Chemo- and stereoselective reduction of an alpha-cyanoketone by bakers' yeast at low temperature.

[formula: see text] The bakers' yeast mediated reduction of 3-oxo-3-phenylpropanenitrile (1) proceeds at 4 degrees C to give exclusively (S)-3-hydroxy-3-phenylpropanenitrile (3) in 59% yield. This is in contrast to the corresponding reaction at room temperature which yields a mixture of reduction and alkylation products. This work demonstrates the use of low temperature to improve yeast selectivity.