Stereoselective Reactions. XVI. : Total Synthesis of (-)-β-Bourbonene by Employing Asymmetric (2+2) Photocycloaddition Reaction of Chiral Butenolide

Abstract

Total synthesis of (-)-β-bourbonene (3) was achieved by employing the (2+2) photocycloaddition reaction of (S)-γ-pivaloyloxymethyl-β-methyl-γ-butenolide (5e) with cyclopentenone ethyleneacetal (15). The major photoadduct (16) was readily converted to the cis, anti, cis-tricyclo[5.3.0.0^{2, 6}]decane system (22) in 70% yield. Further transformation provided the optically pure title compound (3).