Enzymatic Preparation of Enantiomerically Enriched Tertiary a-Benzyloxy Acid Esters. Application to the Synthesis of (S)-(-)-Frontalin

Enzymatic preparation of enantiomerically enriched tertiary a-benzyloxy acid esters is described. Enantioselective hydrolysis of the racemic esters of the formula [R-C(CH₃)(OCH₂Ph)CO₂CH₃] by lipase OF (from Candida cylindracea, Meito Sangyo Co.) was successfully carried out on a preparative scale. With the asymmetric carbon atom possessing a tertiary benzyloxy group, (S)-(-)-frontalin, a component of the aggregation pheromone of the southern pine beetle, was efficiently synthesized.