DESC:1. A process for preparation of a compound of Formula (I), comprising:

(a) reacting a compound of Formula (II) with a compound of Formula (III) to obtain a compound of Formula (IV);

(b) hydrogenolysis of a compound of Formula (IV) to obtain a compound of Formula (V);

(c) converting a compound of Formula (V) to obtain a compound of Formula (VI); and

(d) converting a compound of Formula (VI) to obtain a compound of Formula (I).

2. A process according to Claim 1, wherein a compound of Formula (IV) is obtained by reacting a compound of Formula (II) with a compound of Formula (III) in presence of 1-hydroxybenzotriazole and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.

3. A process according to Claim 1, wherein a compound of Formula (V) is obtained by hydrogenolysis of a compound of Formula (IV) in presence of a transition metal catalyst and a hydrogen source.

4. A process according to Claim 3, wherein the transition metal catalyst is palladium on carbon and hydrogen source is hydrogen gas.

5. A process according to Claim 1, wherein a compound of Formula (VI) is obtained by sulphonating a compound of Formula (V), followed by treatment with tetrabutyl ammonium acetate.
6. A process according to Claim 5, wherein the sulfonation of a compound of Formula (V) is carried out in the presence of sulfur trioxide dimethylformamide complex.

7. A process according to Claim 1, wherein a compound of Formula (VI) is converted to a compound of Formula (I) in presence of trifluoroacetic acid.

8. A process for preparation of a compound of Formula (I), comprising:

(a) reacting a compound of Formula (II) with a compound of Formula (III) in presence of 1-hydroxybenzotriazole and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride to obtain a compound of Formula (IV);

(b) hydrogenolysis of a compound of Formula (IV) in presence of palladium on carbon and hydrogen gas to obtain a compound of Formula (V);

(c) sulfonating a compound of Formula (V) in presence of sulfur trioxide dimethylformamide complex, followed by treatment with terabutylammonium acetate to obtain a compound of Formula (VI); and

(d) reacting a compound of Formula (VI) with trifluoroacetic acid to obtain a compound of Formula (I).

9. A compound of Formula (I) in amorphous form.

10. A compound of Formula (I) in a crystalline form.

11. A compound of Formula (I) according to Claim 10, having an X-ray powder diffraction pattern comprising a peak selected the group consisting of 10.57 (± 0.2), 12.01 (± 0.2), 13.61 (± 0.2), 15.47 (± 0.2), 17.86 (± 0.2), 18.34 (± 0.2), 19.09 (± 0.2), 19.81 (± 0.2), 22.69 (± 0.2), 24.79 (± 0.2), 27.22 (± 0.2) and 33.41 (± 0.2) degrees 2 theta.

12. A compound of Formula (I) according to Claim 10, having an X-ray powder diffraction pattern comprising a peak selected the group consisting of 10.57 (± 0.2), 12.01 (± 0.2), 15.47 (± 0.2), 17.86 (± 0.2), 18.34 (± 0.2), 19.09 (± 0.2), 19.81 (± 0.2) and 22.69 (± 0.2) degrees 2 theta.

13. A compound of Formula (I) according to Claim 10, having an X-ray powder diffraction pattern substantially the same as shown in Figure 2.

14. A compound of Formula (I) having a purity of more than about 95% as determined by HPLC.

15. A process for preparation of compound of Formula (I) in crystalline form, comprising: (a) dissolving a compound of Formula (I) in water to obtain a homogeneous mixture; (b) adding isopropyl alcohol to the homogeneous mixture obtained in step (a); and (c) isolating a compound of Formula (I) in crystalline form.

16. A pharmaceutical composition comprising a compound of Formula (I) according to any of the Claims 9-14.
,CLAIMS:RELATED PATENT APPLICATION

This application claims priority to Indian Patent Application No. 194/MUM/2014 filed on January 21, 2014, the disclosures of which are incorporated herein by reference in its entirety as if fully rewritten herein.

FIELD OF THE INVENTION

The invention relates to a process for preparation of (2S, 5R)-7-oxo-N-[(3S)-pyrrolidin-3-yloxy]-6-(sulfooxy)-1,6-diazabicyclo[3.2.1]octane-2-carboxamide.

BACKGROUND OF INVENTION

A compound of Formula (I), chemically known as (2S, 5R)-7-oxo-N-[(3S)-pyrrolidin-3-yloxy]-6-(sulfooxy)-1,6-diazabicyclo[3.2.1]octane-2-carboxamide has antibacterial properties and is disclosed in PCT International Patent Application No. PCT/IB2013/053092.

SUMMARY OF THE INVENTION

In one general aspect, there is provided a process for preparation of a compound of Formula (I), comprising:

(a) reacting a compound of Formula (II) with a compound of Formula (III) to obtain a compound of Formula (IV);

(b) hydrogenolysis of a compound of Formula (IV) to obtain a compound of Formula (V);

(c) converting a compound of Formula (V) to obtain a compound of Formula (VI); and

(d) converting a compound of Formula (VI) to obtain a compound of Formula (I).
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.

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, 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. All references including patents, patent applications, and literature cited in the specification are expressly incorporated herein by reference in their entirety.

The term “OBn” as used herein refers to benzyloxy.

The term “EDC” as used herein refers to 1-ethyl-3-(3-dimethylamino propyl)carbodiimide.

The term “HOBt” as used herein refers to 1-hydroxybenzotriazole.

The term “TBAA” as used herein refers to tetrabutylammonium acetate.

The term “(Boc)2O” as used herein refers to di-tert-butyldicarbonate.

The term “pharmaceutically acceptable derivative” as used herein refers to and includes any pharmaceutically acceptable salt, pro-drugs, metabolites, esters, ethers, hydrates, polymorphs, solvates, complexes or adducts of a compound described herein which, upon administration to a subject, is capable of providing (directly or indirectly) the parent compound. For example, the term “antibacterial or a pharmaceutically acceptable derivative thereof” includes all derivatives of the antibacterial agent (such as salt, prodrugs, metabolites, esters, ethers, hydrates, polymorphs, solvates, complexes or adducts) which, upon administration to a subject, is capable of providing (directly or indirectly) the antibacterial compound.

In one general aspect, there is provided a process for preparation of a compound of Formula (I), comprising:


(a) reacting a compound of Formula (II) with a compound of Formula (III) to obtain a compound of Formula (IV);

(b) hydrogenolysis of a compound of Formula (IV) to obtain a compound of Formula (V);

(c) converting a compound of Formula (V) to obtain a compound of Formula (VI); and

(d) converting a compound of Formula (VI) to obtain a compound of Formula (I).

The compound of Formula (IV) is obtained by reacting a compound of Formula (II) with a compound of Formula (III) in presence of suitable coupling agent and in presence of suitable solvent. Typical, non-limiting examples of coupling agents include EDC hydrochloride, dicyclohexylcarbodiimide, diisopropylcarbodiimide (DIC), carbonyldiimidazole (CDI), pivalyl chloride, HOBt and the like. In some embodiments, compound of Formula (IV) is obtained by reacting a compound of Formula (II) with a compound of Formula (III) in presence of 1-hydroxybenzotriazole (HOBt) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC.HCl) at temperature of about 25°C for about 16 hour. In some embodiments, this reaction is carried out in presence of mixture of water and dimethylformamide (DMF) as reaction solvent.

The compound of Formula (V) is obtained by hydrogenolysis of a compound of a compound of Formula (IV). The hydrogenolysis reaction can be carried out using a suitable hydrogenolysis agent. In some embodiments, hydrogenolysis of a compound of Formula (IV) to obtain a compound of Formula (V) is carried out in presence of a transition metal catalyst and a hydrogen source. In some other embodiments, the transition metal catalyst is palladium on carbon, and hydrogen source is hydrogen gas. In some other embodiments, the hydrogenolysis reaction is carried out in presence of a suitable solvent such as dichloromethane. In some embodiments, the hydrogenolysis of a compound of Formula (IV) is carried in presence 10% palladium on carbon and about 50 psi hydrogen atmosphere at a temperature of about 25ºC for about 4 hour to obtain a compound of Formula (V).

The compound of Formula (VI) is obtained by sulfonating a compound of Formula (V), followed by treatment with tetrabutylammonium acetate. The sulfonation reaction can be carried out in presence of suitable sulfonating agents such as sulfur trioxide pyridine complex, sulfur trioxide dimethylformamide complex and the like. In some embodiments, the sulfonation of a compound of Formula (V) is carried out by action of sulfur trioxide-dimethylformamide complex (SO3-DMF) and in presence of dimethylformamide as solvent at temperature of about 10ºC. The sulfonation reaction is followed by treatment with tetrabutylammonium acetate to obtain a compound of Formula (VI).

The compound of Formula (VI) is converted to a compound of Formula (I) in presence of a suitable deprotecting reagent. In some embodiments, compound of Formula (VI) is converted to a compound of Formula (I) by reacting a compound of Formula (VI) with trifluoroacetic acid in presence of suitable solvent such as dichloromethane at temperature of about -10ºC for about 1 hour.

In some embodiments, compound of Formula (I) is prepared using a process described in Scheme 1.

In some embodiments, compound of Formula (I) is further converted to its pharmaceutically acceptable derivative. In some embodiments, compound of Formula (I) is converted to its corresponding sodium salt.

In some embodiments, there is provided a compound of Formula (I) in amorphous form. In some other embodiments, there is provided a pharmaceutical composition comprising a compound of Formula (I) in amorphous form.

In some embodiments, there is provided a compound of Formula (I) in a amorphous form and having an X-ray powder diffraction pattern substantially the same as shown in Figure 1.

In some other embodiments, there is provided a compound of Formula (I) in crystalline form. In some embodiments, there is provided a pharmaceutical composition comprising a compound of Formula (I) in crystalline form.

In some other embodiments, there is provided a compound of Formula (I) in a crystalline form and having an X-ray powder diffraction pattern comprising a peak selected from the group consisting of 10.57 (± 0.2), 12.01 (± 0.2), 13.61 (± 0.2), 15.47 (± 0.2), 17.86 (± 0.2), 18.34 (± 0.2), 19.09 (± 0.2), 19.81 (± 0.2), 22.69 (± 0.2), 24.79 (± 0.2), 27.22 (± 0.2) and 33.41 (± 0.2) degrees 2 theta.

In some other embodiments, there is provided a compound of Formula (I) in a crystalline form and having an X-ray powder diffraction pattern comprising a peak selected from the group consisting of 10.57 (± 0.2), 12.01 (± 0.2), 15.47 (± 0.2), 17.86 (± 0.2), 18.34 (± 0.2), 19.09 (± 0.2), 19.81 (± 0.2) and 22.69 (± 0.2) degrees 2 theta.

In some embodiments, there is provided a compound of Formula (I) in a crystalline form and having an X-ray powder diffraction pattern substantially the same as shown in Figure 2.
In some embodiments, there is provided a process for preparation of compound of Formula (I) in crystalline form, comprising: (a) dissolving a compound of Formula (I) in water to obtain a homogeneous mixture; (b) adding isopropyl alcohol to the homogeneous mixture obtained in step (a); and (c) isolating a compound of Formula (I) in crystalline form.

In some embodiments, there is provided a process for preparation of a compound of Formula (I), comprising:

(a) reacting a compound of Formula (II) with a compound of Formula (III) in presence of 1-hydroxybenzotriazole and 1-ethyl-3-(3-dimethylamino propyl)carbodiimide hydrochloride to obtain a compound of Formula (IV);

(b) hydrogenolysis of a compound of Formula (IV) in presence of palladium on carbon and hydrogen gas to obtain a compound of Formula (V);

(c) sulfonating a compound of Formula (V) in presence of sulfur trioxide _ dimethylformamide complex, followed by treatment with terabutylammonium acetate to obtain a compound of Formula (VI); and

(d) reacting a compound of Formula (VI) with trifluoroacetic acid to obtain a compound of Formula (I).

In some embodiments, there is provided a compound of Formula (I) having a purity of more than about 95% as determined by HPLC. In some embodiments, there is provided a pharmaceutical composition comprising a compound of Formula (I) having purity of more than about 95% as determined by HPLC.

In some embodiments, there is provided a process for preparation of a compound of Formula (III), comprising:

(a) decarboxylation of (2S, 4R)-4-hydroxy-2-pyrrolidinecarboxylic acid (L-hydroxyproline) (VII) and further reaction with ethanolic hydrochloric acid to obtain a compound of Formula (VIII);

(b) reacting a compound of Formula (VIII) with di-tert-butyldicarbonate to obtain a compound of Formula (IX);

(c) reacting a compound of Formula (IX) with N-hydroxyphthalimide to obtain a compound of Formula (X); and

(d) reacting a compound of Formula (X) with hydrazine hydrate to obtain compound of Formula (III).

In general, L-hydroxyproline (VII) is decarboxylated by heating at higher temperature in presence of suitable catalyst such as 2-cyclohexen-1-one and in presence of suitable solvent such as cyclohexanol. The decarboxylated product is isolated as hydrochloride salt of (3-(R)-hydroxypyrrolidine hydrochloride) (VIII). The compound of Formula (VIII) is reacted with di-tert-butyl dicarbonate [(Boc)2O] in presence of base such as triethylamine and in presence of catalyst such as 4-dimethylaminopyridine (DMAP) to obtain (3R)-1-(tert-butoxycarbonyl)-3-hydroxypyrrolidine (IX). The compound of Formula (IX) is first reacted with the solution of diisopropyl azodicarboxylate and triphenylphosphine in suitable solvent under stirring, followed by reaction with N-hydroxyphthalamide to obtain (S)-3-[(1,3-dihydro-1,3-dioxo-isoindol-2-yl)oxy]-pyrrolidine-1-carboxylic acid tert-butyl ester (X). The compound of Formula (X) is reacted with hydrazine hydrate in suitable solvent such as dichloromethane to obtain tert-butyl-(3S)-2-[(aminooxy) pyrrolidine-1-carboxylate of Formula (III). A schematic for synthesis of a compound of Formula (III) is given in Scheme-2.

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

Synthesis of tert-butyl (3S)-2-(aminooxy)pyrrolidine-1-carboxylate (III):

Step 1: Preparation of 3-(R)-hydroxypyrrolidine hydrochloride (VIII):

To a stirred suspension of commercially available (2S, 4R)-4-hydroxy-2-pyrrolidinecarboxylic acid (L-hydroxyproline) (VII) (100 g, 0.762 mol) in anhydrous cyclohexanol (500 ml), was added 2-cyclohexen-1-one (5 ml). The resulting mixture was heated under reflux at about 154°C for about 48 hour. The obtained clear solution was allowed to cool to room temperature and then was cooled further to 10°C. To this, about 15 % solution of hydrochloric acid in ethanol (234 ml) was added and then stirred for 30 minutes. The separated solid was filtered under suction and washed with ethyl acetate (2 × 100 ml). The solid was dried under reduced pressure to obtain 47.5 g of 3-(R)-hydroxypyrrolidine hydrochloride (VIII) in 51% yield. The solid was used without further purification in the next step.

Analysis:
Mass: 87.8 (M+1) as free base; for Molecular weight of 123.57 and Molecular Formula of C4H10ClNO; and
1H NMR (400MHz, DMSO): d 9.58 – 9.32 (brd, 2H), 5.36 (brs, 1H), 4.36 - 3.39 (brs, 1H), 3.17 (brs, 2H), 3.11-2.96 (dd, 2H), 1.90 – 1.81 (m, 2H).

Step 2: Preparation of (3R)-1-(tert-butoxycarbonyl)-3-hydroxypyrrolidine (IX):

To a stirred suspension of 3-(R)-hydroxypyrrolidine hydrochloride (VIII) (110 g, 0.9 mol) in dichloromethane (1100 ml), triethylamine (273 g, 2.7 mol) was added at 0-5°C. After 5 minute of stirring di-tert-butyldicarbonate [(Boc)2O] (245 g, 1.125 mol) was added to the reaction mixture in small portions, followed by 4-dimethylaminopyridine (10.99 g, 0.09 mol). The reaction mixture was stirred for 2 hour and then poured in to water (1100 ml). The organic layer was separated and washed with saturated ammonium chloride solution (1×1100 ml) and water (1100 ml). The organic layer was dried over anhydrous sodium sulphate and the solvent evaporated under reduced pressure. The residue was purified by silica gel (60-120 mesh) column chromatography using 1-5% mixtures of acetone: hexane as an eluent. The combined fractions were evaporated, to obtain the 118 g of (3R)-1-(tert-butoxycarbonyl)-3-hydroxypyrrolidine (IX), as a white solid, in 71% yield.

Analysis:
Melting point: 55 - 58°C;
Mass: 188 (M+1); for Molecular Weight of 187.24 and Molecular Formula of C9H17NO3; and
1H NMR (400MHz, CDCl3): d 4.428 – 4.424 (s, 1H), 3.46 – 3.43 (m, 2H), 3.37 – 3.28 (m, 2H), 2.36 – 2.30 (d, 1H), 2.00 – 1.86 (m, 2H), 1.44 (s, 9H).

Step 3: Preparation of (S)-3-[(1,3-dihydro-1,3-dioxo-isoindol-2-yl)oxy]pyrrolidine-1-carboxylic acid tert-butyl ester (X):

To a stirred solution of di-isopropyl azodicarboxylate (97.17 g, 0.481 mol) in tetrahydrofuran (1200 ml), a solution triphenyl phosphine (125.9 g, 0.481 mol) in tetrahydrofuran (300 ml) was added at temperature below -10°C. The resulting reaction mixture was stirred for further 45 minute at the same condition and a solution of (3R)-1-(tert-butoxycarbonyl)-3-hydroxypyrrolidine (IX) (60 g, 0.3204 mol) in tetrahydrofuran (300 ml) was added over a period of 15 minute. After another 45 minute of stirring, N-hydroxy phthalimide (52.4 g, 0.3204mol) was added in one portion to the reaction mass. The reaction mixture was allowed to warm to room temperature and stirred for 16 hour. The completion of the reaction was monitored by thin layer chromatography. After completion of reaction, the solvent was evaporated under reduced pressure. The residue thus obtained was stirred with di-isopropyl ether (600 ml). The precipitate formed was filtered under suction. The filtrate was concentrated under reduced pressure and the residual mass was purified by silica gel (60-120 mesh) column chromatography using 1-5 % mixtures of acetone: hexane as an eluent. The solvent from the combined fractions was evaporated to obtain 63 g of (S)-3-[(1,3-dihydro-1,3-dioxo-isoindol-2-yl)oxy]pyrrolidine-1-carboxylic acid tert-butyl ester (X), as a white solid, in 59% yield.

Analysis:
Melting point: 112-115°C;
Mass: 333.2 (M+1); for Molecular Weight of 332.36 and Molecular Formula of C17H2ON2O5; and
1H NMR (400 MHz, CDCl3): d 7.86-7.83 (m, 2H), 7.78-7.75 (m, 2H), 4.99 – 4.94 (d, 1H), 3.80 – 3.68 (m, 2H), 3.60 - 3.53 (m, 2H), 2.28-2.25 (m, 1H), 2.02 (m, 1H), 1.48 (s, 9H).

Step 4: Preparation of tert-butyl (3S)-2-(aminooxy)pyrrolidine-1-carboxylate (III):

To a stirred suspension of the (S)-3-[(1,3-dihydro-1,3-dioxo-isoindol-2-yl)oxy]pyrrolidine-1-carboxylic acid tert-butyl ester (X) (12.68 g, 0.0381 mol) in dichloromethane (200 ml) was added 99% hydrazine hydrate (3.81 g, 0.0762 mol) drop-wise over a period of 30 minutes, at 25°C. After 2 hour of stirring, the separated solid was filtered and washed with dichloromethane (2 × 50 ml).The filtrate and washings were combined and washed with water (2 × 65 ml) and finally with brine (1 × 65 ml). The organic layer was dried over anhydrous sodium sulphate and the solvent was evaporated under reduced pressure to obtain 7.71 g of tert-butyl (3S)-2-(aminooxy)pyrrolidine-1-carboxylate (III) as pale yellow oil.

Analysis:
Mass: 203 (M+1); for Molecular Weight of 202.26 and Molecular Formula of C9H18N2O3.

Example 2
Synthesis of (2S, 5R)-7-oxo-N-[(3S)-pyrrolidin-3-yl-oxy]-6-(sulfooxy)-1,6-diaza bicyclo[3.2.1]octane-2-carboxamide (I):

Step 1: Preparation of tert-butyl-(3S)-3-[({[2S, 5R)-6-(benzyloxy)-7-oxo-1,6-diazabicylco[3.2.1]oct-2-yl]carbonyl}amino)oxy]pyrrolidine-1-carboxylate (IV):
To a clear, stirred solution of sodium (2S, 5R)-6-(benzyloxy)-7-oxo-1,6-diazabicyclo[3.2.1]octane-2-carboxylate (II) (11.38 g, 0.0382 mol) in water (114 ml), was added EDC.HCl (18.24 g, 0.0955 mol) at 15°C, in small portions. After 10 minutes, a solution of tert-butyl-(3S)-3-(aminooxy) pyrrolidine-1-carboxylate (III, 7.72 g, 0.0382 mol), prepared as per the literature procedure: US5233053, Chemistry Letters, 893-896, (1986) and depicted in scheme 2), in dimethylformamide (24 ml) was added drop wise, to the above stirred solution, at about 10°C. The reaction mass was allowed to warm to 25°C and HOBt (5.15 g, 0.0382 mol) was added in small portions over a period of 15 minutes and the reaction mixture was stirred further at room temperature for 16 hour. After completion of the reaction (monitored by thin layer chromatography using solvent system acetone: hexane (35:65)) the resulting mixture was filtered and the residue was washed with water (120 ml). The residual white solid was suspended in fresh water (120 ml) and the mixture stirred at 50°C, for 3 hour. The resulting suspension was filtered and the residual solid dried under reduced pressure to obtain 16.1 g of tert-butyl (3S)-3-[({[2S,5R)-6-(benzyloxy)-7-oxo-1,6-diazabicylco[3.2.1]oct-2-yl]carbonyl}amino) oxy]pyrrolidine-1-carboxylate (IV) as off white solid in 92% yield.

Analysis:
Mass: 461.3 (M+1); for Molecular weight of 460.53 and Molecular formula of C23H32N4O6; and
1H NMR (400MHz, CDCl3): d 9.08-9.03 (d, 1H), 7.43-7.36 (m, 5H), 5.06-4.88 (dd, 2H), 4.63-4.57 (d, 1H), 3.97-.396 (d, 1H), 3.64-3.53 (m, 2H), 3.47-3.37 (m, 2H), 3.31 (s, 1H), 3.02-2.99 (d, 1H), 2.75-2.73 (d, 1H), 2.29(m, 2H), 2.18-2.15 (m, 1H), 2.01-1.90 (m, 3H), 1.66 (m, 1H), 1.46 (s, 9H).

Step 2: Preparation of tert-butyl-(3S)-3-[({[2S,5R)-6-hydroxy-7-oxo-1,6-diazabicylco [3.2.1]oct-2-yl]carbonyl}amino)oxy]pyrrolidine-1-carboxylate (V):

tert-Butyl-(3S)-3-[({[2S,5R)-6-(benzyloxy)-7-oxo-1,6-diazabicylco[3.2.1]oct-2-yl]carbonyl}amino)oxy]pyrrolidine-1-carboxylate (IV) (10 g, 0.02171 mol) was dissolved in a mixture of dimethylformamide and dichloromethane (1:1, 50 ml : 50 ml) to obtain a clear solution. To this solution, was added 10% palladium on carbon (2.5 g, 50% wet) catalyst. The suspension was stirred for 4 hour, at 50 psi hydrogen atmosphere, at 25°C. After completion of the reaction (monitored by thin layer chromatography), the resulting mixture was filtered through a celite pad. The residue was washed with dichloromethane (50 ml). The solvent from the combined filtrate was evaporated under reduced pressure to obtain 8.04 g of tert-butyl(3S)-3-[({[2S,5R)-6-hydroxy-7-oxo-1,6-diazabicylco[3.2.1]oct-2-yl]carbonyl
amino)oxy]pyrrolidine-1-carboxylate (V) as oil. This was used as such for the next reaction without further purification.

Analysis:
Mass: 371.2 (M+1); for Molecular Weight of 370.4 and Molecular Formula of C16H26N4O6.

Step 3: Preparation of tert-butyl-(3S)-3-[({[2S,5R)-6-(sulfooxy)-7-oxo-1,6-diazabicylco[3.2.1]oct-2-yl]carbonyl}amino)oxy]pyrrolidine-1-carboxylate, tetrabutyl ammonium salt (VI):

To a stirred solution of tert-butyl(3S)-3-[({[2S,5R)-6-hydroxy-7-oxo-1,6-diazabicylco[3.2.1]oct-2-yl]carbonyl}amino)oxy]pyrrolidine-1-carboxylate (V) (8.04 g, 0.0217 mol) in dimethylformamide (50 ml), was added sulfur trioxide dimethyl formamide complex (3.98 g, 0.0260 mol) in one portion, at about 10°C. The stirring was continued further for 30 minute and then the reaction mixture was allowed to warm to room temperature. After 2 hour, a solution of tetrabutylammonium acetate (7.83 g, 0.0260 mol) in water (25.8 ml) was added to the resulting reaction mass under stirring. After additional 2 hour of stirring, the solvent from the reaction mixture was evaporated under reduced pressure to obtain an oily residue. The oily mass was co-evaporated with xylene (2 × 20 ml) to obtain thick mass. This mass was partitioned between dichloromethane (100 ml) and water (100 ml). The organic layer was separated and the aqueous layer re-extracted with dichloromethane (50 ml). The combined organic extracts were washed with water (3 × 50 ml), dried over anhydrous sodium sulphate and the solvent evaporated under reduced pressure. The residual oily mass was triturated with ether (3 × 50 ml), each time the ether layer was decanted and finally the residue was concentrated under reduced pressure to obtain 11.3 g of tert-butyl(3S)-3-[({[2S,5R)-6-(sulfooxy)-7-oxo-1,6-diazabicylco[3.2.1]oct-2-yl]carbonyl}amino)oxy] pyrrolidine-1- carboxylate, tetrabutylammonium salt (VI), as a white foam, in 75 % yield.

Analysis:
Mass: 449.3 (M-1, without TBA); for Molecular weight of 691.94 and Molecular formula of C32H61N5O9S; and
1H NMR (400MHz, CDCl3): d 9.14-9.10 (d, 1H), 4.63 (s, 1H), 4.35 (s, 1H), 3.94-3.92 (d, 1H), 3.66-3.35 (m, 5H), 3.29-3.27 (m, 8H), 2.83-2.80 (d, 1H), 2.35-2.17 (m, 3H), 1.98-1.87 (m, 2H), 1.73 (m, 1H), 1.70-1.62 (m, 8H), 1.49-1.40 (m, 17H), 1.02-0.99 (t, 12H).

Step 4: Preparation of (2S,5R)-7-oxo-N-[(3S)-pyrrolidin-2-yl-oxy]-6-(sulfooxy)-1,6-diazabicyclo [3.2.1]octane-2-carboxamide (I):

To a stirred solution of tert-butyl(3S)-3-[({[2S,5R)-6-(sulfooxy)-7-oxo-1,6-diazabicylco[3.2.1]oct-2-yl]carbonyl}amino)oxy]pyrrolidine-1-carboxylate tetrabutyl ammonium salt (VI) (11 g, 0.0158 mol) in dichloromethane (55 ml), was added trifluoroacetic acid (55 ml) drop wise at about -10 °C over a period of 1 hour. After 1 hour of stirring, the resulting mixture was poured into hexane (550 ml), stirred well for 30 minute and the separated oily layer was collected. This procedure was repeated one more time and finally the combined oily layer was added to diethyl ether (110 ml) under vigorous stirring, at about 25°C. The ether layer was removed by decantation from the precipitated solid. This procedure was repeated twice again with diethyl ether (2 × 110 ml). The solid thus obtained was stirred with fresh dichloromethane (110 ml) for 30 minutes and filtered. The residual solid was dried at about 45 °C under reduced pressure to obtain 5.7 g of (2S,5R)-7-oxo-N-[(3S)-pyrrolidin-2-yl-oxy]-6-(sulfo-oxy)-1,6-diaza bicyclo[3.2.1] octane-2-carboxamide (I), as a white amorphous solid having XRPD as shown in Figure 1.

Analysis:
Mass: 349.2 (M-1); for Molecular Weight of 350.35 and Molecular Formula of C11H18N4O7S; and
1H NMR (400MHz, DMSO-D6): d 11.44 (brs, 1H), 8.80 (brs, 2H), 4.64-4.63 (m, 1H), 4.00 (s, 1H), 3.78-3.77 (d, 1H), 3.38-3.23 (m, 4H), 3.03-2.93 (dd, 2H), 2.48-2.11 (m, 1H), 2.00-1.94 (m, 2H), 1.88-1.86 (m, 1H), 1.71-1.65 (m, 2H).

Example 3

Preparation of Crystalline Form I of (2S,5R)-7-oxo-N-[(3S)-pyrrolidin-2-yl-oxy]-6-(sulfooxy)-1,6-diaza bicyclo[3.2.1] octane-2-carboxamide:

The solid (5 g) obtained in Step 4 of Example 2 was dissolved in water (30 ml) with stirring. To this solution, Isopropanol (210 ml) was slowly added at 25 °C and stirred for 12 hours. The separated solid was filtered and washed with additional isopropanol (10 ml) and dried under reduced pressure to obtain 3.9 g of (2S,5R)-7-oxo-N-[(3S)-pyrrolidin-2-yl-oxy]-6-(sulfo-oxy)-1,6-diazabicyclo[3.2.1]octane-2-carboxamide as crystalline Form I, having XRPD as shown in Figure 2, in 78 % yield.

Analysis:
Purity as determined by HPLC: 95.56 %; and
X-ray powder diffraction pattern comprising peak at (2 Theta Values): 10.57 (± 0.2), 12.01 (± 0.2), 13.61 (± 0.2), 15.47 (± 0.2), 17.86 (± 0.2), 18.34 (± 0.2), 19.09 (± 0.2), 19.81 (± 0.2), 22.69 (± 0.2), 24.79 (± 0.2), 27.22 (± 0.2) and 33.41 (± 0.2)

Typical X-ray analysis was performed as follows. Pass the test substance through sieve #100 BSS or gently grind it with a mortar and pestle. Place the test substance uniformly on a sample holder having cavity surface on one side, press the sample and cut into thin uniform film using a glass slide in such a way that the surface of the sample should be smooth and even. Record the X-ray diffractogram using the following instrument parameters.

Instrument : X-Ray Diffractometer
(PANalytical, Model X’Pert Pro MPD)
Target source : CuK(a)
Antiscattering slit (Incident beam) : 1°
Programmable Divergent slit : 10 mm (fixed)
Anti-scattering slit (Diffracted beam) : 5.5 mm
Step width : 0.02º
Voltage : 40 kV
Current : 40 mA
Time per step : 30 seconds
Scan range : 3 to 40º