Synthesis of (R)-(-)-Mandelic Acid Ethyl Ester by Asymmetric Reduction of Ethyl Benzoylformate with Yeast Cells

An efficient yeast cell biotransformation process was set up for asymmetric synthesis of (R)-(-)-mandelic acid ethyl ester, a key drug intermediate. Saccharomyces cerevisiae 21 was selected as optimum strain for biotransformation. The optimum reduction conditions are as follows: substrate concentration 20 g/L, cell concentration 140 g/L, reaction time 36 h, temperature 30 0C. Conversion and enantiometric excess of (R)-(-)-mandelic acid ethyl ester reached 99.8 % and 100%.