METHOD FOR THE PREPARATION OF PREGABALIN AND SALTS THEREOF
Related Applications
[0001] This application claims the benefit of U.S. Provisional Application Nos.
60/679,784, filed May 10,2005, and 60/689,699, filed June 9,2005, the contents of which are incorporated herein in their entirety by reference.
Field of the Invention
[0002] The present invention is directed to processes for preparing and purifying
Pregabalin and salts thereof.
Background of the Invention
[0003] (S)-Pregabalin, 3-(aminomethyl)-5-methyl-(3S)-hexanoic acid, which is also
known as (S)-(+)-3-(aminomethyl)-5-methylhexanoic acid, has the empirical formula
and a molecular weight of 159, and may be represented by the chemical structure:

(Formula Removed)

[0004] (S)-Pregabalin has been developed as a follow-up compound to Gabapentin,
NEURONTIN®, for use in the treatment of epilepsy, pain, anxiety, and social phobia. Both
(S)-Pregabalin and gabapentin are analogs of 4-aminobutyric acid (GABA), a
neurotransmitter that is thought to play a major inhibitory role in the central nervous system
(CNS). (S)-Pregabalin (PRG) has been approved in US for the treatment of nerve pain
associated with diabetes and shingles, as of December 31,2004. (S)-Pregabahn is available
as LYRICA™ in tablets for 25, 50, 75,150, 200, and 300 mg doses.
[0005] (S)-Pregabalin, which is also known as 7-amino butyric acid or (S)-3-isobutyl
GABA, has been found to activate GAD (L-glutamic acid decarboxylase), has a dose dependent protective effect on-seizure, and is a CNS-active compound. (S)-Pregabalin has been found to be useful in anticonvulsant therapy, due to its activation of GAD, promoting the production of GABA, one of the brain's major inhibitory neurotransmitters, which is released at 30 percent of the brains synapses. (S)-Pregabalin has analgesic, anticonvulsant, and anxiolytic activity.
[0006] The preparation of (S)-Pregabalin described in DRUGS OF THE FUTURE, 24 (8),
862-870 (1999) is done according to the following scheme:
(Scheme Removed)
wherein, (R)-(-)-3-(carbamoylmethyl)-5-methylhexanoic acid of formula 5, a key intermediate in the synthesis, is converted to (S)-Pregabalin via a Hoffmann degradation with Br2/NaOH, followed by precipitation of (S)-Pregabalin, after addition of HC1.
[0007] A very similar process is disclosed in U.S. Patent No. 5,616,793, wherein
(S)-Pregabalin is also obtained by the Hoffman degradation, followed by precipitation of (S)-Pregabalin, after addition of HC1. The product is further purified by crystallization from a mixture of isopropanol and water.
[0008] Hence, there is a need in the art for a process for the preparation and
purification of Pregabalin and salts thereof.
Summary of the Invention
[0009] In one embodiment, the present invention provides a process for the
preparation of Pregabalin comprising combining an alkali hydroxide and water; adding 3-(carbamoyhnethyl)-5-methylhexanoic acid (referred to as CMH) at a temperature of about 0°C to about 40°C; adding bromine, in a drop-wise manner, at a temperature of about 0°C to about 40°C; heating; reacting with a strong mineral acid; extracting with a C4-8 alcohol, and mixing with a base.
[00010] In a further embodiment, the present invention provides a process for the
preparation of Pregabalin comprising combining water and an alkali hydroxide selected from
a group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and cesium
hydroxide; adding CMH at a temperature of about 5°C to about 10°C; adding bromine, in a
drop-wise manner, at a temperature of about 5°C to about 10°C; heating to a temperature of
about 40°C to about 100°C; reacting with a strong mineral acid selected from a group
consisting of HaSO4, HC1, HBr and H3PO4; heating to a temperature of about 30°C to about
40°C, and mixing with a base selected from a group consisting of diisopropylamine,
dipropylamine, tributyl amine, triethyl amine, sodium hydroxide, potassium hydroxide,
cesium hydroxide, sodium carbonate, sodium bicarbonate and potassium carbonate.
[00011] In one embodiment, the present invention provides a process for the
preparation of the alkali salt of Pregabalin comprising combining an alkali hydroxide and water; adding CMH at a temperature of about 0°C to about 40°C; adding bromine, in a drop-/*/**wise manner, at a temperature of about 0°C to about 40°C, and heating; wherein the alkali salt of Pregabalin is, preferably, Pregabalin sodium.
[00012] In a further embodiment, the present invention provides a process for the
preparation of Pregabalin by preparing the alkali salt of Pregabalin, and converting it to Pregabalin.
Detailed Description of the Invention
[00013] As used herein, unless specified otherwise, the term "CMH" refers to either
the R enantiomer of CMH ((R)-CMH) or to the CMH racemate.

(Formula Removed)
[00014] As used herein, unless specified otherwise, the term "Pregabalin" refers to
either the S enantiomer of Pregabalin ((S)- Pregabalin) or to the Pregabalin racemate.
(Formula Removed)
[00015] As used herein, unless specified otherwise, when CMH racemate is used,
Pregabalin racemate is obtained.
[00016] As used herein, unless specified otherwise, when (R)-CMH is used,
(S)-Pregabalin is obtained.
[00017] As used herein, unless specified otherwise, the term "Pregabalin alkali salt"
refers to either the S enantiomer of Pregabalin alkali salt or to the racemate Pregabalin alkali
salt,

(Formula Removed)
(S)-Pregabalin alkali salt Pregabalin alkali salt
wherein M is an alkali metal.
[00018] The present invention relates to a process for preparing Pregabalin, wherein it
is obtained in high yields and purity. The process comprises maintaining at low temperatures the aqueous solution of the alkali hydroxide when combining with CMH, and when adding bromine, in a drop-wise manner. Hence, controlling the temperature during the additions, allows controlling the amount of impurities formed during the reaction. The process also includes purifying Pregabalin by preparation of its acidic salt, without isolating it, followed by selective extractions of the acidic salt of Pregabalin by the utilization of carefully chosen solvents and/or mixtures of solvents. Since a highly pure form, typically greater than 99.5 percent, of any drug is generally required for human treatment, a method that combines the control of the formation of impurities and a facile final purification is particularly advantageous.
The present invention provides a process for the preparation of Pregabalin comprising combining an alkali hydroxide and water; adding CMH at a temperature of about 0°C to about 40°C; adding bromine, in a drop-wise manner, at a temperature of about 0°C to about 40°C; heating; reacting with a strong mineral acid; extracting with a C4-8 alcohol, and mixing with a base.
[00020] Preferably, the preparation of Pregabalin may be done by combining water and
an alkali hydroxide is selected from a group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and cesium hydroxide; adding CMH at a temperature of about 5°C to about 10°C; adding bromine, in a drop-wise manner, at a temperature of about 5°C to about 10°C; heating to a temperature of about 40°C to about 100°C; reacting with a strong mineral acid selected from a group consisting of H2SO4, HC1, HBr and HsPO4; heating to a temperature of about 30°C to about 40°C, extracting with a C^g alcohol selected from a group consisting of butanol, iso-butanol, 2-butanol, pentanol and iso-pentanol, and mixing with a base selected from a group consisting of diisopropylamine, dipropylamine, tributyl amine, triethyl amine, sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium carbonate, sodium bicarbonate and potassium carbonate.
[00021] The present invention further provides a process for the preparation of
Pregabalin comprising combining water and an alkali hydroxide selected from a group
consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and cesium
hydroxide; adding CMH at a temperature of about 5°C to about 10°C; adding bromine, in a
drop-wise manner, at a temperature of about 5°C to about 10°C; heating to a temperature of
about 40°C to about 100°C; reacting with a strong mineral acid selected from a group
consisting of H2SO4, HC1, HBr and HsPO4; heating to a temperature of about 30°C to about
40°C, and mixing with a base selected from a group consisting of diisopropylamine,
dipropylamine, tributyl amine, triethyl amine, sodium hydroxide, potassium hydroxide,
cesium hydroxide, sodium carbonate, sodium bicarbonate and potassium carbonate.
[00022] The present invention also provides a process for the preparation of the alkali
salt of Pregabalin comprising combining an alkali hydroxide and water; adding CMH at a temperature of about 0°C to about 40°C; adding bromine, in a drop-wise manner, at a temperature of about 0°C to about 40°C, and heating; wherein the alkali salt of Pregabalin is, preferably, Pregabalin-sodium.
[00023] The present invention also provides a process for the preparation of Pregabalin
by preparing the alkali salt of Pregabalin, and converting it to Pregabalin.
[00024] Preferably, the alkali metal is selected from a group consisting of sodium,
potassium, lithium, and cesium. More preferably, the alkali metal is sodium.
[00025] Preferably, the alkali hydroxide is sodium hydroxide. Preferably, an aqueous
solution of the alkali hydroxide is used. Typically, the aqueous solution of the alkali
hydroxide is concentrated. Preferably, the concentration is of about 5 to about 20 molar, more
preferably of about 5 to about 10 molar. Typically, such solutions have a pH of at least about
13, preferably at least about 14.
[00026] Preferably, bromine is added in an amount of 1 mole equivalents to about 1.4
mole equivalents per mole equivalents of CMH. Preferably, the drop-wise addition is done
over a period of about 12 minutes to about 180 minutes, more preferably, of about 30 to
about 45 minutes.
[00027] Preferably, heating, after the addition of bromine, is done to a temperature of
about 60°C to about 85°C.
[00028] Preferably, heating, after the addition of bromine, is done for about 15 minutes
to about 4 hours, more preferably, for about 15 minutes to about an hour, prior to the addition
of the strong mineral acid.
[00029] Preferably, cooling to a temperature of about 40°C to about 20°C is done,
prior to the addition of the strong mineral acid.
[00030] Preferably, the strong mineral acid is H2SO4- Preferably, when adding the
strong mineral acid, a salt of Pregabalin with the strong mineral acid may be obtained.
Preferably, after adding the acid, heating to a temperature of about 30°C to about 35°C is
done. Preferably, a pH of less than about 3 is obtained when the strong mineral acid is added.
[00031] Preferably, the salt may be purified without isolating it. This salt is purified by
selective extractions with C4-8 alcohol. The extractions are selective due to the difference in
the solubility of the salt in water vs. the solubility of the impurities in water. Preferably, the
extractions with C4.8 alcohol are done, prior to the addition of the base. The preferred C4-8
alcohol is iso-butanol.
[00032] Preferably, the organic phase obtained from the extraction process is cooled to
a temperature of about 10°C to about 0°C, more preferably, to about 2°C, followed by
filtering off the inorganic salts obtained in the reaction. Preferably, the filtrate is combined
with a base, to obtain a precipitate of Pregabalin. Optionally, the organic phase may be
combined with the base without filtering the inorganic salts. Preferably, the base is either an
organic base or an inorganic base. The preferred organic base is either a secondary or tertiary
amine. Preferably, the secondary amine is either diisopropylamine or dipropylamine. More
preferably, the secondary amine is diisopropylamine. A preferred tertiary amine is either
tributyl amine or triethyl amine. More preferably, tertiary amine is tributyl amine. Preferably,
the inorganic base is either an alkali hydroxide or an alkali carbonate. A preferred alkali
hydroxide is sodium hydroxide, potassium hydroxide, lithium hydroxide, or cesium
hydroxide. More preferably, the alkali hydroxide is sodium hydroxide. A preferred alkali
carbonate is sodium carbonate, sodium bicarbonate, or potassium carbonate. More preferably,
the alkali carbonate is sodium carbonate. The more preferred inorganic base is alkali
carbonate, most preferably, sodium carbonate. The more preferred base is an organic base,
most preferably, a tertiary amine, and even most preferably, tributylamine.
[00033] When Pregabalin alkali salt is prepared, the heating step, after the addition of
bromine, further comprises stirring at a temperature of about 40°C to about 80°C, more
preferably, at about 50°C. Preferably, after stirring at about 50°C, cooling to a temperature of
about 10°C to about 0°C, more preferably, to about 0°C is done, to obtain a precipitate of the
salt, which is then recovered. Pregabalin alkali salt may be recovered by filtration, washing,
preferably, with water, and drying under vacuum, preferably at a temperature of about 45°C.
[00034] Preferably, the conversion of the alkali salt of Pregabalin to Pregabalin may be
done by mixing the salt; adding a strong mineral acid, and adding a base.
[00035] Preferably, mixing the alkali salt with a strong mineral acid provides the acidic
salt of Pregabalin, which is purified by extractions, as described before. After that, to the
organic phase is added a base, providing Pregabalin, also, as described before.
[00036] Having described the invention with reference to certain preferred
embodiments, other embodiments 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 describing in detail the preparation of the composition and methods of use of the invention. It will be apparent to those skilled in the art that many modifications, both to materials and methods, maybe practiced without departing from the scope of the invention.
EXAMPLES Example 1; Preparation of Pregabalin-Sodium (PRG-Na)
[00037] A 0.5 liter reactor was loaded with 160 ml of water and 58 g of NaOH. The
solution was cooled to from about 10° to about 15°C, and 40 g of CMH were added. The mixture was stirred, and 40 g of Bra were added drop-wise over a period of 45 minutes, while
maintaining the temperature at less than 20°C. The mixture was heated to 85°C for 15 minutes, stirred at 50°C for an hour, and cooled to 0°C. The Pregabalin-Na was filtered, washed with 40 ml of water, and dried at 45°C under vacuum, producing a 90 percent yield. Example 2; Preparation of Pregabalin from Pregabalin-Sodium
[00038] A 0.1 liter reactor was loaded with 12 ml of water and 7.5 g of Pregabalin-Na.
The mixture was stirred, and a 32 percent aqueous solution of HCI was added drop-wise to lower the pH to 0. The solution was then extracted with 25 ml of iso-butanol, the organic layer was separated, and tributyl amine, BuaN, was added in an amount sufficient to provide a pH of 4.6.- The mixture was then cooled to 0°C, and the resulting Pregabalin precipitate was filtered and dried at 55°C under vacuum, providing a 54 percent yield. Purity 98.6% Example 3: Preparation of Pregabalin from Pregabalin-Sodium
[00039] A 0.1 liter reactor was loaded with 12 ml of water and 7.5 g of Pregabalin-Na.
The mixture was stirred, and an aqueous 32 percent HCI solution was added drop-wise in an amount sufficient to lower the pH to 0. The solution was extracted with 25 ml of pentanol, the organic layer was separated, and BusN was added in an amount sufficient to provide a pH of 4.6. The mixture was then cooled to 0°C, and the Pregabalin precipitate was filtered and dried at 55°C under vacuum, providing a 72 percent yield. Purity 98 % Example 4; Preparation of Pregabalin
[00040] A 0.2 liter reactor was loaded with 60 ml of water and 17.65 g of NaOH. The
solution was cooled to from 10° to 15°C, and 15 g of CMH were added. Then, 15 g of Br2
were added drop-wise over a period of 15 minutes, while maintaining the temperature at less
than 20°C. The mixture was heated to 80°C for 15 minutes, and then cooled to room
temperature, i.e., about 20° to about 25°C. An aqueous 32 percent solution of HCI was added
in an amount sufficient to provide a pH of 1. The solution was then divided to two portions.
[00041] Portion I was extracted with 37 ml of iso-butanol, the organic layer was
separated, and Bu3N was added in an amount sufficient to provide a pH of 4. The Pregabalin
was precipitated, filtered, and washed with 10 ml of iso-butanol. After drying at 55°C under
vacuum, Pregabalin was obtained as white crystals in a 71 percent yield. Purity 97.2%
[00042] Portion II was extracted with 37 ml of pentanol, the organic layer was
separated, and Bu3N was added in an amount sufficient to provide a pH of 4. The Pregabalin was precipitated, filtered, and washed with 10 ml of pentanol. After drying at 55°C under vacuum, Pregabalin was obtained as white crystals in a 73 percent yield. Purity 93.1%
Example 5: Preparation of Pregabalin
[00043] A 0.1 liter reactor was loaded with 60 ml of water and 17.6 g of NaOH. The
solution was cooled to from 10° to 15°C, and 15 g of CMH were added. The mixture was
stirred, and 15 g of Bra were added drop-wise over a period of 45 minutes, while maintaining
the temperature at less than 20°C. The mixture was heated to 85°C for 15 minutes, and then
was cooled to about 20 to about 25°C. Then, 12.4 ml of H2SO4 were added drop-wise in an
amount sufficient to lower the pH to 1, and the resulting solution was divided to two portions.
[00044] Portion I was extracted with 37 ml of iso-butanol. The organic layer was
separated, and BuaN was added in an amount sufficient to provide a pH of 4, precipitation of
Pregabalin, which was filtered, and washed with 10 ml of iso-butanol. After drying at 55°C
under vacuum, Pregabalin was obtained as white crystals in a 63 percent yield. Purity 99.1%
[00045] Portion II was extracted with 37 ml of pentanol, the organic layer was
separated, and BuaN was added in an amount sufficient to provide a pH of 4. The precipitated Pregabalin was filtered, and washed with 10 ml of pentanol. After drying at 55°C under vacuum, Pregabalin was obtained as white crystals in a 61 percent yield. Purity 96.6% Example 6; Preparation of Pregabalin
[00046] A 0.2 liter reactor was loaded with 60 ml of water and 17.65 g of NaOH. The
resulting solution was cooled to from 10° to 15°C, and 15 g of CMH were added. Then, 15 g of Br2 were added drop-wise over 15 minutes, while maintaining the temperature at less than 20°C. The mixture was heated to 80°C for 15 minutes, and then cooled to room temperature, i.e., about 20 to about 25°C. Then, 75 ml of iso-butanol were added, and an aqueous 32 percent solution of HC1 was added in an amount sufficient to provide a pH of 2. The organic phase was separated, and Pregabalin was precipitated after the addition of 14 ml of Bu3N. The mixture was cooled to 2°C, and the solid was filtered, washed, and dried at 55°C under vacuum, providing a 61 percent yield. Purity 98.7% Example 7: Preparation of Pregabalin
[00047] A 0.2 liter reactor was loaded with 60 ml of water and 17.65 g of NaOH. The
solution was cooled to from 10° to 15°C, and 15 g of CMH were added. Then, 15 g of Br2 were added drop-wise over 15 minutes, while maintaining the temperature at less than 20°C. The mixture was heated to 80°C for 15 minutes, and then cooled to room temperature, i.e., about 20 to about 25°C. Then 75 ml of pentanol were added, followed by an aqueous 32 percent HC1 solution in an amount sufficient to provide a pH of 2. The organic phase was
separated, and Pregabalin was precipitated after the addition of 14 ml of Bu3N. The mixture was then cooled to 2°C, and the solid was filtered, washed, and dried at 55°C under vacuum, providing a 52 percent yield. Purity 96.9% Example 8; Preparation of Pregabalin
[00048] A 0.2 liter reactor was loaded with 110 ml of water and 27.65 g of NaOH.
The solution was cooled to from 10° to 15°C, and 23.5 g of CMH were added. Then, 23.5 g of Bra were added drop-wise over 15 minutes, while maintaining the temperature at less than 20°C. The mixture was heated to 80°C for 15 minutes, and then cooled to room temperature, i.e., about 20 to about 25°C. An aqueous 32 percent solution of HC1 was added in an amount sufficient to provide a pH of 2. The mixture was then extracted with 138 ml of iso-butanol, and the organic phase was separated. Pregabalin precipitated after the addition of diisopropylethyl amine in an amount sufficient to provide a pH of 4. The mixture was cooled to 2°C, and the solid was filtered, washed, and dried at 55°C under vacuum, providing a 43 percent yield. Purity 96.9%
Example 9: Preparation of Pregabalin
[00049] A reactor (1 L) was loaded with water (200 ml) and NaOH (34.7 g). The
solution was cooled to 5 °C and CMH (40 g) was added. Br2 (34.7 g) was added dropwise (15 min) while keeping the temperature below 10°C. The mixture was heated to 60° C for 15 min and then cooled to RT. Iso-butanol (120 ml) and then a solution of H2SO4 - 66% (40 ml) were added (pH=3). The mixture was heated to 33°C, then the phases were separated, and the aqueous phase was extracted with Iso-butanol (100 ml). The combined organic phases was cooled to 2°C for 2.5h, and filtered to remove inorganic salts. The filtrate was heated to room temperature, and Bu3N (41.6 g) was added to the organic phase. The mixture was heated to dissolution and then was cooled to 2°C, and stirred for 2h. The solid was filtered and the cake washed with i-BuOH (40 ml). A sample (3 g) was dried at 45 °C in a vacuum oven overnight. The weight loss was 32 %. This implies a calculated yield of 79.4%. Purity 99.5%. Example 10; Preparation of (S)-Pregabalin
[00050] A reactor (0.2L) was loaded with water (150 ml) and NaOH (32.3 g) to obtain
a solution. The solution was cooled to 5°C and (R)-CMH (30 g) was added. Br2 (25.9 g) was then added dropwise (15 min) while keeping the temperature below 10°C. The mixture was heated to 60°C for 15 minutes and then cooled to RT. Iso-butanol was added (90 ml) and then a solution of H2SO4 (66%) (32 ml).. The phases were separated, and the aqueous phase was extracted with Iso-butanol (75 ml). Bu3N (32.6 ml) was added to the combined organic
phases. The mixture was heated to dissolution and then was cooled to 2°C, and stirred for 1.5 hours. The solid was filtered, washed, and dried at 55°C under vacuum, providing an 80.4% yield. Total purity: 99.7% area by HPLC.
Example 11; Preparation of(S)Pregabalin
[00051] A reactor (0.1L) was loaded with water (50 ml) and NaOH (10.8 g) to obtain a
solution. The solution was cooled to 15 °C and (R)-CMH (10 g) was added. Br2 (8.6 g) was added dropwise (15 min) while keeping the temperature below 20°C. The mixture was heated to 60° C for 15 min and then cooled to RT. Iso-butanol (60 ml) and then a solution of H2SO4 (66%) (10 ml) were added. The phases were separated, and the aqueous phase was extracted with Iso-butanol (25 ml). To the combined organic phases BuaN (9.9 g) was added and the mixture was cooled to 2°C, and stirred for 2 hours. The solid was filtered, washed and dried at 55°C under vacuum, providing (S)-PREGABALIN with total purity 99.88% area by HPLC. Example 12: Preparation of (S)-Pregabalin
[00052] A reactor (0.5L) was loaded with water (165 ml) and NaOH (35.5 g) to obtain
a solution. The solution was cooled to 15 °C and (R)-CMH (33 g) was added. Br2 (28.51 g) was added dropwise (15 min) while keeping the temperature below 25°C. The mixture was heated to 60° C for 15 min and men cooled to 15°C. Iso-butanol was added (100 ml) and then a solution of HaSCU (66%) (33 ml) was added. The phases were separated, and the aqueous phase was extracted with Iso-butanol (83 ml). To the combined organic phases BusN (34.2 g) was added and the mixture was cooled to 2°C, and stirred for 2 hours. The solid was filtered, washed and dried at 55°C under vacuum, providing (S)-PREGABALIN with total purity 99.86% area by HPLC.

WE CLAIM:
1. A process for the preparation of Pregabalin comprising:
a) combining an alkali hydroxide and water;
b) adding CMH at a temperature of about 0°C to about 40°C;
c) adding bromine, in a drop-wise manner, at a temperature of about 0°C to about 40°C;
d) heating;
e) reacting with a strong mineral acid;
f) extracting with a C4-8 alcohol; and
g) mixing organic phase from step f with a base to obtain Pregabalin.
2. A process for the preparation of Pregabalin comprising:
a) combining water and an alkali hydroxide selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and cesium hydroxide;
b) adding CMH at a temperature of about 5°C to about 10°C;
c) adding bromine, in a drop-wise manner, at a temperature of about 5°C to about 10°C;
d) heating to a temperature of about 40°C to about 100°C;
e) reacting with a strong mineral acid selected from the group consisting of H2SO4, HC1, HBr and H3PO4;
f) heating to a temperature of about 30°C to about 40°C; and
g) mixing with a base selected from the group consisting of diisopropylamine, dipropylamine, tributyl amine, triethyl amine, sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium carbonate, sodium bicarbonate, and potassium carbonate, to obtain Pregabalin.
3. A process for the preparation of an alkali salt of Pregabalin comprising:
a) combining an alkali hydroxide and water;
b) adding CMH at a temperature of about 0°C to about 40°C;
c) adding bromine, in a drop-wise manner, at a temperature of about 0°C to about 40°C, and
d) heating.
4. The process as claimed in claim 3, wherein the alkali salt is selected from the group consisting of sodium, lithium, potassium, and cesium Pregabalin.
5. The process as claimed in claim 3, wherein the alkali salt is Pregabalin sodium.
6. The process as claimed in claim 3, further comprising converting the alkali salt of Pregabalin to Pregabalin.
7. The process as claimed in claim 6, wherein the conversion of the alkali salt of Pregabalin to Pregabalin is done by mixing the alkali salt of Pregabalin with a strong mineral acid, and adding a base.
8. The process as claimed in any of the claims 1 and 3, wherein the alkali hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, and cesium hydroxide.
9. The process as claimed in any of the claims 2 and 8, wherein the alkali hydroxide is sodium hydroxide.
10. The process as claimed in claim 9, wherein the alkali hydroxide is in a form of an aqueous solution.
11. The process as claimed in claim 10, wherein the concentration of the aqueous solution is about 5 to about 20 molar.
12. The process as claimed in any of the claims 1 and 3, wherein CMH is added, in step b, at a temperature of about 5°C to about 10°C.
13. The process as claimed in any of the claims 1 and 3, wherein bromine is added, in step c, at a temperature of about 5°C to about 10°C.
14. The process as claimed in any of the claims 1 to 3, wherein bromine is added in an amount of 1 mole equivalents to about 1.4 mole equivalents per mole equivalents of CMH.
15. The process as claimed in any of the claims 1 to 3, wherein the drop-wise addition, in step c, is done over a period of about 12 minutes to about 180 minutes.
16. The process as claimed in any of the claims 1 and 3, wherein heating, in step d, is done to a temperature of about 40°C to about 100°C.
17. The process as claimed in any of the claims 2 and 16, wherein, heating, in step d, is done to a temperature of about 60°C to about 85 °C.
18. The process as claimed in any of the claims 1 to 3, wherein the heating, in step d, is done for about 15 minutes to about 4 hours.
19. The process as claimed any of the claims 1 and 2, further comprising cooling to a temperature of about 40°C to about 20°C prior to step e.
20. The process as claimed in any of the claims 1 and 7, wherein the strong mineral acid is selected from the group consisting of H2SO4, HO, HBr, and H3PO4.
21. The process as claimed in any of the claims 2 and 20, wherein the strong mineral acid is H2SO4.
22. The process as claimed in any of the claims 1, 2, and 7, wherein a pH of less than about 3 is obtained when the strong mineral acid is added.
23. The process as claimed in claim 2, wherein heating, in step f, is done to a temperature of about 30°C to about 35°C.
24. The process as claimed in any of the claims 2 and 7, further comprising extracting with C4-8 alcohol prior to step g.
25. The process as claimed in any of the claims 1 and 24, wherein the C4-8 alcohol is selected from the group consisting of butanol, iso-butanol, 2-butanol, pentanol, and iso-pentanol.
26. The process as claimed in claim 25, wherein the C4-8 alcohol is iso-butanol.
27. The process as claimed in any of the claims 1 and 2, further comprising cooling to a temperature of about 10°C to about 0°C, and filtering off the inorganic salts, prior to mixing with the base.
28. The process as claimed in any of the claims 1 and 7, wherein the base is an organic base.
29. The process as claimed in claim 28, wherein the organic base is either a secondary or tertiary amine.
30. The process as claimed in claim 29, wherein the secondary amine is either diisopropylamine or dipropylamine.
31. The process as claimed in claim 30, wherein the secondary amine is diisopropylamine.
32. The process as claimed in claim 29, wherein the tertiary amine is either tributylamine or triethylamine.
33. The process as claimed in claim 32, wherein the tertiary amine is tributylamine.
34. The process as claimed in any of the claims 1 and 7, wherein the base is an inorganic base.
35. The process as claimed in claim 34, wherein the inorganic base is either an alkali hydroxide or an alkali carbonate.
36. The process as claimed in claim 35, wherein the alkali hydroxide is sodium hydroxide, potassium hydroxide, lithium hydroxide, or cesium hydroxide.
37. The process as claimed in claim 36, wherein the alkali hydroxide is sodium hydroxide.
38. The process as claimed in claim 35, wherein the alkali carbonate is sodium carbonate, sodium bicarbonate, or potassium carbonate.
39. The process as claimed in claim 38, wherein the alkali carbonate is sodium carbonate.
40. The process as claimed in any of the claims 1, 2, and 7, wherein the base is tributylamine.
41. The process as claimed in claim 3, wherein step d further comprises stirring at a temperature of about 40°C to about 80°C.
42. The process as claimed in claim 3, further comprising cooling to a temperature of about 10°C to about 0°C, after step d, to obtain a precipitate of the salt.
43. The process as claimed in any of the claims 1 to 42, wherein CMH is R-CMH.
44. The process as claimed in any of the claims 1 to 42, wherein Pregabalin is (S)-Pregabalin.