Candida tenuis xylose reductase catalysed reduction of acetophenones: the effect of ring-substituents on catalytic efficiency.

The catalytic efficiencies of Candida tenuis xylose reductase catalysed reductions of mono-substituted acetophenones are in reasonable correlation with the σ-Hammett coefficients of the substituted phenyl groups. Variations of the substrate transformation rates are hence mainly caused by mesomeric and inductive effects of the substituents, while differences in substrate binding have a secondary relevance. Some substrate (1)H NMR chemical shifts and carbonyl IR absorption bands are in reasonable accordance with the catalytic activities and allow the estimation of the transformation rates with good accuracy. The resulting substituted (S)-1-phenyl ethanols are generated in very high enantiomeric excess.