Facile preparation of methyl 5-aryl-4-hydroxyhex-2(E)-enoate,chiral synthon of bisabolane-type sesquiterpenes,based on lipase-catalyzed kinetic resolution and rearrangement of an aryl group

The lipase-catalyzed enantioselective acetylation of racemic methyl (4S¹,5S¹)-4-aryl-5-hydroxyhex-2(E)-enoates 1a–h was performed and efficient resolutions were achieved (E >400) by using CAL-B. After brosylation of the obtained optically active 1a–h, solvolysis of brosylates 13a–h afforded the corresponding methyl (4S¹,5S¹)-5-aryl-4-hydroxyhex-2(E)-enoates 3a–h (26–94% yield). The yields of 3a and 3c on the solvolysis of the corresponding 13 were 92% and 40%, respectively, while solvolysis of the corresponding tosylate was reported at 70% and 17%, respectively. This procedure is a facile and practical route to the synthesis of bioactive and optically active bisabolane-type sesquiterpenes.