Resolution of (R,S)-2-phenylpropanoic acid by enantioselective esterification with dry microbial cells in organic solvent

The microbial direct esterification of racemic 2-phenyl-1-propanoic acid with ethanol by lyophilized mycelium of Aspergillus oryzae MIM and Rhizopus oryzae CBS 112.07 in organic solvents has been investigated. Dry cells of Rhizopus oryzae CBS 112.07 gave the (R)-ethyl ester with high enantiomeric excess (>97%) when the biotransformation was carried out in heptane or pentadecane. Dry mycelium of Aspergillus oryzae MIM furnished the ethyl ester of (S)-(+)-2-phenylpropanoic acid with 90% enantiomeric excess when used in toluene in a temperature range of 20-40°C.