FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule13)
1. TITLE OF THE INVENTION
A process for preparation of pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid.
2. APPLICANT
(a). NAME: WOCKHARDT LIMITED
(b). NATIONALITY: INDIAN
(c). ADDRESS: D-4, M.I.D.C INDUSTRIAL AREA,
CHIKALTHANA, AURANGABAD - 431 210 (M.S.) INDIA.
The following specification particularly describes the invention and the manner
in which it is to be performed.

FIELD OF THE INVENTION
The invention relates to a process for the preparation of pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid.
BACKGROUND OF THE INVENTION
The compound of Formula (I), chemically known as S-(-)-9-fluoro-8-(4-hydroxy piperidin-1-yl)-5-methyl-6, 7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid, belongs to a class of antibacterial agents generally known as flouroquinolones and is useful in treating a broad range of bacterial infections.

Studies have shown that the administration of a compound of Formula (I) results in the formation of various metabolites. The preparation and purification of these metabolites is useful in understanding the drug metabolism and also in the quantification of these metabolites in animal as well as human clinical trials.
The administration of a compound of Formula (I) is known to result in the formation of S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid.
Morita et al (Chemical & Pharmaceutical Bulletin, 1990, 38(7), 2027-29) described a process for the synthesis of S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid (Scheme 1).


It is one of the objects of the present invention to prepare pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid.
SUMMARY OF THE INVENTION
Accordingly, there is provided a pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid and a process for it’s preparation.
In one general aspect, there is provided S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC.
In another general aspect, there is provided S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC, further containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j] quinolizine-2-carboxylic acid.
In yet another general aspect, there is provided a process for the preparation of pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to the invention, said process comprising:

(a) contacting S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j] quinolizine-2-carboxylic acid with chlorosulfonic acid in presence of diisopropylethylamine,
(b) neutralizing the reaction mixture obtained in step (a) above to a pH of about 5 to 6 to obtain crude S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid,
(c) suspending crude S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid obtained in step (b) in DM water and refluxing the resultant suspension to obtain a clear solution, and
(d) cooling the clear solution obtained in step (c) to obtain pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid.
In a further general aspect, there are provided pharmaceutical compositions comprising pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to the invention.
The details of one or more embodiments of the inventions are set forth in the description below. Other features, objects and advantages of the inventions will be apparent from the following description including claims.
BRIEF DESCRIPTION OF FIGURES
Figure 1 is a X-ray powder diffraction (XRPD) pattern of pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to the invention.
Figure 2 is a X-ray powder diffraction (XRPD) pattern of pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to the invention, which is kept at 26% relative humidity for 5 days.

Figure 3 is X-ray powder diffraction (XRPD) pattern of pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to the invention, which is kept at 78% relative humidity for 5 days.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made to the exemplary embodiments, and specific language will be used herein to describe the same. It should nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention. It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise.
The invention provides pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid.
The term “pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid” as used herein refers to S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having one or more of the following specifications:
(i) S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC;
(ii) S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC, further containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid;

(iii) S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC, optionally containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid, and having a X-ray powder diffraction pattern comprising peaks at about 4.9 ± 0.2, 8.1 ± 0.2, 9.8 ± 0.2, 12.2 ± 0.2, 15.2 ± 0.2, and 19.8 ± 0.2 degrees 2θ; or
(iv) S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC, optionally containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid, and having a X-ray powder diffraction pattern substantially in accordance with Figure 1.
In some embodiments, there is provided S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC.
In some other embodiments, there is provided S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy - piperidin-1-yl) -5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid.
In some embodiments, there is provided S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy -piperidin-1-yl) -5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC, further containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid.
In some embodiments, there is provided S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC, optionally containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid , further having a X-ray powder diffraction pattern

comprising peaks at about 4.9 ± 0.2, 8.1 ± 0.2, 9.8 ± 0.2, 12.2 ± 0.2, 15.2 ± 0.2, and 19.8 ± 0.2 degrees 2θ.
In some embodiments, there is provided S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC, optionally containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid , and having a X-ray powder diffraction pattern substantially in accordance with Figure 1.
In another general aspect, there is provided a process for preparing pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to the invention, said process comprising:
(a) contacting S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j] quinolizine-2-carboxylic acid with chlorosulfonic acid in presence of diisopropylethylamine,
(b) neutralizing the reaction mixture obtained in step (a) to pH of about 5 to 6 to obtain crude S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid,
(c) suspending crude S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid obtained in step (b) in DM water and refluxing the resultant suspension to obtain a clear solution, and
(d) cooling the clear solution obtained in step (c) to obtain pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid.
In some embodiments, the neutralization of the reaction mixture in step (b) above according the invention is achieved using hydrochloric acid.

In another general aspect, there is provided a pharmaceutical composition comprising pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to the invention.
In some other embodiments, the pharmaceutical compositions according to the invention may further comprise one or more pharmaceutically acceptable excipients.
It will be readily apparent to one skilled in the art that varying substitutions and modifications may be made to the invention disclosed herein without departing from the scope and spirit of the invention. For example, those skilled in the art will recognize that the invention may be practiced using a variety of different compounds within the described generic descriptions.
EXAMPLES
The following examples illustrate the embodiments of the invention that are presently best known. However, it is to be understood that the following are only exemplary or illustrative of the application of the principles of the present invention. Numerous modifications and alternative compositions, methods, and systems may be devised by those skilled in the art without departing from the spirit and scope of the present invention. The appended claims are intended to cover such modifications and arrangements. Thus, while the present invention has been described above with particularity, the following examples provide further detail in connection with what are presently deemed to be the most practical and preferred embodiments of the invention.
Example 1.
Preparation of S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid
The title compound was typically prepared using a synthetic procedure given in Scheme 2.


Scheme 2
20 gm (0.055 mole) of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j] quinolizine-2-carboxylic acid was dissolved in 400 ml dichloromethane. To this was added 40 ml (0.31 mole) diisopropylethylamine with stirring at 25 0C. 7.4 ml (0.063 mole) chlorosufonic acid was added slowly, after 20 minutes the reaction mixture was heated to 50 0C under stirring for 18 hrs. The reaction mixture was cooled to 25 0C and neutralized to pH 5-6 by using concentrated hydrochloric acid. Solid precipitated in the reaction mixture was filtered under suction and washed with acetone and air dried at suction to provide 5.0 gm (21%) as off white powder. Moisture content of the sample was 9.54% with 99.24% HPLC purity. Molecular formula is C19H21FN2O7S. Mass m/z is 439.2 (M - H).
The HPLC analysis was done using HP-1100 (Agilent Technologies) instrument and the typical analysis conditions were as follows: Column: Discovery C18; Buffer: 0.05M Amm. Acetate, pH: 4.5 by formic acid; Mobile Phase A: Buffer; Mobile Phase B: ACN by gradient; Flow: 1 ml/min; UV: 298nm; Oven Temperature: 35°C.
The above synthetic method gave good HPLC purity of synthesized compound with 0.54% of starting material as a single largest impurity. However, on standing for 3-4 weeks at standard conditions the impurity grew to 2-5% and it kept on increasing. The use of title compound so obtained was not suitable for any quantification or validation purpose, because of its decreasing purity profile.
To obtain a stable title compound, following procedure was followed. 48 gm of the title compound obtained above was suspended in 750 ml of DM water. The suspension was refluxed at about 110°C for about 30 minutes to obtain a clear solution. Then the solution was cooled to about -5°C gradually and stirring continued for about 3 hr. Solid separated was filtered, washed with about 100 ml cold water and dried on vacuum to provide 41 gm (85%) as off white powder. Moisture content of the sample was 16.79% with HPLC purity 99.91%.

The title pure compound (S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid) thus obtained contained less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid.
The pure title compound was also analyzed using various method of analysis as given below:
Molecular formula: C19H21FN2O7S.
Mass m/z: 439.2 (M - H)
H1NMR (DMSO-d6) δ: 1.38 (3H, d, J = 6.6 Hz), 1.60-2.20 (6H, m), 2.80-3.40 (6H, m), 4.30 (1H, m), 4.65 (1H, m), 7.62 (1H, d, J = 12.20 Hz) and 8.70 (1H, s).
IR (KBr): 1720, 1625, 1568, 1449, 1259 cm-1
The title compound was also analyzed using X-ray powder diffraction (XRPD) technique and a typical XRPD pattern is shown in Figure 1. As can be seen the pure title compound showed crystalline nature with sharp peaks.
The pure title compound obtained above was analyzed for stability and impurity profiles at various relative humidity conditions over a time period. Typically, the stability and impurity profile of the pure title compound was investigated for 5 days (at 26% relative humidity) and 5 days (at 78% relative humidity). At the end of the study period, the sample was analyzed with HPLC and XRPD. The results showed that the pure title compound retained its purity and XRPD pattern at the end of study period (no change in HPLC purity and XRPD pattern even after 5 days at 26% or 78% relative humidity), confirming that the compound thus obtained had improved stability.

WE CLAIM:
1. S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid having a purity of at least 99.9% as measured by HPLC.
2. S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to Claim 1, further containing less than 0.1% of S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid.
3. S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to Claim 1 or 2, further having a X-ray powder diffraction pattern comprising peaks at about 4.9 ± 0.2, 8.1 ± 0.2, 9.8 ± 0.2, 12.2 ± 0.2, 15.2 ± 0.2, and 19.8 ± 0.2 degrees 2θ.
4. S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to Claim 1 or 2, further having a X-ray powder diffraction pattern substantially in accordance with Figure 1.
5. A process for preparing S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to any of Claims 1-5, said process comprising:

(a) contacting S-(-)-9-fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo[i, j] quinolizine-2-carboxylic acid with chlorosulfonic acid in presence of diisopropylethylamine,
(b) neutralizing the reaction mixture obtained in step (a) to pH of about 5 to 6 to obtain crude S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid,
(c) suspending crude S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid obtained in step (b) in DM water and refluxing the resultant suspension to obtain a clear solution, and

(d) cooling the clear solution obtained in step (c) to obtain pure S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid.
6. A process according to Claim 5, wherein the neutralization of the reaction mixture in step (b) is achieved using hydrochloric acid.
7. A pharmaceutical composition comprising S-(-)-9-fluoro-8-(4-hydroxysulfonyloxy-piperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H, 5H-benzo [i, j] quinolizine-2-carboxylic acid according to any of the Claims 1-5.
8. A pharmaceutical composition according to Claim 7, further comprising one or more pharmaceutically acceptable excipients.