DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003

COMPLETE SPECIFICATION
(Section 10 and Rule 13)

PREPARATION OF SUGAMMADEX OR SALTS THEREOF

AUROBINDO PHARMA LTD HAVING CORPORATE OFFICE AT
THE WATER MARK BUILDING,
PLOT NO.11, SURVEY NO.9,
KONDAPUR, HITECH CITY,
HYDERABAD, 500 084,
TELANGANA, INDIA
AN INDIAN ORGANIZATION

The following specification particularly describes and ascertains the nature of this invention and the manner in which the same is to be performed:
FIELD OF THE INVENTION
The present invention relates a process for the preparation of Sugammadex or salts thereof. Further, the present invention relates to a process for the preparation of Sugammadex lithium salt or cesium salt, and its conversion to Sugammadex sodium.

BACKGROUND OF THE INVENTION
Sugammadex is chemically known as Cyclooctakis-(l-—>4)-[6-S-(2-carboxyethyl)-6-thio-a-D-glucopyranosyl]. Sugammadex is marketed as Bridion® and structurally known as compound of formula I:

I

Sugammadex is a modified ?-cyclodextrin, with a lipophilic core and a hydrophilic periphery and indicated for the reversal of neuromuscular blockade induced by rocuronium bromide and vecuronium bromide in adults undergoing surgery. Sugammadex contains eight recurring amylose units each with five asymmetric carbon atoms, in total forty asymmetric carbon atoms for the whole molecule. The five original configurations of all asymmetric carbon atoms is retained during the synthetic manufacturing process.

WO 01/40316A1 describes Sugammadex sodium and its preparation. The process of WO ‘316 and process disclosed in WO 2012/025937A1 involve reaction of 6-per-deoxy-6-per-iodo-?-cyclodextrin with 3-mercaptopropionic acid in the presence of sodium hydride. The process briefly represented in the below:

WO 2014/125501 and WO 2017/089966A1 disclose preparation of Sugammadex sodium, which involves reaction of 6-perdeoxy-6-per-halo- ?-cyclodextrin with 3-mercaptopropionic acid in the presence of alkali metal alkoxides.

WO 2016/194001A1 discloses preparation of Sugammadex sodium, which involves reaction of 6-perdeoxy-6-per-halo-?-cyclodextrin with 3-mercaptopropionic acid in the presence of potassium hydroxide to obtain Sugammadex potassium, which is treated with hydrochloric acid to obtain Sugammadex free acid, which is finally reacted with sodium hydroxide to provide Sugammadex sodium. The WO ‘001 also discloses processes for Sugammadex sodium by using sodium hydroxide and sodium amide.

WO 2017/144734 discloses preparation of Sugammadex sodium, which involves reaction of 6-perdeoxy-6-per-halo- ?-cyclodextrin with 3-mercaptopropionic acid in the presence of sodium hydroxide.

WO 2017/163165A1 discloses preparation of Sugammadex sodium, which involves reaction of 6-perdeoxy-6-per-halo- ?-cyclodextrin with disodium salt of 3-mercaptopropionic acid.

However, processes provided in the literature suffer with the use of hazardous reagent and/or involve longer reaction time to obtain Sugammadex with lower yield and purity.

Therefore, there is a need to develop alternative and improved process for the preparation of Sugammadex sodium.

OBJECTIVE OF THE INVENTION
The objective of the present invention is to provide a process for the preparation of pure Sugammadex sodium.

Another objective of the present invention is to provide a process for the preparation of Sugammadex lithium salt by using lithium hydroxide, and its conversion to Sugammadex sodium.

Another objective of the present invention is to provide a process for the preparation of Sugammadex cesium salt by using cesium salt, and its conversion to Sugammadex sodium.

SUMMARY OF THE IVENTION
In an aspect of the present invention, there is provided a process for the preparation of Sugammadex sodium, which comprises:
a) reaction of 6-perdeoxy-6-per-halo- ?-cyclodextrin of Formula III:

Formula III
wherein X is halo is bromo, chloro or Iodo,

with 3-mercaptopropionic acid in presence of lithium hydroxide or cesium salt to provide Sugammadex salt thereof of Formula II; and

Formula II
wherein M is Cs or Li metal cation.

b) reaction of Sugammadex salt of Formula II with sodium base to provide Sugammadex sodium of Formula I.

In another aspect of the present invention, there is provided Sugammadex lithium in solid form characterized by X-ray powder diffraction pattern.

In another aspect of the present invention, there is provided Sugammadex cesium in solid form characterized by X-ray powder diffraction pattern.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is powder X-ray power diffraction ("PXRD") pattern of lithium salt of Sugammadex prepared according to the Example 4.

Figure 2 is powder X-ray power diffraction ("PXRD") pattern of cesium salt of Sugammadex prepared according to the Example 10.

DETAILED DESCRIPTION OF THE IVENTION
In an aspect of the present invention, there is provided a process for the preparation of Sugammadex sodium, which comprises:
a) reaction of 6-perdeoxy-6-per-halo- ?-cyclodextrin of Formula III:

Formula III
wherein X is halo is bromo, chloro or Iodo,

with 3-mercaptopropionic acid in presence of lithium hydroxide or cesium salt to provide Sugammadex salt thereof of Formula II; and

Formula II
wherein M is Cs or Li metal cation.

b) reaction of Sugammadex salt of Formula II with sodium base to provide Sugammadex sodium of Formula I.

Step a) involves reaction of 6-perdeoxy-6-per-halo- ?-cyclodextrin with 3-mercaptopropionic acid in presence of lithium hydroxide or cesium salt and in the presence of solvent.

The cesium salt comprises cesium hydroxide, cesium sulfate, and cesium carbonate or cesium formate. In an embodiment, the cesium salt is cesium carbonate.

The solvent comprises dimethylformamide (DMF), dimethylsulfoxide (DMSO), N-Methylpyrrolidine (NMP), Dimethylacetamide (DMAC), 1,4-dioxane, tetrahydrofuran (THF), 2-methyl tetrahydrofuran, chlorinated solvents such as dichloromethane (DCM), dichloroethane, alcohol such as methanol, ethanol, n-propanol, isopropanol, n-butanol, tert.butanol, esters such as ethyl acetate, methyl acetate, nitrile such as acetonitrile, ketone such as acetone and the like or mixtures thereof. In an embodiment, the solvent is selected from DMF, DMSO and DMA.

The reaction is carried out for a period of 1 hour to 7 hours or 2 hours 6 hours to complete.

In an embodiment, the step a) involves reaction of 3-mercaptopropionic acid with lithium hydroxide or cesium salt in presence of solvent at a temperature of -20 to 35°C or more for a period of 15 minutes to 1 hour or more to obtain salt of 3-mercaptopropionic acid. The salt of 3-mercaptopropionic acid may be used directly for the further reaction or it may be isolated by using suitable techniques such as anti-solvent, concentration by distillation, crash cooling and the like.

The resultant salt of 3-mercaptopropionic acid is reacted with 6-perdeoxy-6-per-halo- ?-cyclodextrin in presence of a solvent at an elevated temperature of about 40°C to about 150°C to obtain Sugammadex salt.

After completion of the reaction, the reaction mixture may be used directly for further conversion to Sugammadex sodium or it may be subjected for solid precipitation by using suitable techniques such as anti-solvent, concentration by distillation, cooling, crash cooling and the like or combination thereof.

In an embodiment of the present invention, there is provided Sugammadex Lithium salt, which is characterized by X-ray powder diffraction pattern.

In another embodiment of the present invention, there is provided Sugammadex Cesium salt, which is characterized by X-ray powder diffraction pattern.

In an embodiment of the present invention, there is provided a process for precipitation of Sugammadex salt in a solid form which comprises providing a solution of Sugammadex salt in a solvent at elevated temperature and cooling and/or combining with anti-solvent.

The solution may be obtained by the dissolution of Sugammadex salt in a solvent or obtained from the reaction of salt of 3-mercaptopropionic acid is reacted with 6-perdeoxy-6-per-halo- ?-cyclodextrin in a solvent.

The cooling temperature is less than 40°C or less than 30°C and the anti-solvent comprises alcohol such as methanol, ethanol, n-propanol, isopropanol, tert.butanol, n-butanol, acetone, acetonitrile and the like.

The term “pure”, as used in, unless specified otherwise, Sugammadex sodium having purity of greater than or equal to 90% or greater than or equal to 95% determined by HPLC.

The step b) of the present invention involves reaction of Sugammadex salt with sodium base such as sodium hydroxide.

The Sugammadex salt in solvent such as water or with mixture of water miscible solvent reacts with sodium base to obtain solution. The pH of solution may be about 9 to 14 or 11 to 13. The resultant solution may be treated with activated carbon or silica and then subjected for precipitation of solid addition of anti-solvent such as methanol, ethanol, n-propanol, and isopropanol or mixture thereof.

The process of present invention briefly represented in scheme-I:

Scheme-I
The another process of present invention briefly represented in scheme-II:

Scheme-II

An inventor of the present application, surprisingly, found that lithium hydroxide and cesium carbonate improves the yield, reduces the content of mercaptopropionic acid dimer impurity to less than 15% and reduces the reaction time to less than 7 hours.

In an embodiment, there is provided a process for the purification of Sugammadex sodium, which comprises:
a) providing a solution of Sugammadex sodium in water;
b) treating the solution with HCl to adjust the pH 6-8;
c) refluxing the solution of step b); and
d) adding alcohol to the solution of step c) to obtain pure Sugammadex sodium.
The alcohol used in step d) comprises methanol, ethanol, isopropyl alcohol, n-propanol, n-butanol, iso-butanol, tert-butyl alcohol or mixtures thereof.

Sugammadex sodium obtained from the present invention has purity greater than 95% by HPLC.

Having described the invention with reference to certain aspects and embodiments, which will become apparent to one skilled in the art from consideration of the specification. The invention is further defined by reference to the following examples. It will be apparent to those skilled in the art that many modifications, both to materials and methods, may be practiced without departing from the scope of the invention.

EXAMPLES
Example-1: Preparation of 6-perdeoxy-6-per-bromo gamma cyclodextrin.
Bromine (307.9 g, 1.926 eq.,) was added to dimethylformamide (700 mL) and Triphenylphosphine (262.09 g, 1.926 eq.,) at 25-35°C, the reaction was maintained for 1 hour at 0-10°C and washed the reaction mass with dichloromethane. Gamma cyclodextrin (100 g, 0.077 eq.,) was dissolved in dimethyl formamide and the solution was added to reaction mass at 0-10°C and heated the mass to 65-75°C, maintained for 24 hours at same temperature monitored the reaction progress by HPLC. The reaction mass was cooled to 0-10°C and water (2400 mL) was added. The pH of the reaction mass was adjusted to 10-12 with sodium methoxide solution. Methanol (1000 mL) was added to reaction mass at room temperature and stirred for 45 min. The precipitated compound was filtered and washed the wet compound with methanol (200 mL). The wet compound was taken into methanol (1000 mL) and stirred for 1.0 hr at room temperature. The obtained material was filtered and washed with methanol (200 mL) and dried at 55-65 °C.
Dry weight: 111.2 g; Yield: 80.6%

Example-2: Preparation of 6-perdeoxy-6-per-chloro gamma cyclodextrin:
Methanesulfonoyl chloride (176.6g, 1.51eq.,) was added to mixture of dimethylformamide (750 mL), imidazole (104.5 g, 1.541 eq.,) and gamma cyclodextrin (100.0 g, 0.77 eq.,) for 60 min at room temperature and heated to 65-70°C. The reaction mass was maintained for 24 hours at same temperature and monitored the reaction progress by HPLC. The reaction mass was cooled to 0-10°C and then water (2000 mL) was added. The pH of the reaction mass was adjusted to 10-12 with sodium hydroxide solution and stirred for 60 min at room temperature. The precipitated compound was filtered the and washed with water (200 mL). The wet compound taken into methanol (1000 mL) and stirred for 60 min at room temperature. The obtained material was filtered and washed with methanol (200 mL), dried at 55-65°C.
Dry weight: 85.6 g; Yield: 76.9 %

Example-3: Purification of 6-perdeoxy-6-per-bromo gamma cyclodextrin.
6-perdeoxy-6-per-bromo gamma cyclodextrin (100 g) taken into dimethyl formamide (500 mL) and isopropyl alcohol (1375 mL). The reaction mixture was heated to 40-50°C and stirred the mass at 40-50°C for 45 min. Water (1125 mL) was added at 40-50°C for 3-4 hrs, maintained for 8-10 hrs and then cooled the mass to room temperature. The obtained precipitated compound was filtered and washed with isopropyl alcohol. The same was repeated once again with the wet compound.

Dry weight: 82.3 g; Yield: 82.3%
Purity: 96% by HPLC.
Purification of 6-perdeoxy-6-per-chloro gamma cyclodextrin was also performed in a similar manner as described above to afford yield of 76.5%.

Example -4: Preparation of Sugammadex Sodium from 6-perdeoxy-6-per-bromo gamma cyclodextrin:

Lithium hydroxide (69.96 g, 1.66 eq.,) was taken into dimethylformamide (500 mL) under nitrogen atmosphere and the reaction mixture was cooled to 5°C. The solution of 3-mercaptopropionicacid (88.32 g, 0.80 eq.,) in dimethyl formamide was added at 5±5°C for 45 min. and stirred for 45 min at 5±5°C. 6-perdeoxy-6-per-bromo gamma cyclodextrin (100 g, 0.55 eq.,) in DMF was added at 5±5°C, heated the mass to 75°C, maintained for 2-6 hrs at 75-120°C under nitrogen atmosphere and then cooled to room temperature. Methanol (1000 mL) was added to the reaction mixture to get material precipitation. The obtained material was filtered and washed with methanol and dried at 55-65°C.

The above dried material was taken into water (600 mL) and then the pH of the reaction mass was adjusted to 11-13 with sodium hydroxide solution 25-35°C. The clear solution was treated with activated carbon (20 g) and filtered the carbon to obtain clear filtrate. Methanol (3000 mL) was added to the clear filtrate, stirred for 2 hrs. The obtained material was filtered under nitrogen atmosphere and washed with methanol (100 mL) and dried 50-55°C.
Dry weight: 102.3g; Yield: 84.6%

Example -5: Preparation of Sugammadex Sodium from 6-perdeoxy-6-per-bromo gamma cyclodextrin:
Title compound was prepared by using dimethyl sulfoxide (2000 mL) instead of dimethylformamide in a manner similar to that described for Example-5.
Yield of titled compound: 85.1%

Example -6: Preparation of Sugammadex Sodium
Title compound was prepared from 6-perdeoxy-6-per-chloro gamma cyclodextrin Lithium hydroxide (87.2 g, 2.07eq.,) instead of 6-perdeoxy-6-per-bromo gamma cyclodextrin and Lithium hydroxide (69.96 g, 1.66 eq.,) in a manner similar to that described for Example-5.
Yield of titled compound: 78.7%

Example -7: Preparation of Sugammadex Sodium from 6-perdeoxy-6-per-chloro gamma cyclodextrin
Title compound was prepared from 6-perdeoxy-6-per-chloro gamma cyclodextrin, Lithium hydroxide (87.2 g, 2.07eq.,) and dimethyl sulfoxide instead of 6-perdeoxy-6-per-bromo gamma cyclodextrin, Lithium hydroxide (69.96 g, 1.66 eq.,) and dimethylformamide in a manner similar to that described for Example-5.
Yield of titled compound: 69.3%

Example -8: Preparation of Di-Cesium salt of 3-mercapto propionic acid.
3-Mercapto propionic acid (100 g, 0.94 eq.,) was taken into tetrahydrofuran (1000 mL). Cesium carbonate (676.5g, 2.07 eq.) was added and then dissolved in water (100 mL) at 5-10°C under nitrogen atmosphere. The temperature of the reaction mixture was raised to 15°C and stirred for 1.0 hr at 15-20°C. Dimethyl formamide (500ml) was added to the reaction mixture at 15-20°C and stirred for 1 hour. The obtained precipitated compound was filtered and washed with the mixture of tetrahydrofuran and dimethyl formamide. The wet material was taken into mixture of tetrahydrofuran and dimethyl formamide, and stirred for 1 hr at 20-25°C under nitrogen atmosphere. The obtained material was filtered and dried under reduced pressure at 45-50°C for 8hours to get di-cesium salt of 3-mercaptopropionic acid
Dry Weight: 316.6 gm; Yield 91.0%.

Example-9: Preparation of Sugammadex sodium using Di-Cesium salt of 3-mercatopropionic acid
Di-cesium salt of 3-mercapto propionic acid (81.4 g, 0.22 eq.,) was taken in dimethyl sulfoxide (500 ml). The solution of 6-per-deoxy-6-bromo-gamma cyclodextrin (25 g, 0.0139 eq.,) in dimethyl sulfoxide (100 mL) was added under nitrogen atmosphere at 20-30°C. Then the reaction mixture was heated to 70-75°C, stirred for 5 hours under nitrogen atmosphere and cooled the mass to 30°C. The obtained material was filtered, washed with dimethyl sulfoxide (100mL) followed by ethanol (750 mL) and dried under vacuum at 40-50°C for 10 hours to yield Sugammadex Cesium.

Taken the above dried material into water (180 mL) at 20-25°C and stirred the reaction mixture for 15 minutes at room temperature. The solution of sodium hydroxide (4.5g sodium hydroxide in 4.5 mL water) and then Dimethyl sulfoxide (270 mL) were added to the reaction mass at same temperature. The obtained material was filtered, washed the wet cake with 10% aqueous dimethyl sulfoxide (100 mL), followed by ethanol (300 mL), and dried for 12 hours at 50-55°C.
Dry Weight: 24.5 g; Yield: 80.9%.

Example-10: Preparation of Sugammadex Cesium
Title compound was prepared by using Cesium carbonate (135.4g, 0.41 eq.,) and dimethyl sulfoxide instead of Lithium hydroxide (69.96 g, 1.66 eq.,) and dimethylformamide in a manner similar to that described for Example-5.
Yield of titled compound: 78.6%
Sugammadex Cesium prepared by using 6-per-deoxy-6-chloro-gamma cyclodextrin instead of 6-per-deoxy-6-bromo-gamma cyclodextrin in a similar manner as described above.

Example -11: Purification of Sugammadex sodium
Sugammadex sodium technical (50 g) was dissolved in water (150 mL) at room temperature under nitrogen atmosphere. The pH of the reaction mass was adjusted to 7.0-7.5 with dilute hydrochloric acid solution and the solution was treated with activated carbon (5.0 g). The reaction mixture was filtered to obtain clear filtrate and methanol (1650 mL) was added to the filtrate at 25-35°C and stirred for 2 hrs at 25-35°C. The obtained material was filtered, washed with methanol (100 mL) and dried at 55-65°C.
Dry weight: 41.0 g; Yield: 82%;
Purity: 98% by HPLC.
Example -13: Purification of Sugammadex sodium
Sugammadex sodium technical (50 g) was dissolved in water (150 mL) under nitrogen atmosphere at room temperature. The pH of the reaction mass was adjusted to 7.0-7.5 with dilute hydrochloric acid solution and the solution was treated with activated carbon (5g). The clear filtrate was heated to reflux, stirred for 30 min at reflux and slowly cooled to 50-60°C. Methanol (1650 mL) was added to the reaction mixture, cooled to room temperature and stirred for 1.0 hr. The obtained compound was filtered, washed with methanol and dried at 55-65°C.
Dry weight: 40 g; Yield: 80% ,CLAIMS:WE CLAIM:

1. A process for the preparation of Sugammadex sodium, which comprises:
a) reaction of 6-perdeoxy-6-per-halo-?-cyclodextrin:

Formula III
wherein X is halo is bromo, chloro or Iodo.

with 3-mercaptopropionic acid in presence of cesium salt to provide Sugammadex cesium; and

Formula II
wherein M is Cs or Li metal cation.

b) reaction of the Sugammadex cesium obtained from step a) with sodium base to provide Sugammadex sodium.

2. The process as claimed in claim 1, wherein the reaction of step a) comprises preparing Lithium or Cessium salt of 3-mercaptopropionic acid and reacting with 6-perdeoxy-6-per-halo-?-cyclodextrin.

3. The process as claimed in claim 2, wherein the salt of 3-mercaptopropionic acid is obtained by the reaction of 3-mercaptopropionic acid with lithium hydroxide or cesium salt.

4. The process as claimed in claim 1, wherein the cesium salt comprises cesium hydroxide, cesium sulfate, and cesium carbonate or cesium formate.

5. The process as claimed in claim 1, wherein the cesium salt comprises cesium carbonate.

6. The process as claimed in claim 1, wherein the reaction of step a) is carried out in presence of solvent.

7. The process as claimed in claim 6, wherein the solvent comprises dimethylformamide, dimethylsulfoxide, N-Methylpyrrolidine, Dimethylacetamide, 1,4-dioxane, tetrahydrofuran, 2-methyl tetrahydrofuran, chlorinated solvent, alcohol, ester, ketone or mixtures thereof.

8. A process for the purification of Sugammadex sodium, which comprises:
a) providing a solution of Sugammadex sodium in water;
b) treating the solution with HCl to adjust the pH 6-8;
c) refluxing the solution of step b); and
d) adding alcohol to the solution of step c) to obtain pure Sugammadex sodium.

9. The process as claimed in claim 8, wherein the Sugammadex sodium has a purity more than 95% by HPLC.

10. The process as claimed in claim 8, wherein the alcohol comprises methanol, ethanol, n-propanol, isopropanol, tert.butanol, n-butanol or mixtures thereof.