Asymmetric Reduction of Aromatic Ketones with Yeast Cells

Asymmetric reduction of aromatic ketones with baker’s yeast was studied. The effects of some factors, such as reaction temperature, reaction time, substrate concentration and yeast concentration, on the acetophenone conversion and (S)- 1-phenylethanol enantioselectivity were investigated by orthogonal experiments. The results indicate that the acetophenone conversion is affected orderly by substrate concentration, reaction time, reaction temperature and yeast concentration. The enantiomeric excess of (S)- 1-phenylethanol is affected orderly by reaction temperature, substrate concentration, yeast concentration and reaction time. Suitable biotransformation conditions for acetophenone are 33 ℃, 30 h, 70 mmol/L acetophenone and 170 g/L baker’s yeast. The effect of the aromatic ketone structure on the enantioselectivity was also studied. The enantiomeric excess value is enhanced when the volume of the R_2 group in aromatic ketones increases. The change in enantioselectivity accords with the Prelog’s rule. The highest enantiomeric excess value reaches 96.4%.