US 7902380, Levetiracetam

US 7902380,  Levetiracetam

http://www.google.im/patents/US7902380

preparation of both the (S)— and (R)-enantiomers of alpha-ethyl-2-oxo-1-pyrrolidineacetamide of formula 1 from (RS)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid of formula 2.

The following is an exemplary scheme of the process:

Suitable resolving agents include optically pure bases such as alpha-methylbenzylamine and dehydroabietylamine, of which alpha-methylbenzylamine is preferred. (S)-2 can be prepared by forming the salt with (R)-alpha-methylbenzylamine and the (R)-2 can be prepared by forming the salt with (S)-alpha-methylbenzylamine.
NOTE......R)-alpha-methylbenzylamine  is desired agent to get levetiracetam

The optical resolution of 2 may be carried out by, for example, the formation of a salt of (S)-2 with the optically active base (R)-alpha-methylbenzylamine or dehydroabietylamine (S. H. Wilen et al. Tetrahedron, 33, (1997), 2725-2736). Likewise, the (R)-2 can be prepared by forming the salt with (S)-alpha-methylbenzylamine. The racemic (RS)-2 used as starting material can be prepared by the known procedure described in GB 1309692.

Surprisingly we have found that the undesired (R) or (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid or their mixture can be epimerized by treating it with an acid anhydride, preferably acetic anhydride, propionic anhydride and butyric anhydride, to furnish a mixture of (R) and (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid in excellent yield. The recovered (RS)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid can be optically resolved by the same procedure above. In this way, we are able to obtain almost complete conversion of the (RS)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid to the desired (R) or (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid.

The process is depicted below:

EXAMPLE 1 
Preparation of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide from (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid

A suspension of (s)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid (45 g, 0.26 mol) in methylene chloride (225 ml) was cooled to 0° C. and triethylamine (53 g, 0.53 mol) and methanesulfonyl chloride (39 g, 0.34 mol) were added dropwise. The mixture was stirred at 0° C. for 30 min., then a stream of ammonia was purged in the solution for 2 hours. The insoluble solids were filtered and the filtrate was concentrated. The product was crystallized from methyl isobutyl ketone to give 36 g (80%) of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide.

EXAMPLE 2 
Preparation of (R)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide from (R)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid

A suspension of (R)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid (35 g, 0.20 mol) in methylene chloride (225 ml) was cooled to 0° C. and triethylamine (41 g, 0.40 mol) and methanesulfonyl chloride (29 g, 0.26 mol) were added dropwise. The mixture was stirred at 0° C. for 30 min., then a stream of ammonia was purged in the solution at 0° C. for 2 hours. The insoluble solids were filtered and the filtrate was concentrated. The product was recrystallized from methyl isobutyl ketone to give 27.5 g (78%) of (R)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide.

EXAMPLE 3 
Preparation of (S)-alpha-Ethyl-2-oxo-1-pyrrolidineacetic acid (R)-alpha-methylbenzylamine salt

A solution of (R)-alpha-methylbenzylamine (106 g) and triethylamine (89 g) in toluene (100 ml) was added to a suspension of (RS)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid (300 g, 1.75 mol) in toluene (1 L). The mixture was heated until complete dissolution, cooled to room temperature and stirred for 3 hours. The solids were filtered and rinsed with toluene (300 ml) to give 250 g of (s)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid (R)-alpha-methylbenzylamine salt. The solids were crystallized from toluene and 205 g (yield 41%) of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid (R)-alpha-methylbenzylamine salt was obtained. The isolated solid was treated with hydrochloric acid solution and the enantiomerically pure (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid could be isolated in 90% yield.

EXAMPLE 4 
Recovery and Epimerization of (R)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid from the Mother Liquor

The combined mother liquors from above were concentrated to half volume and water (200 ml) and 50% sodium hydroxide (52 g) were added sequentially and the mixture was stirred at 20° C. for 30 min. and then was separated. The aqueous layer was washed with toluene (150 ml), acidified with 32% hydrochloric acid until pH=2-3. The resulting suspension was cooled to 0-5° C. and stirred for 2 h. The solids were collected by filtration, and were rinsed with cold water. The damp solids were dried under vacuum oven at 40-50° C. for 4 h to give 160 g of (R)-enriched ethyl-2-oxo-1-pyrrolidineacetic acid. To the above solids, toluene (640 ml) and acetic anhydride (145 g) were added and the mixture was heated to reflux for 10 h. The solution was cooled to 20° C. and stirred for another 2 h. The solids were collected by filtration and rinsed with toluene (150 ml) to give (RS)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid (152 g).

extras

 (R)-(+)-alpha-methyl-benzylamine

Levetiracetam industrial process

2 pyrolidinone

ethyl 2 bromo butyrate

 (R)-(+)-alpha-methyl-benzylamine

ethyl chloro formate

US4943639.

http://www.google.co.in/patents/US4943639

cut paste

note………….racemic (±)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid is obt by rxn of 2 pyrolidinone with ethyl 2 bromo acetate

+/-)-(R,S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid methyl ester. CAS# 33978-83-5

EXAMPLE 1 (a) Preparation of the (R)-alpha-methyl-benzylamine salt of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid

8.7 kg (50.8 moles) of racemic (±)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid are suspended in 21.5 liters of anhydrous benzene in a 50 liter reactor. To this suspension is added gradually a solution containing 3.08 kg (25.45 moles) of (R)-(+)-alpha-methyl-benzylamine and 2.575 kg (25.49 moles) of triethylamine in 2.4 liters of anhydrous benzene. This mixture is then heated to reflux temperature until complete dissolution It is then cooled and allowed to crystallize for a few hours. 5.73 kg of the (R)-alpha-methyl-benzylamine salt of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid are thus obtained.

Melting point: 148°-151° C. Yield: 77.1%.

This salt may be purified by heating under reflux in 48.3 liters of benzene for 4 hours. The mixture is cooled and filtered to obtain 5.040 kg of the desired salt. Melting point: 152°-153.5° C. Yield: 67.85%.

(b) Preparation of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid

5.04 kg of the salt obtained in (a) above are dissolved in 9 liters of water. 710 g of a 30% sodium hydroxide solution are added slowly so that the pH of the solution reaches 12.6 and the temperature does not exceed 25° C. The solution is stirred for a further 20 minutes and the alpha-methylbenzylamine liberated is extracted repeatedly with a total volume of 18 liters of benzene.

The aqueous phase is then acidified to a pH of 1.1 by adding 3.2 liters of 6N hydrochloric acid. The precipitate formed is filtered off, washed with water and dried.

The filtrate is extracted repeatedly with a total volume of 50 liters of dichloromethane. The organic phase is dried over sodium sulfate and filtered and evaporated to dryness under reduced pressure.

The residue obtained after the evaporation and the precipitate isolate previously, are dissolved together in 14 liters of hot dichloromethane. The dichloromethane is distilled and replaced at the distillation rate, by 14 liters of toluene from which the product crystallizes.

The mixture is cooled to ambient temperature and the crystals are filtered off to obtain 2.78 kg of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid.

Melting point: 125.9° C. [alpha]D 20 =-26.4° (c=1, acetone). Yield: 94.5%.

(c) Preparation of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide

34.2 g (0.2 mole) of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid are suspended in 225 ml of dichloromethane cooled to -30° C. 24.3 g (0.24 mole) of triethylamine are added dropwise over 15 minutes. The reaction mixture is then cooled to -40° C. and 24.3 g (0.224 mole) of ethyl chloroformate are added over 12 minutes. Thereafter, a stream of ammonia is passed through the mixture for 41/2 hours. The reaction mixture is then allowed to return to ambient temperature and the ammonium salts formed are removed by filtration and washed with dichloromethane. The solvent is distilled off under reduced pressure. The solid residue thus obtained is dispersed in 55 ml toluene and the dispersion is stirred for 30 minutes and then filtered. The product is recrystallized from 280 ml of ethyl acetate in the presence of 9 g of 0,4 nm molecular sieve in powder form.

24.6 g of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide are obtained.

Melting point: 115°-118° C. [alpha]D 25 =-89.7° (c=1, acetone). Yield: 72.3%.

Analysis for C8 H14 N2 O2 in % calculated: C 56.45. H 8.29. N 16.46. found: 56.71. 8.22. 16.48.

The racemic (±)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid used in this synthesis has been prepared in the manner described below.

A solution containing 788 g (19.7 moles) of sodium hydroxide in 4.35 liters of water is introduced over 2 hours into a 20 liter flask containing 3.65 kg (18.34 moles) of ethyl (±)-alpha-ethyl-2-oxo-1-pyrrolidineacetate at a temperature not exceeding 60° C. When this addition is complete, the temperature of the mixture is raised to 80° C. and the alcohol formed is distilled off until the temperature of the reaction mixture reaches 100° C.

The reaction mixture is then cooled to 0° C. and 1.66 liter (19.8 moles) of 12N hydrochloric acid is added over two and a half hours. The precipitate formed is filtered off, washed with 2 liters of toluene and recrystallized from isopropyl alcohol. 2.447 kg of racemic (±)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid, melting at 155°-156° C., are thus obtained. Yield: 78%.

Analysis for C8 H13 NO3, in % calculated: C 56.12. H 7.65. N 8.18. found: 55.82. 8.10. 7.97.

EXAMPLE 2 (a) Preparation of ethyl (S)-4-[[1-(aminocarbonyl)propyl]amino]butyrate

143.6 ml (1.035 mole) of triethylamine are added to a suspension of 47.75 g (0.345 mole) of (S)-2-amino-butanamide hydrochloride ([alpha]D 25 : +26.1°; c=1, methanol) in 400 ml of toluene. The mixture is heated to 80° and 67.2 g (0.345 mole) of ethyl 4-bromobutyrate are introduced dropwise.

The reaction mixture is maintained at 80° C. for 10 hours and then filtered hot to remove the triethylamine salts. The filtrate is then evaporated under reduced pressure and 59 g of an oily residue consisting essentially of the monoalkylation product but containing also a small amount of dialkylated derivative are obtained.

The product obtained in the crude state has been used as such, without additional purification, in the preparation of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide by cyclization.

(b) Preparation of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide

54 g of the crude product obtained in a) above are dissolved in 125 ml of toluene in the presence of 2 g of 2-hydroxypyridine. The mixture is heated at 110° C. for 12 hours.

The insoluble matter is filtered off hot and the filtrate is then evaporated under reduced pressure.

The residue is purified by chromatography on a column of 1.1 kg of silica (column diameter: 5 cm; eluent: a mixture of ethyl acetate, methanok and concentrated ammonia solution in a proportion by volume of 85:12:3).

The product isolated is recrystallized from 50 ml of ethyl acetate to obtain 17.5 g of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide.

Melting point: 117° C. [alpha]D 25 : -90.0° (c=1, acetone). Yield: 41%.

EXAMPLE 3 (a) Preparation of (S)-N-[1(aminocarbonyl)propyl]-4-chlorobutanamide

345.6 g (2.5 moles) of ground potassium carbonate are mixed with 138.5 g (1 mole) of (S)-2-amino-butanamide hydrochloride in 2.5 liters of acetonitrile. The reaction mixture is cooled to 0° C. and a solution of 129.2 g (1.2 mole) of 4-chlorobutyryl chloride in 500 ml of acetonitrile is introduced dropwise. After the addition, the reaction mixture is allowed to return to ambient temperature; the insoluble matter is filtered off and the filtrate evaporated under reduced pressure. The crude residue obtained is stirred in 1.2 liter of anhydrous ether for 30 minutes at a temperature between 5° and 10° C. The precipitate is filtered off, washed twice with 225 ml of ether and dried in vacuo to obtain 162.7 g of (S)-N-[1-(aminocarbonyl)propy]-4-chlorobutanamide.

Melting point: 118°-123° C. [alpha]D 25 : -18° (c=1, methanol). Yield: 78.7%.

The crude product thus obtained is very suitable for the cyclization stage which follows. It can however be purified by stirring for one hour in anhydrous ethyl acetate.

Melting point: 120°-122° C. [alpha]D 25 : -22.2° (c=1, methanol).

(b) Preparation of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide

6.2 g (0.03 mole) of (S)-N-[1(aminocarbonyl)propyl]-4-chlorobutamine and 0.484 g (0.0015 mole) of tetrabutylammonium bromide are mixed in 45 ml of dichloromethane at 0° C. under a nitrogen atmosphere. 2.02 g (0.036 mole) of potassium hydroxide powder are added over 30 minutes, at such a rate that the temperature of the reaction mixture does not exceed +2° C. The mixture is then stirred for one hour, after which a further 0.1 g (0.0018 mole) of ground potassium hydroxide is added and stirring continued for 30 minutes at 0° C. The mixture is allowed to return to ambient temperature. The insoluble matter is filtered off and the filtrate is concentrated under reduced pressure. The residue obtained is recrystallized from 40 ml of ethyl acetate in the presence of 1.9 g of 0,4 nm molecular sieve. The latter is removed by hot filtration to give 3.10 g of (S)-alphaethyl-2-oxo-1-pyrrolidineacetamide.

Melting point: 116.7° C. [alpha]D 25 : -90.1° (c=1, acetone). Yield: 60.7%.

EXAMPLE 4 Preparation of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide……levetiracetam

This example illustrates a variant of the process of Example 3, in which the intermediate 4-chlorobutanamide obtained in situ is not isolated. 84 g of anhydrous sodium sulfate are added to a suspension of 69.25 g (0.5 mole) of (S)-2-amino-butanamide hydrochloride in 600 ml of dichloromethane at ambient temperature. The mixture is cooled to 0° C. and 115 g of ground potassium hydroxide are added, followed by 8.1 g (0.025 mole) of tetrabutylammonium bromide dissolved in 100 ml of dichloromethane. A solution of 77.5 g of 4-chlorobutyryl chloride in 100 ml of dichlorometha is added dropwise at 0° C., wih vigorous stirring. After 5 hours’ reaction, a further 29 g of ground potassium hydroxide are added. Two hours later, the reaction mixture is filtered over Hyflo-cel and the filtrate evaporated under reduced pressure. The residue (93.5 g) is dispersed in 130 ml of hot toluene for 45 minutes. The resultant mixture is filtered and the filtrate evaporated under reduced pressure. The residue (71.3 g) is dissolved hot in 380 ml of ethyl acetate to which 23 g of 0,4 nm molecular sieve in powder form are added. This mixture is heated to reflux temperature and filtered hot. After cooling the filtrate, the desired product crystallizes to give 63 g of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide.

Melting point: 117° C. [alpha]D 25 : -91.3° (c=1, acetone). Yield: 74.1%.

—

FROM MY OLD POST

(±)-(R,S)-alpha-ethyl-2- oxo-l-pyrrolidineacet-N-(+)-(R)-(l-phenylethyl)-amide a key levetiracetam intermediate

(±)-(R,S)-alpha-ethyl-2- oxo-l-pyrrolidineacet-N-(+)-(R)-(l-phenylethyl)-amide

methyl (±)-(R,S)-alpha-ethyl-2-oxo-l -pyrrolidine acetate with (+)-(R)-(l-phenylethyl)- amine in toluene in the presence of a base such as sodium hydride or methoxide; crystallization- induced dynamic resolution of the resultant (±)-(R,S)-alpha-ethyl-2- oxo-l-pyrrolidineacet-N-(+)-(R)-(l-phenylethyl)-amide

(R)-(+)-1-Phenylethylamine

33978-83-5
1-​Pyrrolidineacetic acid, α-​ethyl-​2-​oxo-​, methyl ester

1004767-60-5
1-​Pyrrolidineacetamide​, α-​ethyl-​2-​oxo-​N-​[(1R)​-​1-​phenylethyl]​-
(±)-(R.S)-alpha-ethyl-2-oxo-l-pyrrolidineacet-N-(+)-(R)-(l-phenylethyl)-amide

Example 1

(±)-(R,S)-alpha-ethyl-2-oxo-l-pyrrolidineacet-N-(+)-(R)-(l-phenylethyl)-amide.

In a 100 ml reactor equipped with mechanical stirring, thermometer and bubble condenser, 13.4 g of (±)-(R,S)-alpha-ethyl-2-oxo-l-pyrrolidineacetic acid methyl ester (71.6 mmol), 8.8 g of (+)-(R)-(l-phenylethyl)-amine (72.5 mmol) and 45 ml of tetrahydrofuran were charged. 3.4 g of NaH (60% dispersion in mineral oil, 85.6 mmol) was added in small portions under nitrogen atmosphere. Reaction mixture was maintained at room temperature for about 2 h. Then, it was heated up to 350C and kept under stirring overnight. Reaction was controlled by TLC (Rf = 0.5, AcOEt/silica gel).

At reaction completed, one night at 35°C temperature, reaction mixture was cooled to room temperature and 30 ml of water was slowly charged. It was transferred into a separatory funnel and was diluted with 30 ml of water and 80 ml of dichloromethane. Phases were separated and the aqueous one was washed with 50 ml of dichloromethane. Collected organic phases were washed with an aqueous acid solution, dried on Na2SO4, filtered and concentrated under vacuum. 19.5 g of an oil residue was obtained which slowly solidified. Solid was suspended in 20 ml of a hexane/dichloromethane 9/1 v/v mixture. It was then filtered, washed with 10 ml of the same solvent mixture and dried at 400C to give 12.1 g of the title compound (44.1 mmol, 61.6% yield) as dry solid.

1H NMR (400.13 MHz, CDCl3, 25 0C): δ (ppm, TMS)
7.35-7.19 (1OH, m),
6.49 (2H, br s),
5.09-5.00 (2H, m),
4.41 (IH, dd, J = 8.3, 7.4 Hz),
4.36 (IH, dd, J = 8.6, 7.1 Hz),
3.49 (IH, ddd, J = 9.8, 7.7, 6.6 Hz),
3.41 (IH, ddd, J = 9.8, 7.7, 6.2 Hz),
3.30 (IH, ddd, J = 9.6, 8.3, 5.5 Hz),
3.13 (IH, ddd, 9.7, 8.5, 6.1 Hz), 2.47-2.38 (2H, m), 2.41 (IH, ddd, J = 17.0, 9.6, 6.3 Hz), 2.26 (IH, ddd, 17.0, 9.5, 6.6 Hz), 2.10-1.98 (2H, m), 2.01-1.89 (IH, m), 1.99-1.88 (IH, m), 1.98-1.85 (IH, m), 1.88-1.78 (IH, m), 1.75- 1.62 (IH, m), 1.72-1.59 (IH, m), 1.45 (3H, d, J = 7.1 Hz), 1.44 (3H, d, J = 7.1 Hz), 0.90 (3H, t, J = 7.4 Hz), 0.86 (3H, t, J = 7.4 Hz).  

13C NMR (100.62 MHz, CDCl3, 25 0C): δ (ppm, TMS)
176.05 (CO), 176.00 (CO), 169.08 (CO),
168.81 (CO), 143.59 (Cquat),
143.02 (Cquat), 128.66 (2 x CH), 128.55 (2 x CH),
127.33 (CH), 127.19 (CH), 126.05 (2 x CH),
125.80 (2 x CH), 56.98 (CH), 56.61 (CH),
48.90 (CH), 48.84 (CH), 44.08 (CH2),
43.71 (CH2), 31.19 (CH2), 31.07 (CH2), 22.08 (CH3),
22.04 (CH3), 21.21 (CH2), 20.68 (CH2),
18.28 (CH2), 18.08 (CH2), 10.50 (CH3), 10.45 (CH3).

Example 2 (±)-(R.S)-alpha-ethyl-2-oxo-l-pyrrolidineacet-N-(+)-(R)-(l-phenylethyl)-amide (alternative 1).

In a 500 ml reactor equipped with mechanical stirring, thermometer and condenser, 24.2 g of (+)-(R)-(l-phenylethyl)-amine (199.51 mmol) and 40 ml of toluene were charged. By keeping the reaction mixture at 00C temperature under nitrogen atmosphere, 9.5 g of NaH (60% mineral oil suspension, 237.50 mmol) was added in small portions. At the same temperature, 190.0 g of a toluene solution of (±)-(R,S)- alpha-ethyl-2-oxo-l-pyrrolidineacetic acid methyl ester (19.28% equal to 36.63 g, 197.77 mmol) was charged. Reaction mixture was then heated up to 35°C and maintained in that condition till complete disappearing of methyl ester reagent (about 14 h; checked by HPLC).

At reaction completed, reaction mixture was cooled and when room temperature was reached, 100 ml of water was slowly charged. Aqueous phases were separated and extracted with toluene (2 x 75 ml). Collected organic phases were treated with acid water till neuter pH. Solvent was evaporated and residue was suspended in about 100 ml of heptane for about 30 minutes. Product was isolated by filtration and dried in oven at 400C temperature under vacuum overnight to give 45.2 g of the title compound (164.54 mmol, 83.2% yield, d.e. 0.0%) as white dusty solid.

Example 3

(±)-(R,S)-alpha-ethyl-2-oxo-l-pyrrolidineacet-N-(+)-(R)-(l-phenylethyl)-amide (alternative 2).

In a 500 ml reactor equipped with mechanical stirring, thermometer and Dean-Stark distiller, 24.2 g of (+)-(R)-(l-phenylethyl)-amine (199.51 mmol) and 40 ml of toluene were charged. By keeping the reaction mixture at 00C temperature, 42.7 g of sodium methoxide (30% solution in methanol, 237.14 mmol) was added under nitrogen atmosphere. At the same temperature, 190.0 g of a toluene solution of (±)- (R,S)-alpha-ethyl-2-oxo-l-pyrrolidineacetic acid methyl ester (19.28% equal to 36.63 g, 197.77 mmol) was charged. Reaction mixture was then heated up to 65- 700C and maintained in that condition till complete disappearing of methyl ester reagent (about 4 h; checked by HPLC). After a work-up carried out according to the procedure described in example 2, 40.2 g of the title compound (146.53 mmol, 74.1% yield, d.e. 0.0%) as white dusty solid was obtained.

http://www.google.com/patents/WO2008012268A1?cl=en

P.S. : The views expressed are my personal and in no-way suggest the views of the professional body or the company that I represent.

P.S. : The views expressed are my personal and in no-way suggest the views of the professional body or the company that I represent.

P.S. : The views expressed are my personal and in no-way suggest the views of the professional body or the company that I represent.

P.S. : The views expressed are my personal and in no-way suggest the views of the professional body or the company that I represent.

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Process for producing levetiracetam EP 1517893

Process for producing levetiracetam 
EP 1517893 A2 (text from WO2004069796A2) 



LEVETIRACETAM

(−)-(S)-α-ethyl-2-oxo-1-pyrrolidineacetamide




A process for preparing (S)- α-ethyl-2-oxo-l -pyrrolidineacetamide which comprises cyclizing (S)-N-[l-(aminocarbonyl)propyl]- 4-chlorobutanamide, in a solvent selected from the group consisting of acetonitrile and methyl tertbutyl ether, in the presence of a strong base, and recovering the crude levetiracetam.


(2S)-2-(4-chlorobutanoylamino)butanamide
 (S)-N-[l-(aminocarbonyl)propyl]- 4-chlorobutanamide

• 4-CHLOROBUTYRYL CHLORIDE     
• CAS No.: 4635-59-0
• Formula: C4H6Cl2O

Scheme 

A process for preparing (S)-α-ethyl-2-oxo-l -pyrrolidineacetamide (levetiracetam) comprising reacting (S)-2-amino-butanamide hydrochloride and 4-chlorobutryl chloride in a solvent selected from the group consisting of acetonitrile and methyl tertbutyl ether, in the presence of a strong base, and recovering the crude levetiracetam.

key intermediate

• CAS Number 7682-20-4
   
• Linear Formula CH₃CH₂CH(NH₂)CONH₂ · HCl
   
• Molecular Weight 138.60

(S)-(+)-2-Aminobutanamide hydrochloride

2S)-2-Aminobutanoic acid hydrochloride

Example 1

PREPARATION OF CRUDE LEVETIRACETAM FROM L-ABA HCL IN

ACN

Anhydrous sodium sulfate 13.6 g (0.096 M) is added to dry acetonitrile (ACN) (96 ml) under vigorous stirring at 3-5 degrees C. and under a nitrogen blanket. (S)-2- amino-butanamide hydrochloride (L-ABA HC1) 11.08g (0.08 M) is added. The mixture is stirred at 3-5 degrees C. for 30 minutes. Powdered KOH 17.23 g (0.28 M) is added. 4-chlorobutyryl chloride 12.41g (0.088M) in 39 ml dry acetonitrile is added drop-wise over a period of about 30 minutes, while the temperature is kept under 5 degrees C. The reaction mixture is stirred while the temperature is kept under 5 degrees C for a further 5 hrs. The insoluble matter is filtered off and washed with acetonitrile (15 ml). The filtrate and washing are evaporated in vacuo at 35-40 degrees C. The residue is recrystallized from 50 ml ethyl-acetate to give 9.6 g (Yield=70 %) of product displaying 99 % purity (crude product) by capillary GC; 99.65% L-isomer and 0.35 % D-isomer (D-Levetiracetam) by dextrine based chiral capillary GC.

The amount of D-isomer was determined as follows: Column: Beta Dex325 capillary column 30m x 0.25mm+0.25micron thickness. Oven: 160 degrees C; Carry gas: nitrogen, flow lml min.; Detector FID, 230 degrees C; Injection: split. 150:1, 210 degrees C; Sample: 1 microliter of 0.05% levitiracetam solution in methanol; RT of D-isomer: 34.5 min, levitiracetam-33.4 min.

Example 2

PREPARATION OF CRUDE LEVETIRACETAM FROM L-ABA HCL IN ACN USING A DRYING AGENT

L-ABA HC1 69.25 g (0.5 M) and powdered KOH 101.25 g (1.8 M) are added to a vigorously stirred suspension of powdered molecular sieves in 625 ml acetonitrile under nitrogen. The temperature is kept at about 10 degrees C. A solution of 4- chlorobutyryl chloride 77.5 g (0.5M) in acetonitrile 250 ml is added drop-wise. The temperature is kept under 20 degrees C. After 2 hrs, 1.25 liters of acetonitrile are added and the mixture is stirred for 1 hour and then filtered. The solid is washed with acetonitrile (25ml). The combined filtrate and washes are evaporated in vacuo to yield a semi-solid oil 70 g, which upon crystallization from warm ethyl-acetate (150) ml leads to 60.5.5 g (72 %) of levetiracetam 98.2 % purity (crude product).

Example 3 PREPARATION OF CRUDE LEVETIRACETAM FROM L-ABA HCL IN ACN WITH NEUTRALIZATION Anhydrous sodium sulfate 99.6 g is added with stirring into acetonitrile 700 ml under a nitrogen blanket. The temperature is set and maintained at 3-5 degrees during the reaction.

L-ABA HC1 69.25 g (0.5 M), followed by 124 g ground KOH are then introduced into the above mixed suspension. 4-chlorobutyryl chloride 77.6 g (0.55 M.) is added at a rate sufficient to keep the temperature at 3-5 degrees C. The reaction mixture is kept for 5 hrs under these conditions. The mixture is then neutralized with care to about pH 6 using concentrated HC1 (32%). The mixture is filtered and washed twice with acetonitrile (total 400 ml). The filtrate and washes are combined and concentrated to a 500 ml solution which is filtered. Upon cooling, crude levetiracetam crystallizes displaying about 99 % purity (HPLC). Recrystallization from warm ethyl acetate leads to 72 g (84 %) of pure levetiracetam, displaying >99.5% isomeric purity by chiral capillary GC.

Example 4

PREPARATION OF CRUDE LEVETIRACETAM FROM L-ABA HC1 IN MTBE 6.92 g (0.05 M) L-ABA HCL and 10.12 g (0.18 M) ground KOH and 7.53 g

(0.053M) of NaS0₄ are mixed vigorously in 62 ml methyl tert butyl ether (MTBE). The temperature is kept at 5 degrees C. A solution of 7.75 g (0.05 M) of 4- chlorobutyryl chloride (CBC) is added drop-wise. After 3 hours, the mixture is allowed to return to room temperature during 1 hour. The reaction mix is filtered and the solid is washed with a total of 87 ml MTBE to give a crude solid 6.5 g containing levetiracetam having a purity of 76% as per HPLC.

Example 5 PREPARATION OF (S)-N-[l-(aminocarbonyl)propyl]-4-chlorobutanamide (CBA) FROM ABA BASE IN MTBE

5.1 g (0.05 M) of ABA base and 9.75 g (0.1 M) of 2-hydroxypyridine are mixed vigorously in 60 ml of MTBE at 0-5 degrees C. A solution of 8.45 g (0.06 M) of CBC in 25 ml MTBE is added drop-wise over 30 minutes. The reaction is nearly completed after 2 hours but was left overnight for 17 hours. The reaction mix is filtered and the solid washed with 15 ml acetonitrile. The combined extracts are evaporated to a crude solid residue of 13 g which contains CBA having a purity of 91 % as per HPLC. Example 6

PREPARATION OF LEVETIRACETAM FROM CBA IN THE PRESENCE OF KI IN MTBE

6.2 g (0.03 M) of CBA 2.5 g of ground KOH and 0.33 g (0.002 M) KI catalyst are stirred in MTBE vigorously at room temperature. After 4 hours, the mixture is filtered and the solid is washed twice with hot ethyl acetate. HPLC of the crude mixture indicates a purity of 95.9 % of levetiracetam.

Example 7 (Comparative Example) PREPARATION OF LEVETIRACETAM FROM CBA IN MTBE WITHOUT KI

6.2 g (0.03 M) of CBA 2.5 g of ground KOH are stirred vigorously at room temperature in MTBE. After 4 hours, the reaction mixture is filtered and the solid is washed twice with hot ethyl acetate. HPLC of the crude mix indicates 88.6 % levetiracetam.

Example 8

PURIFICATION OF LEVETIRACETAM FROM VARIOUS SOLVENTS

Experimental Procedure:

A 100 ml flask is charged with 3 g of levetiracetam. Solvent is added in portions under slight reflux until total dissolution. Solutions are left to cool to room temperature for 5 hours and stored at

4 degrees C. for a further 16 hours. The crystalline material is filtered on buchner. The material is dried at 40-45 degrees C. under 100mm vacuum.

Example 9

PURIFICATION OF LEVETIRACETAM FROM A MIXTURE OF TWO SOLVENTS

Experimental procedure: A 100 ml flask is charged with 3 g. levetiracetam and the selected solvent is added in portions at about 40 degrees C, under stirring. The co-solvent is then added in portions until the solution is turbid. The suspension is left to cool under stirring to room temperature for 5 hours and left at 4 degrees C. for a further 16 hours. The crystalline material is filtered on buchner. The material is dried at 40-45 degrees C. l der 100mm vacuum.

Example 10 PREPARATION OF LEVETIRACETAM FROM L-ABA HCL IN ACN USING A DRYING AGENT

27.7 g (0.2 M ) ABA HC1 is added to 80 g (0.56 M) powdered K₂CO₃ in 500 ml ACN and the mixture is stirred at room temperature for 30 minutes and then cooled to about 0 degrees Celcius. A solution of 4-chlorobutyryl chloride, 31 g (0.22 M ) in 100 ml of ACN is added to the mixture over a period of about 1 hour while the temperature is kept at between about 0-3 degrees Celcius. The reaction mixture is brought to room temperature and stirred for 2 hours. The temperature of the reaction mixture is raised to 30 degrees Celcius and 8.4 g (0.21 M) sodium hydroxide is added. After 90 minutes, another charge of 8.4 g sodium hydroxide is introduced and the mixture is stirred at 30 degrees Celcius for another 150 minutes. The suspension is filtered and the solid is washed with 0.25 liters of ACN. The filtrate and washes are combined and evaporated in vacuo to a solid which is crystallized from about 80 ml of hot ACN leading to a crude 26 g Levetiracetam (77 % purity). Recrystallization of the crude levetiracetam from 170 ml hot ethylacetate gives 23.5 g of the final product.

Publication number	EP1517893 A2
Publication type	Application
Application number	EP20040707805
PCT number	PCT/US2004/003149
Publication date	30 Mar 2005
Filing date	3 Feb 2004
Priority date	3 Feb 2003
Also published as	CA2515090A1, 6 More »
Inventors	Ben-Zion Dolitzky, Serguel Finogueev, Jean Hildesheim
Applicant	Teva Pharmaceutical Industries Limited
Export Citation	BiBTeX, EndNote, RefMan
Non-Patent Citations (1), Classifications (6), Legal Events (6)
External Links: Espacenet, EP Register

.............................................

http://www.google.com/patents/WO2008077035A2?cl=en

Levetiracetam is chemically known as (-)-(S)-α-ethyl-2-oxo-1 -pyrrolidine acetamide. It is represented by the Formula I:

Formula I

Levetiracetam is an antiepileptic drug useful for the treatment of epilepsy and is available in the market under the brand name "KEPPRA" in the form of tablet, oral solution and injection.

Gobert et. al. in U.S. Patent No. 4,943,639 disclose levetiracetam, its homologues and pharmaceutical composition thereof. The '639 patent also discloses a process for the preparation of levetiracetam, which is summarized in scheme 1 :

Scheme 1 : Process for preparing levetiracetam per USP 4,943,639

Acharyulu et al., in US 2005182262, describe a process for the preparation of levetiracetam, which is summarized in scheme 2:

Scheme 2: Process for preparing levetiracetam as per US 2005182262

Futagawa et al., in US 6,107,492, disclose a method of resolution of racemic mixture of alpha-ethyl-2-oxo-1-pyrrolidineacetamide through chromatography column packed with optical resolution packing material, that contains silica gel-supported amylose tris (3,5-dimethylphenyl carbamate).

WO 2006/095362 describes a process for the preparation of levetiracetam, which is summarized in scheme 3:

Scheme 3: Process for preparing levetiracetam per WO '362

WO 2006/053441 discloses a process for the preparation of levetiracetam by reacting (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid with methane sulfonyl chloride and a stream of ammonia in the presence of triethyl amine.

WO 2006/127300 describes a process for the preparation of levetiracetam by reacting (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetic acid with ditertiary butyl dicarbonate and ammonium bicarbonate in the presence of acetonitrile and pyridine.

Although various processes for preparation of levetiracetam are disclosed in the art, they may suffer from one or more drawbacks. Hence, there is a continuing need for a commercially viable process for preparing levetiracetam. SUMMARY

In one embodiment, there is provided a process for preparing levetiracetam:

(I) via a reaction between S-aminobutyramide or its salt:

and 4-chlorobutyrylchloride:

which process includes forming a reaction mixture from the S-aminobutyramide or its salt, the 4-chlorobutyrylchloride, and potassium hydroxide, wherein the potassium hydroxide is added to the reaction mixture in a lot-wise manner. Various variants are provided.

EXAMPLE-8: PREPARATION OF (-)-(S)-α-ETHYL-2-OXO-1 -PYRROLIDINE ACETAMIDE (FORMULA I)..

LEVETIRACETAM

 S-aminobutyramide hydrochloride (60 g) and dichloromethane (720 ml) were charged into a clean dry round bottom flask and stirred at a temperature of about -10°C for about 10 minutes. Tetra-butyl ammonium bromide (27.8 g) was added and stirred at -10°C for about 10 minutes. Potassium hydroxide (48.5 g) was added at about -10°C and stirred for about 15 minutes followed by addition of mixture of 4-chloro butyrlchloride (30.5 g) and dichloromethane (60 ml) was added slowly at a temperature of about -6⁰C over a period of about 45 minutes. The resultant reaction mixture was stirred for about 45 minutes. Potassium hydroxide (48.5 g) was added at about -10°C and stirred for about 15 minutes followed by addition of 4-chlorobutyrl chloride (18.4 g) and dichloromethane (60 ml) slowly over about 30 minutes and stirred for about 45 minutes. A lot of potassium hydroxide (24.2 g) was added at a temperature of about -1O⁰C and stirred for about 15 minutes followed by the addition of 4-chlorobutyrl chloride (18.4 g of) dissolved in dichloromethane (60 ml) over a period of about 30 minutes. The restιltantH^r€aεtionHmxture^/vas stirred at a temperature of about -2°C for about 5 hours. Potassium hydroxide (12.1 g) was added followed by stirring for about 2 hours. pH of the reaction mixture was adjusted to about 7 to about 7.5 by addition of acetic acid (45 ml). The unwanted solid was filtered and the solid was washed with dichloromethane (120 ml). The organic layer was dried over anhydrous sodium sulphate (60 g). The obtained clear organic layer was distilled off completely at about 35°C under vacuum. Ethyl acetate (60 X 2 ml) was added to the residue and distilled completely under vacuum to remove the traces dichloromethane, yielding the title compound as a solid residue. To the obtained residue ethyl acetate (120 ml) was added at a temperature of about 25⁰C to about 30⁰C and stirred for about 30 minutes. The reaction mixture was cooled to a temperature of about O⁰C followed by stirring for about 30 minutes. The separated solid was filtered and the solid was washed with precooled ethyl acetate (24 ml). The obtained solid was dried at about 40°C under vacuum for about 3 hours to afford 70.5 g of pure title compound. Yield: 95.68% Purity by HPLC: 99.15%. Purity by chiral HPLC: 99.8%.

EXAMPLE-7: PREPARATION OF (-)-(S)-α-ETHYL-2-OXO-1 -PYRROLIDINE ACETAMIDE AS PER US 4,943,639

Sodium sulfate (25 g) was added to a suspension of (S)-2-amino- butanamide hydrochloride (20 g) in dichloromethane (175 ml) at a temperature of about 25 to about 35°C. The reaction mixture was cooled to about O⁰C to about - 1O⁰C followed by the addition of potassium hydroxide (33.1 g) and tetra butylammonium bromide (2.3 g). A solution of 4-chlorobutyrylchloride (22.3 g) in dichloromethane (30 ml) was added to the reaction mixture over a period of 1 hour and stirred for about 2 hours. Potassium hydroxide (8.3 g) was added to the reaction mixture and stirred for about 5 hours 30 minutes. The reaction mixture was filtered and washed with dichloromethane (50 ml). The filtrate was concentrated completely followed by the addition of toluene and then distilled off the solvent completely. Ethylacetate (110 ml) was added to the reaction crude and heating given to a temperature of about 75 to about 80⁰C and stirred for about 20 minutes. Filtered the suspension and washed the solid with ethylacetate (10 ml). The obtained filtrate was distilled completely followed by ethylacetate (80 ml) was added and then stirred for about 15 minutes. The reaction suspension was cooled to about 0°C to about 5°C and stirred for about 1 hour 45 minutes. Acetone (10 ml) was added to the reaction mixture and stirred for about 1 hour 40 minutes. The sususpension was filtered and dried the solid at a temperature of about 60⁰C for about 3 hours 30 minutes to afford 8.5 g of title compound. Purity: 96.7% by HPLC; Yield: 34.61% 16.1% of (S)-2-amino-butanamide hydrochloride, 65% of 4-chlorobutyrylchloride and 7.2% of intermediate of Formula A were not converted to title compound.

..........................
PATENT

US 2005182262

http://www.google.com/patents/US20050182262

EXAMPLE 1
(S)-2-aminobutyramide hydrochloride

The compound (S)-2-aminobutyramide hydrochloride is prepared by dissolving 50 grams of (S)-2-aminobutyric acid hydrochloride in 100 mL of methanol, and adding 28.7 mL of thionyl chloride while maintaining the reaction mixture temperature below about 55° C., then stirring until the reaction is complete. A vacuum is applied and maintained until the methanol has been distilled from the mixture. Isopropanol is then added, followed by the introduction of ammonia gas at a pressure about 60 psi (413 kPa) until the reaction is complete. After filtering to remove formed ammonium chloride, the solvent is partially evaporated and isopropanol hydrochloride is added. The mixture is stirred while solid product forms, then the solid is separated by filtration and washed with isopropanol.

The product was characterized by the following ¹H NMR data (200 MHz, DMSO-d₆): 0.9-1.0(t,3H), 1.8-1.9(Q,2H), 3.7-3.8(t, 1H), 7.5-7.7(Br,NH₂), 8.0-8.2(Br,NH₂)

EXAMPLE 5

The compound (−)-(S)-α-ethyl-2-oxo-1-pyrrolidineacetamide is prepared by suspending 50 grams of (S)-2-aminobutyramide hydrochloride in 500 mL of dichloromethane at room temperature, then cooling to temperatures between −5 and 0° C. and adding 81.2 grams of potassium hydroxide and 23.3 grams of tetrabutylammonium bromide at those temperatures. A 66.4 gram amount of 4-chlorobutyryl chloride is added at the same temperatures. After completion of the reaction, solids are removed by filtration, the solution is adjusted to pH 7-7.5 with acetic acid, and dichloromethane is partially evaporated by the application of a vacuum. 150 mL of ethyl acetate are added to precipitate the product, which is isolated by filtration and washed with ethyl acetate and then with acetone; the product has a chiral purity of 99.8 percent by high performance liquid chromatography. The final product is purified by recrystallization from ethyl acetate, giving a yield of 60-65 percent.LEVETIRACETAM

..............................................

PATENT

ROUTE FROM D-(+)-2-amino butanol 

http://www.google.im/patents/WO2006095362A1?cl=en

WO 2006/095362 

describes a process for the preparation of levetiracetam, which is summarized in scheme 3:

 Thus according to one aspect the present invention relates to a process for the preparation of (S)-(-)-α~ethyl-2-oxo-l-pyrrolidineacetamide of Formula (I), comprising the steps of :

i) condensation of (S)-2-amino butanol of Formula (IΙ)and 4-halobutryl chloride, where halo group can be chloro, bromo or iodo in solvents to form α-ethyl-2-oxo pyrrolidine ethanol of Formula (III)

................(H) ...........................................................................(III)

ii) oxidation of (S)-α-ethyl-2-oxo pyrrolidine ethanol to yield (S)-α-ethyl-2-oxo pyrrolidine acetic acid having the formula (IV)

(IV)

iii) esterification of (S)-α-ethyl-2-oxo pyrrolidine acetic acid (IV) with an alcohol to provide alkyl ester of Formula (V) wherein, R is 1-4 Carbon atom.

(V) 

iv) ammonolysis of alkyl esters of formula (V) with ammonia to provide (S)-(-)- α-ethyl- 2-oxo-l -pyrrolidine acetamide of formula (I).

(I)

Acording to another aspect the invention relates to a process for the preparation of (S)-(-)- α~ethyl-2-oxo-l-pyrrolidineacetamide of Formula (I), comprising the steps of : i) condensation of (S)-2-amino butanol of Formula (IΙ)and 4-halobutryl chloride, where halo group can be chloro, bromo or iodo in solvents to form α-ethyl-2-oxo pyrrolidine ethanol of Formula (III)

...........(II)............................................................. (III)

ii) oxidation of (S)-α-ethyl-2-oxo pyrrolidine ethanol to yield (S)-α-ethyl-2-oxo pyrrolidine acetic acid having the formula (IV)

(IV)

iii) reacting (S)-α-ethyl-2-oxo pyrrolidine acetic acid (IV) with alkyl haloformate of formula HaICOOZ in which Hal represents halogen atom and Z an alkyl radical having 1 to 4 Carbon atoms to provide alkyl ester of Formula (V) wherein, R is 1-4 Carbon atom.

(V) iv) ammonolysis of alkyl esters of formula (V) with ammonia to provide (S)-(-)- α-ethyl- 2-oxo-l -pyrrolidine acetamide of formula (I).

(I)

The new process of this invention comprises a sequential series of steps that involve:

Condensation of (S)-2-amino butanol and 4-halobutryl chloride, where halo group can be chloro, bromo or iodo is carried out in the presence of an inorganic as well as tertiary organic base, in solvents, such as, benzene, toluene, xylene, trimethyl benzene, chlorinated solvents, eg, methylene chloride, chloroform, carbon tetrachloride, dichloroethane etc, Dimethyl formamide (DMF), Methyl t-butyl ether and Tetrahydrofuran, to make α-ethyl-2-oxo pyrrolidine ethanol of Formula (III). The temperature of the condentation is in the range of 0 to 40⁰C and preferably 0 to 5°C.

(III)

The step of oxidation of (S)-α-ethyl-2-oxo pyrrolidine ethanol is carried out in the presence of an oxidising agent in acidic, basic and neutral medium, preferably a basic medium, to yield (S)-α-ethyl-2-oxo pyrrolidine acetic acid having the formula (IV) in good yields at -10 to 50⁰C.

(IV)

The oxidizing agent is selected from i) potassium permanganate in water (pH 7.0), in alkaline medium, pH (7-14) and even in acidic medium, pH (4-6), ii) Sodium or potassium dichromate in acidic medium.

The esterification of (S)-α-ethyl-2-oxo pyrrolidine acetic acid (IV) is effected with an alcohol in acidic medium or in presence of cationic ion exchange resin to make alkyl ester of Formula (V). Alternatively, the compound of Formula (V) can be formed by reacting the alkyl ester of Formula (IV) with alkyl haloformate of formula HaICOOZ in which Hal represents halogen atom and Z an alkyl radical having 1 to 4 Carbon atoms. The alkyl haloformate is preferably, commercially readily available, ethyl chloroformate, benzyl chloro formate and the like.

(V)

The ammonolysis of alkyl esters of formula (V) with ammonia in solvents is carried out in accordance with the method described by K. FOLKERS et al in J.Med. Chem, 14, 484- 487 (1971) or under 3.5 to 4 kg of Ammmonia pressure in autoclave , yield (S)-(-)- α- ethyl-2-oxo-l -pyrrolidine acetamide of formula (I).

(I)

Example- 1

4-chlorobutyryl chloride

(S)-2- amino butanol/D-(+)-2-amino butanol 

Preparation of (S)-α-ethyl-2-oxo pyrrolidine ethanol (III) 

184 g of anhydrous Na₂SO₄ is added to a suspension of 100 g (1.123 mole) of (S)-2- amino butanol in 800ml of Toluene at ambient temperature. The mixture is cooled to 0 to 5°C. Then, 188 g of powder potassium hydroxide is added to the mixture followed by the addition of 173.4 g of 4-chlorobutyryl chloride in 100 ml of Toluene drop wise at 0⁰C , with vigorous stirring . Ten hrs later, the reaction mixture is filtered over Hyflo-cel and the filtrate evaporated under reduced pressure . The crude product is purified by high vacuum distillation ( 137-14O⁰C at 2 mm pressure). Yield : 167.8 g ( 95%) [oc]²⁵= -27.46 (C=I, acetone)

Example-2 Preparation of (S)-α-ethyl-2-oxo pyrrolidine acetic acid (IV)

A mixture of 225 g of (S)-α- ethyl -2-oxo pyrrolidine ethanol and a solution of 44.8 g of sodium carbonate in 4500 ml of water placed in a 10 litre round bottomed flask. Then 340 g of potassium permanganate is added to the reaction mixture with vigorous stirring, during 3-4 hours, cooling the mixture to 0°-5°C by immersing in a bath of ice water. Allow the reaction mixture to attain room temperature gradually. 15 hours later, filter off the precipitated manganese dioxide, concentrated the filtrate to about 1000 ml under reduced pressure and acidified with dilute sulphuric acid up to pH 2 followed by the saturation with NaCl. Cover the solution with a layer of dichloromethane. Separate the dichloromethane layer and extract the aqueous layer two to three times with 100 ml portions of dichloromethane and distilled off on rotavapor. Recrystallised the crude acid (209 g) from 210 ml of toluene; filter and wash with toluene . Yield : 130 gm (54 %) ; MP 124⁰C ; [oc]²⁵= -24.32 (c=l, acetone)

Example-3

Preparation of (S)-α-ethyl-2-oxo pyrrolidine acetic acid methyl ester (V) 

 R- METHYL

A mixture of 34 g (S)-α-ethyl-2-oxo pyrrolidine acetic acid and 100 ml of methanol was taken in a 250 ml of round bottom flask fitted with reflux condenser and added 3.4 g ion exchange resin 225H^tO the reaction. Allowed to reflux for 12 hours. Filter the resin. The crude product in methanol was taken as such for ammonolysis.

Example-4 Preparation of (S)-(-)-α-ethyl-2-oxo-l-pyrrolidineacetamide (I)  LEVETIRACETAM

(S)-α-ethyl-2-oxo pyrrolidine acetic acid methyl ester in MeOH from Example 3 is placed in autoclave under 4 kg of ammonia pressure at 25°C. The reaction mixture was allowed to stir for about 16 hours. The solvent was distilled off under reduced pressure. The crude (S)-(-)-α-ethyl-2-oxo-l-pyrrolidineacetamide 30 g was recrystallised from 240 ml Acetone to get 20.4 g pure product.

Yield : 20.4 (60%); MP : 117°C ; [oc]²⁵= -91.75 (C=I, acetone)

......................

PATENT

ROUTE FROM  D-(+)-2-amino butanol and with the dihydro-furan-2-one/γ-butyrolactone

http://www.google.com/patents/WO2008077035A2?cl=en

Levetiracetam obtained by the process described herein is believed to have less than 0.1% of one or more of the following structural related impurities: 2- Amino butric acid, S-aminobutyramide hydrochloride, chloramide of Formula A and (-)-(S)-alpha-ethyl-2-oxo-1 -pyrrolidine acetic acid of Formula II.

Formula A

Also provided is a process for making levetiracetam by a) reacting the compound of the Formula III:

(III) with an oxidizing agent in the presence of a base and a phase transfer catalyst to provide the compound of the Formula II:

(II) b) reacting the compound of the Formula Il with a chlorinating agent to obtain an intermediate acid chloride of the formula (H-A):

(H-A)

c) reacting the compound of the formula (M-A) with a source of ammonia. The process for the preparation of levetiracetam of Formula I is summarized in the scheme 4.

Scheme-4: Process for preparing levetiracetam.

Also provided is a process for preparing the compound of Formula III by reacting D-(+)-2-amino butanol of the Formula Vl:

Formula Vl with the dihydro-furan-2-one of the Formula IV:

Formula IV to provide (S)-α-ethyl-2-oxopyrrolidine ethanol of the Formula III, which may be then converted to levetiracetam. The process for the preparation of the intermediate III is summarized in the scheme 5:

.....................................................(Vl) .....................(IV)............................................... (III)

Scheme-5: Process for preparing Formula III

EXAMPLE1 : PREPARATION OF (-)-(S)-α-ETHYL-2-OXO-1-PYRROLIDINE ACETAMIDE (FORMULA I) levetiracetam

S-aminobutyramide hydrochloride (25 g) and dichloromethane (300 ml) were^harged into a clean dry4 neck round bottom flask and stirred at about

10⁰C for about 10 minutes. Tetra-n-butyl ammonium bromide (1 1.6 g) was added and stirred at a temperature of about -1O⁰C for about 10 minutes. Potassium hydroxide (20.2 g) was added at a temperature of about -10⁰C and stirred for 15 minutes followed by addition of mixture of 4-chloro butyrlchloride (12.7 g) and dichloromethane (25 ml) was added slowly at a temperature of about -6°C over a period of about 45 minutes. The resultant reaction mixture was stirred for about 45 minutes. Potassium hydroxide (20.2 g) was added at a temperature of about - 1O⁰C and stirred for about 15 minutes followed by addition of 4-chlorobutyrl chloride (7.6 g) and dichloromethane (25 ml) slowly over a period of about 30 minutes and stirred for about 45 minutes. A lot of potassium hydroxide (10.1 g) was added at a temperature of about -10⁰C and stirred for about 15 minutes followed by addition of 4-chlorobutyrl chloride (7.6 g of) dissolved in dichloromethane (25 ml) slowly over about 30 minutes. The resultant reaction mixture was stirred at a temperature of about -2°C for about 5 hours. Potassium hydroxide (5.05 g) was added followed by stirring for about 2 hours. The separated unwanted solid was filtered and the solid was washed with dichloromethane (50 ml). pH of the filtrate was adjusted to about 7 by addition of acetic acid (0.8 ml). The organic layer was dried over anhydrous sodium sulphate. The obtained clear organic layer was distilled off completely at about 35°C under vacuum. Ethyl acetate (25 X 2 ml) was added to the residue and distilled completely under vacuum to remove the traces dichloromethane, yielding the title compound as a solid residue.

To the obtained residue ethyl acetate (10 ml) was added at a temperature of about 25°C to about 30⁰C and cooled to about 0°C followed by stirring for about 30 minutes. The separated solid was filtered and the solid was washed with precooled ethyl acetate (10 ml). The obtained solid was dried at about 40⁰C under vacuum for about 3 hours to afford 27 g of pure title compound. Purity by HPLC: 99.94%. Purity by chiral HPLC: 99.7%.

EXAMPLE 2: PREPARATION OF (S)-α-ETHYL-2-OXO-1-PYRROLIDINE

ETHANOL (FORMULA III)

D-2-amino butanol (50 g) and γ-butyrolactone (62 g) were charged into a clean and dry autoclave containing acetic acid (3.6 g). The reaction mixture was maintained under about 20 kg/cm² to about 25 kg/cm² nitrogen pressure at a temperature of about 220⁰C to about 23O⁰C for about 15 to about 20 hours. The resultant reaction mixture was cooled to a temperature of about 25⁰C to about 35°C to afford the 109.2 g of title compound as a residue. Purity by HPLC: 91.79%

EXAMPLE 3: PREPARATION OF (S)-α-ETHYL-2-OXO PYRROLIDINE ACETIC ACID (FORMULA II)

Potassium hydroxide (10 g) was dissolved into water (180 ml) and cooled to a temperature of about 1 O⁰C. Tetra-n-butyl ammonium bromide (2 g) and (S)- α-ethyl-2-oxo pyrrolidine ethanol (10 g) in methylene chloride (18 ml) were charged followed by stirring for about 10 minutes. Potassium permanganate (15 g) was charged followed by stirring at a temperature of about 30⁰C for about 8 hours. The resultant reaction mixture was filtered through a celite bed and the celite was washed with water (100 ml) followed by separation of organic and aqueous layers. The separated aqueous layer was charged into a clean and dry round bottom flask followed by cooling to about 0°C. pH of the reaction solution was adjusted to about 3 by the addition of hydrochloric acid (2 ml) followed by stirring for about 5 minutes. To the resultant reaction mixture sodium phosphate (25 g) was added followed by stirring for about 10 minutes. Toluene (150 ml) was added into the reaction solution and about 50% of the solvent was distilled off. The resultant reaction solution was extracted with dichloromethane (5*50 ml) followed by separation of organic and aqueous layers. The organic layer was dried over anhydrous sodium sulphate (10 g). Organic layer was distilled completely at a temperature of about 30⁰C under vacuum to obtain the title compound as a residue.

To the residue toluene (10 ml) was added and stirred at 0°C for about 30 minutes. The separated solid was filtered and the solid was washed with toluene (5 ml). The obtained solid was dried at a temperature of about 60⁰C under vacuum for about 1 hour to afford the pure 5 3 fj πf title compound.

Purity by HPLC: 97%.

EXAMPLE 4: PREPARATION OF (-)-(S)-α-ETHYL-2-OXO-1 -PYRROLIDINE ACETAMIDE (FORMULA I)LEVETIRACETAM

(-)-(S)-α-ethyl-2-oxo-1 -pyrrolidine acetic acid (5 g) of Formula Il and dichloromethane (50 ml) were charged into a clean and dry round bottom flask and stirred for about 20 minutes. The resultant reaction solution was cooled to about -25°C followed by dropwise addition of a mixture of thionyl chloride (4.5 ml) and dichloromethane (10 ml) slowly over a period of about 10 minutes. The resultant reaction mixture was stirred at a temperature of about -15°C for about 90 minutes. After completion of the reaction thionyl chloride was expelled by purging with nitrogen gas at about -10⁰C for about 90 minutes. Dry ammonia gas was passed slowly into the mixture at about -10⁰C for about 3 hours. The separated solid was filtered and the solid was washed with dichloromethane (50 ml). The resultant filtrate was distilled completely under vacuum to afford the title compound as a residue.

To the crude obtained, ethyl acetate (10 ml) was charged followed by stirring at a temperature of about 30⁰C for about 15 minutes. The separated solid was filtered and the solid was dried at about 6O⁰C under vacuum for about 3 hours to afford 4 g of the title compound. Yield: 80.46% Purity by HPLC: 98.09%. Purity by chiral HPLC: 99.73%. 

EXAMPLE-5: PREPARATION OF(S)-α-ETHYL-2-OXO-1 -PYRROLIDINE ETHANOL (FORMULA III)

D-2-amino butanol (0.515 g) and γ-butyrolactone (0.5 g) were charged into a clean and dry TFM liner vessel. The vessel was placed in microwave oven and irradiated radiation for 1 hour at a temperature of about 200⁰C to give -1-g-of title compound.

Purity: 81.69% by HPLC at 16.56 retention time (RT)

4-hydroxy-N-1-hydroxymethyl-propyl)butyramide intermediate: 8.81% at 6.122 Impurity: 5.71% at 14.32 RT

..............................................

PATENT

http://www.google.im/patents/WO2003014080A2?cl=en

Step 1 - Synthesis of methyl (S)-aminobutyrate hydrochloride

.................................(23) .............................................................(24)

5.0g of (S)-amino butyric acid (23) was suspended in 50 ml of methanol and stirred at 0-5°C. 6.35g of thionyl chloride was added dropwise over 45 min to form a clear solution. After stirring for 20 hours at room temperature, the reaction was concentrated under reduced pressure to dryness and the almost colourless residue solidified to give the required product which was dried in an oven at 50°C under vacuum (7.6g; 102% crude yield). The same reaction was scaled-up from 200g of the amino acid and provided 296g (99.5% yield) of product (24). Analysis gave the following results: 1H NMR (DMSO-de) : d 0.94 (3H, t) 1.88 (2H, q) 3.75 (3H, s) 3,9 (1H, m) 8,8

(3H, m). m.p. : 107°C-110°C IR : 2876 cm ¹, 1742 cm ¹.

TLC : Si0₂, 20%MeOH/80%EtOAc/ l%NH OH, UV & IR. (TLC is an abbreviation for thin layer chromatography).

Step 4 - Ammonolysis of (S)-PBM to give Levetiracetam.

11.3g of ammonia gas was condensed in 13.2 ml of water at approximately 0°C and the temperature was maintained at 0-5°C. Then 20g of (S)-PBM (26) was added dropwise over a period of 10 min and reaction mixture was maintained at 5°C and stirred for minimum 8 hrs (reaction was complete as indicated by TLC). The reaction mixture was then evaporated to dryness under vacuum and dried by means of toluene (2x50 ml) to give minimum 17g (92%) of crude (S)-pyrrolidinobutyramide (crude Levetiracetam) as an off-white to beige solid. Analysis gave the following results (chiral and achiral HPLC): The extent of racemisation was 0.0%. The extent of hydrolysis was measured to 2.5%. Example 2

17.3g of ammonia gas were condensed in 22 ml of water at 0°C and temperature maintained at 0-5°C. Then 20g of (S)-PBE obtained via SMB separation of the corresponding racemic mixture were added dropwise over a period of 2 min and the reaction mixture was maintained at 5°C and stirred for 96 hrs (reaction was complete as judged by TLC). The reaction mixture was then evaporated to dryness under vacuum and dried by means of toluene (2x100 ml) to give minimum 14.8g (87%) of crude (S)-pyrrolidinobutyramide as a brown orange solid. Analysis gave the following results (chiral and achiral HPLC): The extent of racemisation was 1.6% with 6.6% hydrolysis.

REFERENCES

WO2001064637A1 *	21 Feb 2001	7 Sep 2001	Edmond Differding	2-oxo-1-pyrrolidine derivatives, process for preparing them and their uses
EP0162036A1 *	14 May 1985	21 Nov 1985	U C B, S.A.	(S)-alpha-ethyl-2-oxo-1-pyrrolidinacetamide
EP0165919A1 *	14 May 1985	27 Dec 1985	U C B, S.A.	(R)-alpha-ethyl-2-oxo-1-pyrrolidinacetamide
GB1309692A *				Title not available

WO2006090265A2 *	Feb 28, 2006	Aug 31, 2006	Ranbaxy Lab Ltd	Processes for the preparation of levetiracetam, its intermediate and the use of levetiracetam in pharmaceutical compositions
WO2006095362A1 *	Jan 20, 2006	Sep 14, 2006	Rubamin Ltd	Process for preparing levetiracetam
WO2006103696A2 *	Jan 20, 2006	Oct 5, 2006	Rubamin Ltd	Process for preparing levetiracetam and racemization of (r)- and (s)-2-amino butynamide and the corresponding acid derivatives
US4943639 *	Feb 16, 1989	Jul 24, 1990	U C B Societe Anonyme	Treatment of hypoxic and ischemic aggressions of the central nervous system, head injuries
US6107492 *	May 7, 1999	Aug 22, 2000	Ucb, S.A.	By optical resolution of a racemic mixture of alpha-ethyl-2-oxo-1-pyrrolidine acetamide by chromatography using silica gel supporting amylose tris(3,5-dimethylphenylcarbamate) as a packing material
US20050182262 *	Feb 16, 2005	Aug 18, 2005	Acharyulu Palle V.R.	Reacting an amino acid or acid salt with a halogenating agent (thionyl chloride, phosphorous pentachloride or oxalyl chloride) , to form an intermediate, reacting the intermediate with ammonia; amidation; chemical intermediate to form Levetiracetam

WO2006090265A2 *	Feb 28, 2006	Aug 31, 2006	Ranbaxy Lab Ltd	Processes for the preparation of levetiracetam, its intermediate and the use of levetiracetam in pharmaceutical compositions
WO2006095362A1 *	Jan 20, 2006	Sep 14, 2006	Rubamin Ltd	Process for preparing levetiracetam
WO2006103696A2 *	Jan 20, 2006	Oct 5, 2006	Rubamin Ltd	Process for preparing levetiracetam and racemization of (r)- and (s)-2-amino butynamide and the corresponding acid derivatives
US4943639 *	Feb 16, 1989	Jul 24, 1990	U C B Societe Anonyme	Treatment of hypoxic and ischemic aggressions of the central nervous system, head injuries
US6107492 *	May 7, 1999	Aug 22, 2000	Ucb, S.A.	By optical resolution of a racemic mixture of alpha-ethyl-2-oxo-1-pyrrolidine acetamide by chromatography using silica gel supporting amylose tris(3,5-dimethylphenylcarbamate) as a packing material
US20050182262 *	Feb 16, 2005	Aug 18, 2005	Acharyulu Palle V.R.	Reacting an amino acid or acid salt with a halogenating agent (thionyl chloride, phosphorous pentachloride or oxalyl chloride) , to form an intermediate, reacting the intermediate with ammonia; amidation; chemical intermediate to form Levetiracetam

O2005023763A1 *	2 Sep 2004	17 Mar 2005	Surender Kumar Dhingra	Process for the preparation of pure levetiracetam
WO2005028435A1 *	13 Sep 2004	31 Mar 2005	Ucb Sa	Process for preparing 2-oxo-1-pyrrolidine derivatives
WO2006095362A1 *	20 Jan 2006	14 Sep 2006	Rubamin Ltd	Process for preparing levetiracetam
WO2007031263A1 *	12 Sep 2006	22 Mar 2007	Ucb Sa	4-substituted pyrr0lidin-2-0nes and their use
WO2008012268A1 *	20 Jul 2007	31 Jan 2008	Zach System Spa	Process for the preparation of levetiracetam
EP1806339A1	20 Dec 2006	11 Jul 2007	U C B, S.A.	Process for the preparation of 2-oxo-1-pyrrolidine derivatives
EP2147911A1	24 Jul 2008	27 Jan 2010	ZaCh System S.p.A.	Process for the preparation of levetiracetam
US7132552 *	3 Feb 2004	7 Nov 2006	Teva Pharmaceutical Industries, Ltd.	Reacting aminobutanamide hydrochloride with chlorobutyl chloride in solvent such as acetonitrile and methyl tert-butyl ether in base
US7629474	13 Sep 2004	8 Dec 2009	Ucb Pharma S.A.	cost effective way producing Levetiracetam; catalysis the amidation reaction from 5-hydroxy-4-n-propyl-furan-2-one intermediate
US7902380	21 Nov 2005	8 Mar 2011	Apotex Pharmachem Inc.	Process for the preparation of (S)-alpha-ethyl-2-oxo-1-pyrrolidineacetamide and (R)-alpha-ethyl-2-oxo-pyrrolidineacetamide
US7939676	17 Sep 2009	10 May 2011	Zach System S.P.A.	Process for the preparation of levetiracetam
US8338621	19 Dec 2006	25 Dec 2012	Ucb S.A.	Process for the preparation of 2-oxo-1-pyrrolidine derivatives

WO2003014080A2 *	5 Aug 2002	20 Feb 2003	Celal Ates	Oxopyrrolidine compounds, preparation of said compounds and their use in the manufacturing of levetiracetam and analogues
GB1309692A *				Title not available
US4696943 *	14 May 1985	29 Sep 1987	U C B Societe Anonyme	Antihypoxia and antiischemic agents

US7939676 *	Sep 17, 2009	May 10, 2011	Zach System S.P.A.	Process for the preparation of levetiracetam
WO2008077035A2 *	Dec 18, 2007	Jun 26, 2008	Reddys Lab Ltd Dr	Processes for the preparation of levetiracetam
WO2009050735A1 *	Oct 15, 2008	Apr 23, 2009	Lupin Ltd	A novel polymorph of levetiracetam and a process for its preparation

..............

P.S. : The views expressed are my personal and in no-way suggest the views of the professional body or the company that I represent.

P.S. : The views expressed are my personal and in no-way suggest the views of the professional body or the company that I represent.

P.S. : The views expressed are my personal and in no-way suggest the views of the professional body or the company that I represent.

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