Chiral alcohol synthesis with yeast carbonyl reductases

Abstract

Synthesis of chiral alcohols, ( R)- and ( S)-4-chloro-3-hydroxybutanoate ethyl esters (CHBE), was performed through the enzymatic asymmetric reduction of 4-chloroacetoacetate ethyl ester (CAAE). The enzymes reducing CAAE to ( R)- and ( S)-CHBE were found to be produced by Sporobolomyces salmonicolor and Candida magnoliae, respectively. The enzyme of S. salmonicolor is a novel NADPH-dependent aldehyde reductase (AR) belonging to the aldo-keto reductase superfamily. The C. magnoliae enzyme also seems to be a novel NADPH-dependent carbonyl reductase. When AR-overproducing Escherichia coli transformant cells or C. magnoliae cells were incubated in an organic solvent–water two-phase system, 300 or 90 mg/ml of CAAE was almost stoichiometrically converted to ( R)- or ( S)-CHBE (>92% e.e.), respectively.