CRYSTALLIZATION PROCESS OF TRICYCLIC INDOLE DERIVATIVES
Technical Field of the Invention
The present invention relates to a composition comprising a tricyclic indole compound.
More specifically the present invention relates to wherein said composition has a more
favourable impurity profile as compared with known compositions comprising said
compound.
Description of Related Art
Tricyclic indole compounds are known in the art and have been reported to have
application variously as melatonin antagonists (Davies 1998 J Med Chem; 4 1: 451-467),
secretory phospho lipase A2 inhibitors (Anderson et al EP 0952149 Al), treatment for
Alzheimer's disease (Wantanabe WO 99/25340), treatment of inflammatory diseases
such as septic shock (Kinnick et al WO 03/014082 and WO 03/016277) and binders of
high affinity to translocator protein (TSPO, formerly known as peripheral
benzodiazepine receptor; Wadsworth et al (WO 2010/109007).
The synthesis of these tricyclic indole compounds comprises a condensation reaction
between an analine and a bromo oxocycloalkanecarboxylate, followed by cyclization in
the presence of a zinc halide. One problem with this cyclization reaction is that more
than one cyclized isomer can result, as illustrated in Scheme 1 below:
The incorrect isomer is formed when the R group reacts with the -OH. This incorrect
isomer has similar reactivity to the correct isomer and as a consequence when any
further steps are taken to modify the correct isomer, a respective incorrect isomer is
generated in the reaction mixture. This is particularly problematic if the resultant
compound is intended for in vivo use, as the incorrect isomer will likely compete with
the correct isomer for binding to the intended biological target.
In the method described by Kinnick et al (WO 03/014082), a chloro group was
introduced at the R position illustrated in Scheme 1 with the aim of forcing the
cyclization reaction to take place in just one way and result in only the correct cyclized
isomer. This strategy was applied by Wadsworth et al (WO 2010/109007) in the
cyclization reaction illustrated in Scheme 2 below (where Et = ethyl and Bz = benzyl):
Work up and chromatographic purification of the resultant reaction mixture was
followed by removal of the chloro group and conversion of the ethyl to diethyl amine to
obtain a key intermediate, which in turn was purified using crystallization from diethyl
ether. Purity of the key intermediate was still only 71%. When investigating this
particular reaction, the present inventors have found that the purified reaction mixture
still contains an amount of the incorrect isomer, which is evidently difficult to remove.
There is therefore a need for a method to obtain these and similar tricyclic indole
compounds where the amount of incorrect isomer is reduced or preferably eliminated.
Summary of the Invention
The present invention relates to a composition comprising a tricyclic indole compound
wherein the quantity of an incorrect isomer in said composition is reduced. The
composition therefore has a higher purity and better impurity profile than known
compositions comprising said tricyclic indole compound and as a consequence has
superior properties, particularly when said compound is destined for use in vivo as a
therapeutic or diagnostic agent. Also provided by the present invention is a method to
make the composition of the invention, a pharmaceutical composition comprising the
composition of the invention, and use of the composition of the invention in a medical
method.
Detailed Description of the Preferred Embodiments
In one aspect, the present invention provides a composition comprising a compound of
Formula I :
wherein:
hydrogen, Ci_3 alkyl, Ci_3 alkoxy, or halo;
R2 is hydroxyl, halo, cyano, Ci_3 alkyl, Ci_3 alkoxy, Ci_3 fluoroalkyl, or Ci_3 fluoroalkoxy;
3 7 R is -N-R R8 wherein R7 and R8 are hydrogen, Ci_6 alkyl, C7- io arylalkyl or, together
with R7, forms a nitrogen-containing C4 6 aliphatic ring;
R4 is O, S, SO, S0 2 or CH2;
R5 is CH2, CH2-CH2, CH(CH 3)-CH 2 or CH2-CH 2-CH 2;
R6 is -A^R 9 wherein A1 is a bond or Ci_i0 alkylene, and R9 is hydrogen, fluoro or a
leaving group, or R9 is the group -O-R 1 wherein R1 is hydrogen, Ci_3 alkyl, C3-6 aryl,
C7-10 arylalkyl, or a hydroxyl protecting group;
wherein said composition comprises no more than 1% of a compound of Formula II:
wherein R2 to R6 are as defined for Formula I .
The term "alkyl" used either alone or as part of another group is defined as any straight
- CnH2n+i group, branched - CnH2n+i group wherein n is >3, or cyclic - CnH2 _i group
where n is >2. Non- limiting examples of alkyl groups include methyl, ethyl, propyl,
isobutyl, cyclopropyl and cyclobutyl.
The term "alkoxy" refers to an alkyl group as defined above comprising an ether linkage,
and the term "ether linkage" refers to the group -C-0-C-. Non-limiting examples of
alkoxy groups include, methoxy, ethoxy, and propoxy.
The term "halo" or "halogen" is taken to mean any one of chloro, fluoro, bromo or iodo.
The term "hydroxyl" refers to the group -OH.
The term "cyano" refers to the group -CN.
The terms "fluoroalkyl" and ''fluoroalkoxy ''refer respectively to an alkyl group and an
alkoxy group as defined above wherein a hydrogen is replaced with a fluoro.
The term "arylal y refers to an aryl-substituted alkylene group wherein "aryl" refers to
any molecular fragment or group which is derived from a monocyclic or polycyclic
aromatic hydrocarbon, or a monocyclic or polycyclic heteroaromatic hydrocarbon and
"alkylene" refers to a divalent linear -CnH2n- group.
A "nitrogen-containing C aliphatic ring " is a saturated C4 6 alkyl ring comprising a
nitrogen heteroatom. Examples include pyrolidinyl, piperidinyl and morpholinyl rings.
The term "leaving group" refers to a molecular fragment that departs with a pair of
electrons in heterolytic bond cleavage. Non-limiting examples of suitable leaving groups
include halo groups selected from chloro, iodo, or bromo, aryl or alkyl sulfonates such
as tosylate, triflate, nosylate or mesylate.
The term "protecting group " is meant a group which inhibits or suppresses undesirable
chemical reactions, but which is designed to be sufficiently reactive that it may be
cleaved from the functional group in question to obtain the desired product under mild
enough conditions that do not modify the rest of the molecule. Protecting groups are
well-known in the art and are discussed in detail in 'Protective Groups in Organic
Synthesis', by Greene and Wuts (Fourth Edition, John Wiley & Sons, 2007). Nonlimiting
examples of suitable protecting groups for hydroxyl include acetyl (-COCH ),
benzoyl (-COC 6H ), benzyl (-CH 2C6H ), b-methoxyethoxymethyl ether (MEM),
dimethoxytrityl (DMT) and methoxymethyl ether (MOM).
In a first preferred embodiment R1 is halo and in a second preferred embodiment R1 is
hydrogen. When R1 is halo it is most preferably chloro or bromo, and especially
preferably chloro.
In a preferred embodiment R2 is halo, C1-3 alkoxy or C1-3 fluoroalkoxy, most preferably
hydrogen, halo or Ci_3 alkoxy, especially preferably hydrogen, fluoro or methoxy, and
most especially preferably methoxy.
3 7 In a preferred embodiment, R is -N-R R8 wherein R7 and R8 are Ci_6 alkyl or C7-10
arylalkyl, most preferably wherein R7 and R8 are C1-3 alkyl, especially preferably wherein
R and R8 are both ethyl.
In a preferred embodiment R4 is CH 2 .
In a preferred embodiment, R5 is CH 2-CH 2 .
In a first preferred embodiment, R6 is-A^R 9 wherein A 1 is Ci_io alkylene, most
preferably C1-3 alkylene and especially preferably ethylene, and R9 is the group -O-R 1
wherein R1 is C7-10 arylalkyl or a hydroxyl protecting group, most preferably wherein
R1 is a hydroxyl protecting group.
In a second preferred embodiment R6 is - A R wherein A 1 is Ci_io alkylene, most
preferably Ci_3 alkylene and especially preferably ethylene, and R9 is hydrogen, fluoro or
a leaving group. Where R9 is fluoro it is preferably [1 F]fluoro, such that the
composition of the invention is an "in vivo imaging composition " . Where R9 is a leaving
group the composition of the invention is a "precursor composition " that can be reacted
with [1 F]fluoride to obtain the in vivo imaging composition. The leaving group is
preferably halo, or an aryl or alkyl sulfonate, most preferably an aryl or alkyl sulfonate,
and especially preferably tosylate, triflate, nosylate or mesylate.
The term "no more than " should be understood to mean any amount less than the quoted
percent quantity. Therefore no more than 1% means any amount between 0-1%. In an
ideal embodiment of the composition of the present invention there is 0% of said
compound of Formula II in the composition of the invention. However, in reality, it may
be that at least a trace amount of the compound of Formula II remains in the
composition, i.e. no more than 1% could e.g. refer to 0.1-1%.
In a first preferred composition of the present invention:
R1 is halo, preferably chloro or bromo, and most preferably chloro;
R2 is halo, Ci_3 alkoxy or Ci_3 fluoroalkoxy, preferably hydrogen, halo or Ci_3 alkoxy,
most preferably hydrogen, fluoro or methoxy, and especially preferably methoxy;
3 7 8 R is - N -R'R wherein R7' and R8° are Ci_6 alkyl or C7-10 arylalkyl, preferably wherein R7
and R8 are Ci_3 alkyl, most preferably wherein R7 and R8 are both ethyl;
R4 is CH 2
R5 is CH 2-CH 2; and,
R6 is-A^R 9 wherein A1 is Ci_io alkylene, most preferably C1-3 alkylene and especially
preferably ethylene, and R9 is the group -O-R 1 wherein R1 is C7-10 arylalkyl or a
hydroxyl protecting group, preferably wherein R1 is a hydroxyl protecting group.
In a second preferred composition of the present invention:
R1 is hydrogen;
R2 is halo, Ci_3 alkoxy or Ci_3 fluoroalkoxy, preferably hydrogen, halo or Ci_3 alkoxy,
most preferably hydrogen, fluoro or methoxy, and especially preferably methoxy;
3 7 8 R is - N -R'R wherein R7' and R8° are Ci_6 alkyl or C7-10 arylalkyl, preferably wherein R7
and R8 are C1-3 alkyl, most preferably wherein R7 and R8 are both ethyl;
R4 is CH 2
R6 is -A^R wherein A1 is Ci_io alkylene, most preferably C1-3 alkylene and especially
preferably ethylene, and R9 is hydrogen, fluoro, or a leaving group, preferably wherein
R9 is fluoro or a leaving group, wherein said fluoro is [1 F]fluoro and wherein said
leaving group is preferably halo, or an aryl or alkyl sulfonate, most preferably an aryl or
alkyl sulfonate, and especially preferably tosylate, triflate, nosylate or mesylate. This
second preferred composition can therefore either be an in vivo imaging composition or
a precursor composition of the invention.
The compound of Formula I and the compound of Formula II of the composition of the
present invention as defined above may each comprise a chiral centre. All forms of such
isomer, including enantiomers and diastereoisomers, are encompassed by the present
invention. The compound of Formula I and the compound of Formula II may be present
in the composition of the present invention as racemic mixture or as an enantiomericallyenriched
mixture, or the racemic mixture may be separated using well-known techniques
and an individual enantiomer maybe used alone. Preferably, the composition of the
invention comprises the S-enantiomer of said compound of Formula I and said
compound of Formula II.
In a preferred embodiment, the composition of the present invention comprises no more
than 0.5% of said compound of Formula II, most preferably no more than 0.3%, especially
preferably no more than 0.2%, and most especially preferably no more than 0.1%.
In a particularly preferred composition of the present invention, said compound of
Formula I is a compound of Formula la:
1 2 7 wherein each of R , R , R , R8, R9 and A1 are as variously defined hereinabove
and said compound of Formula II is a compound of Formula Ila:
wherein each of R , R , R , R and A are as variously defined hereinabove.
Preferably for this particularly preferred composition of the invention:
R1 is hydrogen;
R is fluoro or methoxy;
R and R8 are Ci_6 alkyl;
hydrogen, fluoro or a leaving group; and,
A1 is Ci-io alkylene.
Most preferably for this particularly preferred composition of the invention:
R1 is hydrogen;
R is methoxy;
R and R8 are C
R is [ F]fluoro or an aryl or alkyl sulfonate; and,
A1 is Ci-3 alkylene.
Especially preferably for this particularly preferred composition of the invention:
R1 is hydrogen;
R2 is methoxy;
R7 and R8 are methyl or ethyl;
R9 is [1 F]fluoro, tosylate, triflate, nosylate or mesylate; and,
A1 is Ci-3 alkylene.
Most especially preferably for this particularly preferred composition of the invention:
R1 is hydrogen;
R2 is methoxy;
R and R8 are both ethyl;
R9 is [1 F]fluoro or mesylate; and,
A1 is ethylene.
Where an above-defined particularly preferred composition of the invention comprises
1 F it is an in vivo imaging composition, and where it comprises a leaving group, it is a
precursor composition.
In another aspect, the present invention comprises a method to obtain the composition as
defined hereinabove wherein said method comprises crystallization of a reaction mixture
comprising said compound of Formula I as defined hereinabove, and said compound of
Formula II as defined hereinabove, wherein said crystallization is carried out in a suitable
organic solvent in the presence of a catalytic amount of a weak organic base in order to
obtain said composition.
The term "catalytic amount " means an amount of a substance used in a chemical reaction
as a catalyst and is generally much smaller than the stoichiometric amounts of either
reactants or products.
The term "suitable organic solvent " encompasses non-polar solvents and polar aprotic
solvents, suitably having a dielectric constant of between 3.5-8. Examples of suitable
organic solvents for use in the method of the present invention include diethyl ether,
ethyl acetate, tetrahydrofuran (THF) and diisopropylether. Diethyl ether is preferred.
The term "weak organic base" refers to an organic compound which acts as a base.
Organic bases are generally proton acceptors and usually contain nitrogen atoms, which
can easily be protonated. Amines and nitrogen-containing heterocyclic compounds are
organic bases. Non-limiting examples include pyridine, alkyl amines, morpholine,
imidazole, benzimidazole, histidine, phosphazene bases and hydroxides of some organic
cations. In the context of the present invention alkyl amines are preferred, e.g. N,Ndiisopropyl
amine, triethyl amine or diethyl amine.
The present inventors have found that when using the method of the invention a very
good quality product is obtained having optimum yield. Please refer to Example 1
wherein a method to obtain the composition of the present invention is described. It can
be seen that by applying the method of the invention to the purification of a key
intermediate in the synthesis, the amount of incorrect isomer remaining is significantly
less than when the prior art method for purification of this intermediate is used.
Preferably, the reaction mixture for use in the method of the invention is obtained using a
method comprising cyclization of a compound of Formula III:
wherein:
R1 is as suitably and preferably defined hereinabove;
R2 is as suitably and preferably defined hereinabove;
R is as suitably and preferably defined hereinabove;
R4 is as suitably and preferably defined hereinabove;
R5 is as suitably and preferably defined hereinabove; and,
R6 is as suitably and preferably defined hereinabove;
wherein said cyclization is carried out by reaction of said compound of Formula III with
a zinc halide.
It is preferred that said zinc halide is zinc chloride or zinc bromide, most preferably zinc
chloride.
In a particularly preferred embodiment said zinc chloride is added lot-wise. The term
"lot-wise" means introduction of a reagent to a reaction using more than one addition.
In the context of the present invention said more than one addition comprises a first
addition and a second addition wherein said second addition is carried out at least 6
hours after said first addition. Said lot-wise addition preferably further comprises a third
addition wherein said third addition is carried out said second addition.
Cyclization of said compound of Formula III is preferably carried out wherein R1 is
halogen, preferably chloro, and wherein R6 comprises a protecting group. This is to
ensure that the cyclization reaction results in as much of the correct isomer as possible.
The R1 and R6 group can be converted subsequently using methods well-known to the
person skilled in the art to obtain other R1 and R6 groups as defined above.
Compounds of Formula III can be obtained from commercial starting materials using or
adapting methods described in the prior art. Reference is made in this regard to the
teachings of Julia & Lenzi (Bulletin de la Societe de France 1962: 2262-2263), Davies et
al (J Med Chem 1998; 41: 451-467), Kinnick et al (WO 2003/014082 and WO
2003/016277), Anderson et al (EP0952149 Bl) and Wadsworth et al (WO
2010/109007). In each of these publications compounds of Formula III are obtained by
condensation reaction between an analine and a bromo oxocycloalkanecarboxylate as
illustrated in Scheme 3 below:
Scheme 3
In the above scheme R' is an R3 group as defined herein, R" is an R1 and/or an R2 group
as defined herein, R " is an R6 group as defined herein and n' is an integer of 1-3.
In another aspect, the present invention provides a pharmaceutical composition
comprising the composition of the invention together with a biocompatible carrier
suitable for mammalian administration.
The "biocompatible carrier" is a fluid, especially a liquid, in which the composition of the
invention is suspended or dissolved, such that the pharmaceutical composition is
physiologically tolerable, i.e. can be administered to the mammalian body without
toxicity or undue discomfort. The biocompatible carrier is suitably an injectable carrier
liquid such as sterile, pyrogen- free water for injection; an aqueous solution such as saline
(which may advantageously be balanced so that the final product for injection is either
isotonic or not hypotonic); an aqueous solution of one or more tonicity-adjusting
substances (e.g. salts of plasma cations with biocompatible counterions), sugars (e.g.
glucose or sucrose), sugar alcohols (e.g. sorbitol or mannitol), glycols (e.g. glycerol), or
other non-ionic polyol materials (e.g. polyethyleneglycols, propylene glycols and the
like). The biocompatible carrier may also comprise biocompatible organic solvents such
as ethanol. Such organic solvents are useful to solubilise more lipophilic compounds or
formulations. Preferably the biocompatible carrier is pyrogen-free water for injection,
isotonic saline or an aqueous ethanol solution. The pH of the biocompatible carrier for
intravenous injection is suitably in the range 4.0 to 10.5.
In a yet further aspect, the present invention provides for use of the pharmaceutical
composition of the invention in a medical method, wherein said medical method is
preferably either a method for treatment or a method for diagnosis of a pathological
condition. In particular, the pharmaceutical composition of the present invention is
useful in the treatment or diagnosis of a pathological condition comprising inflammation.
Where the composition of the invention is an in vivo imaging composition as referred to
above, i.e. wherein R6 comprises [1 F]fluoro, the medical method is preferably a method
of in vivo imaging comprising:
(i) administering said pharmaceutical composition to a subject;
(ϋ) detecting signals emitted by the [1 F]fluoro comprised in said
pharmaceutical composition;
(iii) generating an image representative of the location and/or amount of said
signals.
The "subject" of the invention can be any human or animal subject. Preferably the
subject of the invention is a mammal. Most preferably, said subject is an intact
mammalian body in vivo. In an especially preferred embodiment, the subject of the
invention is a human.
"Administering" the in this in vivo imaging method is preferably carried out parenterally,
and most preferably intravenously.
The "detecting " step of the method of the invention involves detection of signals emitted
by the [1 F]fluoro by means of a detector sensitive to said signals, i.e. a positronemission
tomography (PET) detector.
The "generating " step of the method of the invention is carried out by a computer which
applies a reconstruction algorithm to the acquired signal data to yield a dataset. This
dataset is then manipulated to generate images showing the location and/or amount of
signals emitted by said [1 F]fluoro.
The in vivo imaging composition of the invention is readily obtained by reaction with
[1 F]fluoride of a precursor composition as defined above, i.e. a composition of the
invention wherein R6 comprises a leaving group as defined hereinabove. [1 F]-fluoride
ion (1 Fo) is normally obtained as an aqueous solution from the nuclear reaction
1 0(p,n) 1 F and is made reactive by the addition of a cationic counterion and the
subsequent removal of water. Removal of water is commonly carried out by application
of heat and use of a solvent such as acetonitrile to provide a lower boiling azeotrope. A
"cationic counterion" is a positively-charged counterion examples of which include large
but soft metal ions such as rubidium or caesium, potassium complexed with a cryptand,
or tetraalkylammonium salts. A preferred cationic counterion is a metal complex of a
cryptand, most preferably wherein said metal is potassium and wherein said cryptand is
Kryptofix 222.
In another aspect the present invention provides the pharmaceutical composition of the
invention for use in any of the above-defined medical methods.
In a yet further aspect, the present invention provides for use of the composition of the
invention in the manufacture of the pharmaceutical composition of the invention for use
in any of the above-defined medical methods.
In a further aspect the present invention provides a kit suitable for making the in vivo
imaging composition of the invention, wherein said kit comprises said precursor
composition. A specialised kit, or "cassette", may be used to prepare the in vivo
imaging composition of the present invention on an automated radiosynthesis apparatus.
By the term "cassette" is meant a piece of apparatus designed to fit removably and
interchangeably onto an automated radiosynthesis apparatus, in such a way that
mechanical movement of moving parts of the synthesizer controls the operation of the
cassette from outside the cassette, i.e. externally. [1 F]-radiotracers are now often
conveniently prepared on automated radiosynthesis apparatuses. By the term
"automated radiosynthesis apparatus" is meant an automated module based on the
principle of unit operations as described by Satyamurthy et al (1999 Clin Positr Imag;
2(5): 233-253). The term "unit operations " means that complex processes are reduced
to a series of simple operations or reactions, which can be applied to a range of
materials. Such automated radiosynthesis apparatuses are commercially available from a
range of suppliers (Satyamurthy et al, above), including: GE Healthcare; CTI Inc; Ion
Beam Applications S.A. (Chemin du Cyclotron 3, B-1348 Louvain-La-Neuve, Belgium);
Raytest (Germany) and Bioscan (USA).
A commercial automated radiosynthesis apparatus also provides suitable containers for the
liquid radioactive waste generated as a result of the radiosynthesis. Automated
radiosynthesis apparatuses are not typically provided with radiation shielding, since they are
designed to be employed in a suitably configured radioactive work cell. The radioactive
work cell provides suitable radiation shielding to protect the operator from potential
radiation dose, as well as ventilation to remove chemical and/or radioactive vapours.
Suitable cassettes comprise a linear array of valves, each linked to a port where reagents or
vials can be attached, by either needle puncture of an inverted septum-sealed vial, or by gastight,
marrying joints. Each valve has a male-female joint which interfaces with a
corresponding moving arm of the automated radiosynthesis apparatus. External rotation of
the arm thus controls the opening or closing of the valve when the cassette is attached to the
automated radiosynthesis apparatus. Additional moving parts of the automated
radiosynthesis apparatus are designed to clip onto syringe plunger tips, and thus raise or
depress syringe barrels.
The cassette is versatile, typically having several positions where reagents can be attached,
and several suitable for attachment of syringe vials of reagents or chromatography cartridges
(e.g. for SPE). The cassette always comprises a reaction vessel. Such reaction vessels are
preferably 0.5 to 10 mL, more preferably 0.5 to 5 mL and most preferably 0.5 to 4 mL in
volume and are configured such that 3 or more ports of the cassette are connected thereto,
to permit transfer of reagents or solvents from various ports on the cassette. Preferably the
cassette has 15 to 40 valves in a linear array, most preferably 20 to 30, with 25 being
especially preferred. The valves of the cassette are preferably each identical, and most
preferably are 3-way valves. The cassettes are designed to be suitable for
radiopharmaceutical manufacture and are therefore manufactured from materials which are
of pharmaceutical grade and ideally also are resistant to radiolysis.
Preferred automated radiosynthesis apparatuses of the present invention comprise a
disposable or single use cassette which comprises all the reagents, reaction vessels and
apparatus necessary to carry out the preparation of a given batch of the in vivo imaging
composition of the invention.
The following non-limiting examples serve to illustrate the invention in more detail.
Brief Description of the Examples
Example 1 describes a method to obtain a composition comprising a compound of
Formula I as defined herein and a compound of Formula II as defined herein, wherein a
prior art method is compared with the method of the present invention.
List of Abbreviations used in the Examples
OMs: mesylate
Example 1: Synthesis of N,N-diethyl-9-(2-f F]fluoroethyl)-5-methoxy-2,3,4,9-
tetrahydro-lH-carbazole-4-carboxamide
The compound N,N-diethyl-9-(2-[ 1 F]fluoroethyl)-5-methoxy-2,3,4,9-tetrahydro-lHcarbazole-
4-carboxamide was synthesised using the following steps:
Step 1: Synthesis of ethyl 3-bromo-2-oxocyclohexanecarboxylate
1 2
Step 2: Synthesis ofN-(2-(benzyloxy)ethyl)-2-chloro-5-methoxyaniline
Step 3: Synthesis of ethyl 3-((2-(benzyloxy)ethyl)(2-chloro-5-methoxyphenyl)amino)-2-
hydroxycyclohex-l-enecarboxylate
Step 4: Synthesis of ethyl 9-(2-(benzyloxy)ethyl)-8-chloro-5-methoxy-2,3,4,9-
tetrahydro-lH-carbazole-4-carboxylate
Step 5: Synthesis of 9-(2-(benzyloxy)ethyl)-8-chloro-5-methoxy-2,3,4,9-tetrahydro-1Hcarbazole-
4-carboxylic acid
Step 6: Synthesis of 9-(2-(benzyloxy)ethyl)-8-chloro-5-methoxy-2,3,4,9-tetrahydro-1Hcarbazole-
4-carbonyl chloride
8
Step 7: Synthesis of 9-(2-(benzyloxy)ethyl)-8-chloro-N,N-diethyl-5-methoxy-2,3,4,9-
tetrahvdro-lH-carbazole-4-carboxamide
10
Step 8: Synthesis of9-(2-(benzyloxy)ethyl)-N,N-diethyl-5-methoxy-2,3,4,9-tetrahydrolH-
carbazole-4-carboxamide
Step 9: Synthesis of N,N-diethyl-9-(2-hydroxyethyl)-5-methoxy-2,3,4,9-tetrahydro-1Hcarbazole-
4-carboxamide
12
11
Step 10: Synthesis of 2-(4-(diethylcarbamoyl)-5-methoxy-3,4-dihydro-lH-carbazol-
9(2H)-yl)ethyl methanesulfonate
12
13
Step 11: Synthesis of N,N-diethyl-9-(2-[ F]fluoroethyl)-5-methoxy-2,3,4,9-tetrahydrolH-
carbazole-4-carboxamide
13
14
In the prior art method (Wadsworth et al WO 2010/109007 Example 1), intermediate 10
above was purified by crystallization from diethyl ether (Wadsworth et al WO
2010/109007 Example l(i)). The method of the present invention was carried out as
generally described by Wadsworth et al (WO 2010/109007). However, in the method of
the present invention, intermediate 10 was purified by crystallization from diethyl ether
in the presence of diethyl amine.
Table 1: shows the per cent yield of the desired product along with the amount of
incorrect isomer impurity (where measured) in brackets thereafter. With the method of
the invention it can be seen that the amount of the incorrect isomer in intermediate 10,
which was purified using the method of the invention was only 0.2%.

Claims
A composition comprising a compound of Formula I
wherein:
R1 is hydrogen, Ci_3 alkyl, Ci_3 alkoxy, or halo;
R2 is hydroxyl, halo, cyano, Ci_3 alkyl, Ci_3 alkoxy, Ci_3 fluoroalkyl, or Ci_3
fluoroalkoxy;
3 7 R is -N-R R8 wherein R7 and R8 are hydrogen, Ci_6 alkyl, C7- io arylalkyl or,
together with R7, forms a nitrogen-containing C4 6 aliphatic ring;
R4 is O, S, SO, S0 2 or CH2;
R5 is CH2, CH2-CH2, CH(CH 3)-CH 2 or CH2-CH 2-CH 2;
R6 is -A^R 9 wherein A1 is a bond or Ci_i0 alkylene, and R9 is hydrogen, fluoro or a
leaving group, or R9 is the group -O-R 1 wherein R1 is hydrogen, Ci_3 alkyl, C3_6
aryl, C7_i 0 arylalkyl, or a hydroxyl protecting group;
wherein said composition comprises no more than 1% of a compound of Formula II:
( )
wherein R2 to R6 are as defined for Formula I .
The composition as defined in Claim 1 wherein R1 is halo.
The composition as defined in either Claim 1 or Claim 2 wherein R1 is chloro or
bromo.
The composition as defined in any one of Claims 1-3 wherein R1 is chloro.
The composition as defined in any one of Claims 1-4 wherein R6 is-A^R 9 wherein
A1 is Ci-io alkylene and R9 is the group -O-R 1 wherein R1 is C7- io arylalkyl or a
hydroxy 1protecting group.
(6) The composition as defined in any one of Claims 1-5 R is-A^R 9 wherein A1is C1-10
alkylene and R is the group -O-R and wherein Rio .is a hydro xyl protecting group.
The composition as defined in Claim 1 wherein R1 is hydrogen.
The composition as defined in either Claim 1 or Claim 7 wherein R6 is -A^R
wherein A1 is Ci_i0 alkylene and R9 is hydrogen, fluoro or a leaving group.
The composition as defined in any one of Claims 1, 7 or 8 wherein R6 is -A^R
wherein A1 is Ci_i0 alkylene and R9 is hydrogen.
The composition as defined in any one of Claims 1, 7 or 8 wherein R6 is -A^R
wherein A1 is Ci_i0 alkylene and R9 is a leaving group.
The composition as defined in any one of Claims 1, 7 or 8 wherein R6 is -A^R
wherein A is Ci-io alkylene and R is fluoro.
The composition as defined in any one of Claims 1, 7, 8 or 11 wherein R6 is -A^R
wherein A 1 is Ci_i0 alkylene and R9 is [1 F]fluoro.
The composition as defined in any one of Claims 1-12 wherein said composition
comprises the S-enantiomer of said compound of Formula I and said compound of
Formula II.
The composition as defined in any one of Claims 1-13 wherein R6 is -A^R 9 wherein
A 1 is Ci-3 alkylene.
The composition as defined in any one of Claims 1-14 wherein R6 is -A^R 9 wherein
A 1 is ethylene.
(16) The composition as defined in any one of Claims 1-15 wherein R2 is halo, C 1-
alkoxy or C 1- fluoroalkoxy.
(17) The composition as defined in any one of Claims 1-16 wherein R2 is halo or C 1-3
alkoxy.
(18) The composition as defined in any one of Claims 1-17 wherein R2 is fluoro or
methoxy.
(19) The composition as defined in any one of Claims 1-18 wherein R2 is methoxy.
(20) The composition as defined in any one of Claims 1-19 wherein R is -N-R R8
wherein R7 and R8 are Ci_6 alkyl or C7-10 arylalkyl.
(21) The composition as defined in any one of Claims 1-20 wherein R is -N-R R8
wherein R7 and R8 are C 1-3 alkyl.
(22) The composition as defined in any one of Claims 1-21 wherein R3 is -N-R R8
wherein R7 and R8 are both ethyl.
(23) The composition as defined in any one of Claims 1-22 wherein R4 is CH2.
The composition as defined in any one of Claims 1-23 wherein R is CH2-CH2.
The composition as defined in any one of Claims 1-24 which comprises no more
than 0.5% of said compound of Formula II.
The composition as defined in Claim 25 which comprises no more than 0.3% of said
compound of Formula II.
The composition as defined in any one of Claims 1-26 wherein said compound of
Formula I is a compound of Formula la:
wherein:
R is as defined in any one of Claims 1-3 and 7;
R2 is as defined in any one of Claims 1 and 16-19;
R and R8 are as defined in any one of Claims 1 and 20-22;
R9 and A1 are as defined in any one of Claims 1, 5, 6, 8-12, 14 and 15;
and said compound of Formula II is a compound of Formula Ila:
wherein each of R2, R7, R8, R9 and A1 are as defined for Formula la.
(28) The composition as defined in Claim 27 wherein:
R1 is hydrogen;
fluoro or methoxy;
R and R8 are C -6 alkyl;
hydrogen, fluoro or a leaving group; and,
A1 is Ci-io alkylene.
(29) The composition as defined in either Claim 27 or Claim 28 wherein:
R1 is hydrogen;
R2 is methoxy;
R7 and R8 are G-3
alkyl;
R9 is [1 F]fluoro or an aryl or alkyl sulfonate; and,
A1 is - alkylene.
(30) The composition as defined in any one of Claims 27-29 wherein:
R1 is hydrogen;
R2 is methoxy;
R7 and R8 are methyl or ethyl;
R9 is [1 F]fluoro, tosylate, triflate, nosylate or mesylate; and,
A1 is Ci-3 alkylene.
(31) The composition as defined in any one of Claims 27-30 wherein:
R1 is hydrogen;
R2 is methoxy;
R and R8 are both ethyl;
R9 is [1 F]fluoro or mesylate; and,
A1 is ethylene.
(32) A method to obtain the composition as defined in any one of Claims 1-31 wherein
said method comprises crystallization of a reaction mixture comprising said
compound of Formula I as defined in any one of Claims 1-24 and 27-31, and said
compound of Formula II as defined in any one of Claims 1, 5, 6, 8-24 and 27-31,
wherein said crystallization is carried out in a suitable organic solvent in the
presence of a catalytic amount of a weak organic base in order to obtain said
composition.
(33) The method as defined in Claim 32 wherein said weak organic base is selected from
N,N-diisopropyl ethylamine or diethyl amine.
(34) The method as defined in either Claims 32 or Claim 33 wherein said reaction
mixture is obtained using a method comprising cyclization of a compound of
Formula III:
wherein:
R is as defined in any one of Claims 1-3 and 7;
R2 is as defined in any one of Claims 1 and 16-19;
R is as defined in any one of Claims 1 and 20-22;
R4 is as defined in either Claim 1 or Claim 23;
R is as defined in either Claim 1 or Claim 24; and,
R6 is as defined in any one of Claims 1, 5, 6, 8-12, 14 and 15;
wherein said cyclization is carried out by reaction of said compound of Formula III
with a zinc halide.
(35) The method as defined in Claim 34 wherein said zinc halide is zinc chloride or zinc
bromide.
(36) The method as defined in either Claim 34 or Claim 35 wherein said zinc halide is
zinc chloride.
(37) A pharmaceutical composition comprising the composition as defined in any one of
Claims 1-31 together with a biocompatible carrier suitable for mammalian
administration.
(38) Use of the pharmaceutical composition as defined in Claim 37 in a medical method.
(39) The use as defined in Claim 38 wherein said medical method is treatment of a
pathological condition.
(40) The use as defined in Claim 39 wherein said medical method is diagnosis of a
pathological condition.
(41) A method of in vivo imaging comprising:
(i) administering to a subject the pharmaceutical composition as defined in
Claim 37 wherein R9 is [1 F]fluoro;
(ii) detecting signals emitted by the [1 F]fluoro comprised in said
pharmaceutical composition;
(iii) generating an image representative of the location and/or amount of said
signals.
(42) A kit comprising the composition as defined in Claim 1 any one of Claims 1-4, 7,
8, 10 and 13-27 wherein R6 is -A^R wherein A1 is a bond or Ci_io alkylene, and
R9 is a leaving group.
(43) The kit as defined in Claim 42 which is a cassette for use with an automated
radiosynthesis apparatus.