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

An efficient yeast cell biotransformation process was set up for asymmetric synthesis of (R)-(-)-mandelic acid methyl ester, a key drug intermediate. Saccharomyces cerevisiae 21 was selected as optimum strain for biotransformation. The optimum reduction conditions are as follows: substrate concentration 22 g/L, cell concentration 150 g/L, reaction time 36 h, 30°C, pH5.0. Conversion and enantiometric excess of (R)-(-)-mandelic acid methyl ester reached 99.4% and 99.9%.