Asymmetric Reduction of β-Ketonitriles with a Recombinant Carbonyl Reductase and Enzymatic Transformation to Optically Pure β-Hydroxy Carboxylic Acids

α-Ethylation is concomitant with the reduction of aromatic β-ketonitriles catalyzed by whole-cell biocatalysts. Use of isolated carbonyl reductase has completely eliminated this competing reaction. (R)-β-Hydroxy nitriles were obtained via a reduction catalyzed by a recombinant carbonyl reductase with excellent optical purity and were further converted to (R)-β-hydroxy carboxylic acids via a nitrilase-catalyzed hydrolysis. The present study allows ready access to both chiral β-hydroxy nitriles and β-hydroxy carboxylic acids of pharmaceutical importance.