Total synthesis of α- and β-himachalene by an intermolecular Diels–Alder approach

Abstract

A total synthesis of α-himachalene (2) and β-himachalene (3) has been achieved in eleven steps and in an effective overall yield of 21% from 4,4-dimethyl-2-cyclohexenone (4). The synthesis involves keto ester 7 as a key intermediate which is conveniently prepared by the Diels–Alder addition of dienone ester 6 to isoprene.