Patent ID: 7153675

Claim:
A process for the preparation of 2(S)-alkyl-5-halogenpent-4-ene carboxylic esters by enzymatic hydrolysis, comprising the steps a) enzymatic hydrolysis of racemic 2-alkyl-5-halogenpent-4-ene carboxylic esters in aqueous and alkaline medium in the presence of an esterase; b) isolation of 2(S)-alkyl-5-halogenpent-4-ene carboxylic esters by extraction with an organic solvent; c) isolation of 2(R)-alkyl-5-halogenpent-4-ene carboxylic acids from the aqueous-alkaline medium; d) esterification of 2(R)-alkyl-5-halogenpent-4-ene carboxylic acids to 2(R)-alkyl-5-halogenpent-4-ene carboxylic esters, e) subsequent racemization to form 2-alkyl-5-halogenpent-4-ene carboxylic esters; and f) return of the racemate obtained in step e) to step a), if necessary together with fresh racemic 2-alkyl-5-halogenpent-4-ene carboxylic esters.