One-pot chemo-enzymatic enantiomerization of racemates

A new one-pot chemo-enzymatic procedure was developed for enantiomerization of racemates based on enzymatic enantiospecific oxidation of a substrate and chemical non-enantiospecific reduction of the product. The principle is shown as follows for the l-proline production.l-Proline and l-pipecolate were produced from racemic proline and pipecolate by means of d-amino acid oxidase and sodium borohydride in high yield in this reaction system [J.W. Huh, K. Yokoigawa, N. Esaki, K. Soda, Biosci., Biotechnol., Biochem. 56 (1992) 2081]. dl- and l-Lactate were dl-enantiomerized in a one-pot reaction system containing l-lactate oxidase and sodium borohydride in the similar manner [S. Mukoyama, K. Yamanaka, T. Oikawa, K. Soda, Nippon Nogei Kagaku Kaishi 73 (1999) 62]. Pyruvate was also converted to an equimolar amount of d-lactate in the same system. d-α-Hydroxybutyrate can be produced from the dl- and l-isomers, and α-ketobutyrate in the same manner though slowly. This method is applicable to production of other chiral compounds from the corresponding racemates.