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|Title:||An asymmetric synthesis of Levetiracetam|
|Keywords:||Asymmetric synthesis;Heterocycles;Strecker reaction;Chiral auxiliaries;Stereoselective synthesis|
|Abstract:||An asymmetric synthesis of (S)-levetiracetam has been developed through application of a Strecker reaction using [(1S)-1-(4-methoxyphenyl)ethyl]amine hydrochloride as a chiral auxiliary. Addition of propanaldehyde to a solution of sodium cyanide and [(1S)-1-(4-methoxyphenyl)ethyl]amine hydrochloride in the mixture of methanol and water at 25-30°C afforded diastereomerically pure 2-[2-(4-methoxyphenyl)-(S)-methylethyl-amino]-(S)-butyronitrile hydrochloride compound 4. In this reaction cyanide group attack at less hindered side that is re-face of the imine intermediate gave the diastereomerically pure nitrile 4. Which upon hydrolysis in the presence of 6 M aqueous hydrochloride solution obtained enantiomerically pure (S)-2-aminobutyric acid hydrochloride 5, is a key intermediate for the (S)-levetiracetam. This intermediate further react with SOCl2 in presence of methanol formed S-2-amino methyl butyrate as in situ intermediate which on further ammonalysis in the presence of methnaolic ammonia as a solvent under ammonia pressure provided S-2-amino butyramide hydrochloride 6 which further condensed with 4-chlorobutyryl chloride 7 and followed by cyclization in the presence of potassium hydroxide, dichloromethane solvent used catalytic amount of tetra butyl ammonium bromide afforded crude (S)-levetiracetam 1, further recrystalization in the presence of ethyl acetate obtained pure (S)-levetiracetam 1|
|Appears in Collections:||IJC-B Vol.53B(09) [September 2014]|
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