BACKGROUND: The enantioselectivity of reduction of ethyl 2-oxo-4-phenylbutyrate (EOPB) to synthesize ethyl (R)-2-hydroxy-4-phenylbutyrate ((R)-EHPB) catalyzed with baker's yeast in diethyl ether can be improved by the introduction of alpha-phenacyl chloride (PC). However, the toxicity of PC to the yeast results in a decrease in the catalytic activity of yeast. In order to overcome this limitation, four strategies for PC addition were designed. The effect of PC on the catalytic behavior of baker's yeast was studied using spectrum analysis of alcohol dehydrogenase from yeast (YADH). RESULTS: After being pretreated with PC according to Strategy 4, the pretreated baker's yeast possessed good catalytic activity and enantioselectivity for the reduction of EOPB to produce (R)-EHPB. Under the optimum pretreatment conditions, the conversion of EOPB, the yield of EHPB and the enantiomeric excess of (R)-EHPB reached 96%, 90% and 92%, respectively. Significant changes were observed in the UV absorption and fluorescence spectra of the YADH from the yeast pretreated by PC. CONCLUSION: The change of catalytic behavior of yeast after the pretreatment was probably caused by an interaction between yeast and PC. The reactive halomethyl group in PC molecule plays a key role for the interaction. (C) 2008 Society of Chemical Industry