Abstract: A process is disclosed for the preparation of D-lactic acid from lactate racemic mixture. It comprises the steps of: (i) hydrolysis of an alkyl lactate racemic mixture in the presence of an esterase as a catalyst to hydrolyze L-alkyl lactate; (ii) separation of unhydrolyzed D-alkyl lactate with an organic solvent, such as n-hexane or a high alcohol; and (iii) chemical hydrolysis of the separated portion obtained from step (ii) with a base to obtain D-lactic acid. The esterase can be selected from the group consisting of pig pancreas lipase of the trade name Sigma L-3126, wheat germ lipase of the trade name Sigma L-3001, Candida cyclindracea lipase of the trade name Sigma L-1754, Rhizopus lipase of the trade name Serva 27930, Mucor javanicus lipase of the trade name Fluca 62304, Aspergillus niger lipase of the trade name Fluca 62301, Rhizopus arrhizus lipase of the trade name Boehringer Mannherin 414590, and Candida cylindracea cholesterol esterase of the trade name Boehringer Mannherin 396800.

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%.