Abstract: A process for the preparation of optically active D-amino acid and its esters, comprising the steps of: (a) preparing a reaction mixture containing an DL-amino acid ester and a lipase or an acylase in an aqueous solution; (b) reacting the reaction mixture at temperatures between 4.degree. and 60.degree. C.; and (c) using an organic extractant to separate the reaction mixture into an upper layer, which contains an optically active D-amino acid ester, and a lower layer, which contains L-homophenylalanine. The optically active D-amino acid ester can be chemically hydrolyzed to obtain an optically active D-amino acid The lipase can be selected from the group consisting of Aspergillus niger lipase, Pseudomonas sp. lipase, Rhizopus sp. lipase, porvine pancreas lipase, wheat germ lipase, and hog pancreas lipase, and the acylase can be porcine kidney acylase.

Abstract: A process for the preparation of optically active D-homophenylalanine and its esters, comprising the steps of: (a) preparing a reaction mixture containing an DL-homophenylalanine ester and a lipase or an acylase in an aqueous solution; (b) reacting the reaction mixture at temperatures between 4.degree. and 60.degree. C.; and (c) using an organic extractant to separate the reaction mixture into an upper layer, which contains an optically active D-homophenylalanine ester, and a lower layer, which contains L-homophenylalanine. The optically active D-homophenylalanine ester can be chemically hydrolyzed to obtain an optically active D-homophenylalanine. The lipase can be selected from the group consisting of Aspergillus niger lipase, Pseudomonas sp. lipase, Rhizopus sp. lipase, porvine pancreas lipase, wheat germ lipase, and hog pancreas lipase, and the acylase can be porcine kidney acylase. Many of these lipases or acylase provide an enantiometric excess of more than 95%.