Enzymatic Syntheses of Chiral Building Blocks from Racemates: Preparation of (1 R ,3 R )‐Chrysanthemic, ‐Permethrinic and ‐Caronic Acids from Racemic, Diastereomeric Mixtures

The use of enantioselectivley reactive enzymes on the laboratory scale offers great advantages. With procine liver esterase, for example, chrysanthemic acid (1 R ,3 R )‐ 1 can be prepared from a mixture of the four esters with (1 S ,3 R )‐, (1 R ,3 S )‐ (1 S ,3 S )‐, and (1 R ,3 R )‐configuration. Diastereoselective hydrolysis of the mixture affords the trans ‐acids (1 S ,3 S )‐1 and (1 R ,3 R )‐1. Enantioselective hydrolysis of the trans ‐ester leads to (1 R ,3 R )‐1, which is of interest in connection with the pyrethroid insecticides.