Drum & Roth
Processes for preparing optically active (S)-.alpha.-aryl propionic acid or ester therof
 A process for preparing an optically active (S)-.alpha.-aryl propionic acid, by hydrolyzing a racemic thioester of .alpha.-aryl propionic acid at various temperature in different aqueous organic solvents in the presence of an (S)-stereoselective lipase to form an (S)-.alpha.-aryl propionic acid product, while the unreacted (R)-thioester of .alpha.-aryl propionic acid can be converted to the corresponding (S)-thioester of .alpha.-aryl propionic acid via a racemization reaction by adding a base as the catalyst in the solution and then hydrolyzing by the lipase described as above so that the (S)-.alpha.-aryl propionic acid can be obtained theoretically at a conversion of 100% and with high optical purity. The invention also relates to a process for preparing an optically active (S)-.alpha.-aryl propionic acid ester, by adding separately additional alcohol in said various organic solvents and carrying out the transesterification of a racemic thioester of .alpha.-aryl propionic acid to form an (S)-.alpha.-aryl propionic acid ester product, while the unreacted (R)-thioester of .alpha.-aryl propionic acid can be converted to the corresponding (S)-thioester of .alpha.-aryl propionic acid via a racemization reaction by means of the base added in the solution as the catalyst and then transesterifying again by the lipase as described above so that an (S)-.alpha.-aryl propionic acid ester product can be obtained at, theoretically, a conversion of 100% and with high optical purity. 
National Science Council of Republic of China
C
C07C
inventional
Chun-Sheng Shau-Wei
Chang Tsai