clear solution is observed.
73
Product isolation:
Acetone (400 ml) followed by para nitro benzoic acid (122 gm) are charged in the
RBF at below 350C. Slowly Cis Cevimeline Base Solution is added at below 55°C
5 through an addition funnel into the reaction mass. The addition funnel is flushed
with Acetone (65 ml) and charged in the RBF below 55°C. The reaction mass is
heated to reflux at 50 to 60°C and maintained for 45 to 60 min at 50 to 60°C. It is
slowly cooled to 25 to 35°C and chilled to 0 to 5°C maintaining at 0 to 5°C for 120
to 180 minutes.
10
Product Filtration & Washing:
The product is filtered through the Buchner funnel and washed with chilled Acetone
(155 ml). The crude Cis cevimeline para nitrobenzoic acid salt is unloaded.
LOD of Cis cevimeline para nitrobenzoic acid salt is checked before purification
15 (for dry weight calculation) and the dry weight based on LOD is calculated.
Purification
Purified water (850 ml) is charged in RBF followed by crude Cis Cevimeline para
nitrobenzoic acid salt (on a dry basis) (225.0 gm) below 35°C and flushed with
20 purified water (50 ml) and heating to 70-80°C and stirring for 30 to 60 minutes to
get a clear solution. The solution is slowly cooled to 25 to 35°C. and slowly chilled
to 5 to 10°C and maintained for 120 to 180 minutes.
Product Filtration & Washing:
25 The product is filtered through the Buchner funnel and washed with chilled Purified
water (225 ml). The Cis cevimeline para nitrobenzoic acid salt is unloaded. The
purification process is repeated in water till impurities are controlled as provided in
table 16 below
30
74
Table 16
Tests Specifications
Organic impurities by HPLC <621>
Trans Cevimeline impurity Not more than 0.30 %
Diol impurity Not more than 0.1 %
Thiol impurity Not more than 0.1 %
Cevimeline sulfoxide (RRR) Not more than 0.15 %
Cevimeline sulfoxide (RRS) Not more than 0.15 %
Cevimeline N-Oxide Not more than 0.15 %
Cevimeline impurity-1: 3-(((1-((((1r,4r)-3- Not more than 0.15 %
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio)
methyl) quinuclidin-3-ol.
Cevimeline impurity-2: 3-(((1-((((1s,4s)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio)
methyl) quinuclidin-3-ol.
Not more than 0.15 %
Single largest unspecified impurity Not more than 0.1 %
Total impurities
(Total impurity of Method II + Trans isomer)
Not more than 1 %
Drying:
The drying of the material is carried out under vacuum at NLT 650 mmHg at 45°C
5 to 55°C for an initial 4 hours till water content by KF is not more than 3.0%. Yield
is obtained in the range of 120-220 gm, 40.08-73.48% molar.
75
Example 4
Stage-IV: Preparation of Cevimeline Hydrochloride (A-012)
Purified water (500 ml) and Cis Cevimeline para nitro benzoic salt (175) are
5 charged in the 4-neck round bottom flask (RBF) and flushed with purified water
(25 ml) at below 35°C and the mass is cooled to 10°C to 20°C. Slowly, 25% Sodium
Hydroxide solution is added through the addition funnel in RBF to adjust pH above
11.5.
10 Product extraction and layer separation:
The temperature is raised and maintained at 25-35°C for 30 to 45 minutes.
Cyclohexane (1400 ml) is charged in the RBF and stirred for 30 to 45 minutes and
allowed to settle for 15 to 30 minutes and then the layers are separated.
15 The aqueous layer is charged in the RBF. Cyclohexane (350 ml) is added. Then it
is stirred for 30-45 minutes. Further it to allowed to settle for 15 to 30 minutes. The
layers are separated and the bottom aqueous layer is collected and discarded.
Both organic layers are combined at 25-35°C. Purified water (87 ml) is charged and
20 stirred for 30-45 minutes and allowed to settle for 15 to 30 minutes. The bottom
aqueous layer is separated and discarded.
Carbon treatment:
Both organic layers are charged at 25-35°C in a RBF, Further, activated charcoal
25 (8.75 gm) is charged and maintained for 45 to 60 min.
Carbon Filtration & washing:
The charcoal is filtered through celite bed and washed with cyclohexane (175 ml).
The filtrate is collected in a RBF.
30
76
Hydrochlorination:
The reaction mass is chilled to 5 to 10°C and slowly IPA (85.4 gm) and 20-
25%IPA.HCl (85.4 gm) (net basis 0.98 mole equivalent) are added and maintained
for 90 to 120 min.
5
Product Filtration & Washing:
The product is filtered through the Buchner funnel and washed with cyclohexane
(350 ml). The wet cake of Cis cevimeline hydrochloride is unloaded. The wet cake
is charged in the dryer and the material is dried under vacuum with NLT 650 mmHg
10 at 50°C to 60°C for 2.0 hours. The dry material is unloaded for the crystallisation
process. Yield is obtained in the range of 43.75-105.0 gm, 0.25-0.60 w/w (37.42-
89.82%) on CVM-III input.
Crystallisation to get the desired particle size:
15 Isopropyl alcohol (175 ml) and the previously dried Cevimeline hydrochloride (50
gm) are charged in the 4-neck round bottom flask (RBF) at temperatures below
35°C and flushed with isopropyl alcohol (25 ml) and subjected to stirring. The
reaction mass is heated to 60°C to 65°C. Once a clear solution is observed, stirring
speed is slowed down and slowly cyclohexane (500 ml) is added while maintaining
20 the temperature at 60°C to 65°C. The mixture is gradually cooled to 25°C to 35°C
and then further chilled to 0°C to 5°C and maintained for 90 to 120 minutes.
Product Filtration & Washing:
The product is filtered and washed with cyclohexane (25 ml). The wet cake of Cis
25 cevimeline hydrochloride is unloaded.
Drying:
Wet cake is charged in to dryer and Vacuum drying of the material is done at 50°C
to 60°C for 4 Hours then till Water content by KF is achieved Between 3.50 – 4.50.
Unload the material and yield is measured. It is obtained in the range of 0.88-0.96
30 w/w (88.0-96.0% molar) based on input Cevimeline hydrochloride.
77
Sifting:
The dried material is sifted using the desired mesh sieve in Sifter and sifted material
is collected.
The samples are taken for analysis and are analysed for
5 i) Description;
ii) Organic impurities by HPLC.; and
ii) Particle Size Distribution analysis
and comply with the specification of table 17.
10 Table 17
Tests Specifications
i. Description As per USP
ii. Organic impurities by HPLC <621>
Trans Cevimeline impurity Not more than 0.30 %
Diol impurity As per ICH guideline
Thiol impurity
Cevimeline sulfoxide (RRR)
Cevimeline sulfoxide (RRS)
Cevimeline N-Oxide
Cevimeline impurity-1: 3-(((1-((((1r,4r)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio)
methyl) quinuclidin-3-ol.
Cevimeline impurity-2 : 3-(((1-((((1s,4s)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio)
methyl) quinuclidin-3-ol.
Single largest unspecified impurity
Total impurities
(Total impurity of Method II + Trans isomer)
Not more than 1.00 %
Additional controlled impurities by HPLC
2-Nitro Benzoic Acid
78
2,4 Dinitro Benzoic Acid As per ICH M7
4-Nitro Benzoic Acid guideline
3-Nitro Benzoic Acid
3,4 Dinitro Benzoic Acid
4-Niro Toluene
The sum of all genotoxic impurities
Benzene content
Particle size distribution (PSD)
d10 Not more than 20 µm
d50 Not more than 50 µm
d90 Not more than 100 µm
Alternatively, by employing isopropyl alcohol slurry, the following particle size
distribution can be achieved.
Additionally, if a lower particle size distribution is desired, isopropyl alcohol slurry
5 can be used which provides the following particle size distribution (table 18).
Table 18
d10 Not more than 5 µm; preferably Between 1.0 and 5 µm
d50 Not more than 10 µm, preferably Between 1.0 and 10.0 µm.
d90
Not more than 25 µm, preferably not more than 20 µm, most
preferably not more than15.0 µm.
Over all yield is obtained in the range of 43.75-105.0 gm, 0.25-0.60 w/w (37.42-
89.82%) on CVM-III input.
79
Claims
We claim
1. A process for preparing Cis Cevimeline Hydrochloride comprising
5 i) Isomerization of racemic Cevimeline hydrochloride hemihydrate
using a metal catalyst to produce in situ Cis-Cevimeline base;
ii) Reacting in a solvent Cis-Cevimeline base in situ with an organic
acid to produce organic acid salt of Cis cevimeline and optionally
recrystallizing the same;
10 iii) Salt breaking by treating the organic acid salt of Cis cevimeline of
step ii with a base;
iv) Adding cyclohexane in the reaction mixture of step iii and
extracting;
v) Optionally repeating extraction with cyclohexane;
15 vi) Treating cyclohexane solution with charcoal;
vii) Filtering and cooling the filtrate to 5 – 10°C;
viii) Adding isopropyl alcohol and isopropyl alcohol hydrochloride at 5-
10°C to filtrate/reaction mass of step vii and maintaining at the same
temperature for 30 – 300 minutes, preferably from 90-120 mins to
20 produce Cis cevimeline hydrochloride;
ix) Filtering and subjecting wet cake of Cis cevimeline hydrochloride
to drying;
x) Optionally treating dried Cis cevimeline hydrochloride with a
solvent and drying.
25 2. The process as claimed in claim 1 wherein the metal catalyst is stannic
chloride.
3. The organic acid is p-nitro benzoic acid.
4. The process as claimed in claim 1 wherein in the salt breaking step, the base
for treating organic acid salt of Cis cevimeline is a solution of sodium
80
hydroxide and the amount of sodium hydroxide solution added provides a
pH in the range of 11.5 -13.5.
5. The process as claimed in claim 1 wherein
a) Cis-Cevimeline base prepared in situ contains not more than 5 % of trans
5 isomer;
b) The organic acid is p-nitro benzoic acid and organic acid salt is p-nitro
benzoic acid salt of Cis Cevimeline.
c) The solvent for reacting Cis-Cevimeline base with p-nitro benzoic acid
is acetone; and
10 d) p-nitro benzoic acid salt of Cis Cevimeline is recrystallized in water by
dissolving it in water at 70-80°C to obtain a clear solution followed by
cooling and isolation.
6. The process as claimed in claim 1 treating dried Cis cevimeline
hydrochloride with a
15 solvent comprises either slurring the dried Cis cevimeline hydrochloride in
isopropyl alcohol or recrystallizing Cis cevimeline hydrochloride in
isopropyl alcohol and
cyclohexane wherein Cis cevimeline hydrochloride is first dissolved in
isopropyl alcohol and precipitated using cyclohexane.
20 7. The process as claimed in claim 6 wherein dried Cis cevimeline
hydrochloride is slurry in isopropyl alcohol.
8. The process as claimed in claim 7 wherein the ratio of amounts of Cis
cevimeline hydrochloride and isopropyl alcohol is from 1:2 to 1:5 wherein
Cis cevimeline hydrochloride amount is expressed in weight and amounts
25 of isopropyl alcohol is expressed in volume.
9. The process as claimed in claim 6 wherein dried Cis cevimeline
hydrochloride is dissolved in isopropyl alcohol and precipitated using
cyclohexane.
81
10. The process as claimed in claim 9 wherein the ratio of amounts of Cis
cevimeline hydrochloride, isopropyl alcohol and cyclohexane is from
1:4:10 to 1:4:20 wherein Cis cevimeline hydrochloride amount is expressed
in weight and amounts of isopropyl alcohol and cyclohexane are expressed
5 in volume.
11. The process as claimed in claim 7 wherein Cis cevimeline hydrochloride
after slurring in isopropyl alcohol has the following particle size
distribution,
D10: not more than 5µm;
10 D50: not more than 10µm;
D90: not more than 25 µm, preferably not more than 20 µm, most preferably
not more than 15 µm.
12. The process as claimed in claim 9 wherein Cis cevimeline hydrochloride
after dissolving in isopropyl alcohol and precipitating by cyclohexane has
15 the following particle size distribution,
D10: not more than 20µm, preferably not more than 10 µm and more
preferably not more than 7.5 µm;
D50: not more than 50µm; preferably not more than 30 µm and more
preferably between 10 µm - 25 µm;
20 D90: not more than 100 µm, preferably not more than 80 µm, most
preferably not more than 75 µm.
13. The process as claimed in claim 1 wherein the Cis cevimeline hydrochloride
after the solvent treatment is dried till water content is from 3.5 - 4.5 %.
14. The process for preparing Cis Cevimeline Hydrochloride as claimed in
25 claim 5 and 6 wherein the Cis cevimeline hydrochloride contains
i) not more than 0.5 %, preferably not more than 0.3 % of Trans isomer.
ii) Not more than 0.1 % of single unspecified impurity;
iii) Not more than 0.15 % of single specified impurity selected from
a) Cevimeline sulfoxide (RRR);
30 b) Cevimeline sulfoxide (RRS);
82
c) Cevimeline N-Oxide;
d) Cevimeline impurity-1: 3-(((1-((((1R,4R)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl)
quinuclidin-3-ol;
5 e) Cevimeline impurity-2: 3-(((1-((((1S,4S)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl)
quinuclidin-3-ol;
iv) Not more than 0.1 % of diol impurity;
v) Not more than 0.1 % of thiol impurity.
10 15. The process for preparing Cis Cevimeline Hydrochloride as claimed in
claims 5, 6, and 14 wherein the Cis cevimeline hydrochloride contains not
more than 0.15 % of acid degradant impurity selected from
a) Cevimeline impurity-1: 3-(((1-((((1R,4R)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol;
15 b) Cevimeline impurity-2: 3-(((1-((((1S,4S)-3-Hydroxyquinuclidin-3-yl)
methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.
16. The process as claimed in claim 1 wherein Cevimeline hydrochloride
hemihydrate (CVM-II) is prepared by reacting racemic cevimeline base
prepared in situ and isopropyl hydrochloride in isopropyl alcohol and
20 followed by isolation/crystallization using cyclohexane.
17. The process as claimed in claim 16 wherein racemic cevimeline base is
obtained in a two steps reaction wherein in the first step, thioacetic acid salt
of 3-hydroxy-3-acetoxymercapto methyl quinuclidine (CVM-I) is reacted
with isopropyl alcohol hydrochloride in isopropyl alcohol at 75 – 85°C to
25 produce in situ 3-hydroxy-3-mercaptomethyl quiniclidine which is reacted
with acetaldehyde diethyl acetal followed by one or more work up
processes.
18. The process as claimed in claim 17 wherein thioacetic acid salt of 3-
hydroxy-3-acetoxymercapto methyl quinuclidine (CVM-I) is reacted with
83
isopropyl alcohol hydrochloride in isopropyl alcohol in a mole ratio of from
1:3 – 1: 4. at a temperature of from 75-85°C.
19. The process as claimed in claim 18 wherein thioacetic acid salt of 3-
hydroxy-3-acetoxymercapto methyl quinuclidine is obtained from 3-
5 Quinuclidinone hydrochloride in two steps wherein in a first step 3-
Quinuclidinone hydrochloride in a first solvent is reacted with Trimethyl
sulfoxonium iodide at 0-10°C in presence of a base to produce in situ an
intermediate epoxide of 3-methylene quinuclidine and in the subsequent
step, epoxide of 3-methylene quinuclidine in situ is reacted with Thioacetic
10 acid in a second solvent environment, yielding the Thioacetic Acid Salt of
3-hydroxy-3-acetoxymercaptomethyl quinuclidine.
20. The process as claimed in claim 19 wherein the first solvent is selected from
dimethyl sulfoxide, dimethyl formamide, tetrahydrofuran; a combination of
dimethyl sulfoxide and dimethyl formamide; and a second solvent is
15 selected from cyclohexane, Di-isopropyl ether, ethyl acetate and toluene.
21. The process as claimed in claim 19 wherein the base is selected from sodium
hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide,
sodium hydride, potassium hydride, sodium tertiary butoxide, potassium
tertiary butoxide and any combination thereof.
20 22. The process as claimed in claim 19 wherein the base is added in 2 - 6
portions.
23. The process as claimed in claim 21 wherein the base is potassium tertiary
butoxide.
24. The process as claimed in claim 23 wherein the base is potassium tertiary
25 butoxide and it is added in five equal portions/lots / parts at 0-10°C.
25. Cis Cevimeline Hydrochloride containing not more than 0.15 % of a single
specified impurity selected from
i) Cevimeline impurity-1: 3-(((1-((((1R,4R)-3-Hydroxyquinuclidin-3-
yl) methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol; and
84
ii) Cevimeline impurity-2: 3-(((1-((((1S,4S)-3-Hydroxyquinuclidin-3-
yl) methyl) thio) ethyl) thio) methyl) quinuclidin-3-ol.
26. Cis Cevimeline Hydrochloride containing
i) not more than 0.5 %, preferably not more than 0.3 % of Trans isomer;
5 ii) Not more than 0.1 % of single unspecified impurity;
iii) Not more than 0.15 % of single specified impurity selected from
a) Cevimeline sulfoxide (RRR);
b) Cevimeline sulfoxide (RRS);
c) Cevimeline N-Oxide;
10 d) Cevimeline impurity-1: 3-(((1-((((1R,4R)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl)
quinuclidin-3-ol; and
e) Cevimeline impurity-2: 3-(((1-((((1S,4S)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl)
15 quinuclidin-3-ol.
iv) Not more than 0.1 % of diol impurity;
v) Not more than 0.1 % of thiol impurity.
27. Cis cevimeline para nitrobenzoic acid salt having following specification
Tests Specifications
Organic impurities by HPLC <621>
Trans Cevimeline impurity Not more than 0.30 %
Diol impurity Not more than 0.1 %
Thiol impurity Not more than 0.1 %
Cevimeline sulfoxide (RRR) Not more than 0.15 %
Cevimeline sulfoxide (RRS) Not more than 0.15 %
Cevimeline N-Oxide Not more than 0.15 %
85
Cevimeline impurity-1: 3-(((1-((((1r,4r)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl)
thio) methyl) quinuclidin-3-ol.
Not more than 0.15 %
Cevimeline impurity-2: 3-(((1-((((1s,4s)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl)
thio) methyl) quinuclidin-3-ol.
Not more than 0.15 %
Single largest unspecified impurity Not more than 0.1 %
Total impurities
(Total impurity of Method II + Trans isomer)
Not more than 1 %
28. Mixture of i) Cevimeline impurity-1 which is 3-(((1-((((1R,4R)-3-
Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl) quinuclidin-3-
ol and ii) Cevimeline impurity-2 which is 3-(((1-((((1S,4S)-3-
5 Hydroxyquinuclidin-3-yl) methyl) thio) ethyl) thio) methyl) quinuclidin-3-
ol.
29. Mixture of claim 27 wherein the said mixture has a purity of at least 75 %,
preferably at least 80 %, more preferably at least 85 % and most preferably
at least 90 % considering a total of two impurities.
10 30. Mixture of claim 27 or 28 wherein weight ratio of Cevimeline impurity-1
and Cevimeline impurity-2 is from 1:20 to 20:1, preferably from 1:10 to
10:1, more preferably from 1:7.5 to 7.5:1, and most preferably from 1:5 to
5:1.
31. Cis cevimeline hydrochloride with the following particle size distribution,
15 D10: not more than 5µm;
D50: not more than 10µm;
D90: not more than 25 µm, preferably not more than 20 µm, most preferably
not more than 15 µm;
wherein Cis cevimeline hydrochloride is slurried in isopropyl alcohol and dried before particle size measurement.
32. Cis cevimeline hydrochloride with the following particle size distribution,
D10: not more than 20µm, preferably not more than 10 µm and more
preferably not more than 7.5 µm;
D50: not more than 50µm; preferably not more than 30 µm and more
5 preferably between 10 µm - 25 µm;
D90: not more than 100 µm, preferably not more than 80 µm, most
preferably not more than 75 µm.
wherein Cis cevimeline hydrochloride is dissolved in isopropyl alcohol and
precipitated by cyclohexane and dried before particle size measurement.