Structure and synthesis of a new ketone from Cedrus species; some new constituents of C. atlantica Manet

Abstract

Details are given of the structure and two syntheses of a new C₁₂ ketone [4-(4-methylcyclohex-3-enyl)pent-3-en-2-one] isolated from the essential oils of Cedrus atlantica Manet and C. deodara Loud. The absolute configuration of the C₁₂ ketone follows from the synthesis of the natural enantiomorph by acetylation of (+)-p-mentha-1,8-diene at C-9. The presence of deodarone [2,2,6-trimethyl-6-(4-methylcyclohex-3-enyl)tetrahydro-4-pyrone] in Cedrus atlantica is reported for the first time and clear proof of its structure is presented by dehydration to α-atlantone [2-methyl-6-(4-methylcyclohex-3-enyl)hepta-2,5-dien-4-one]. Other new constituents of Cedrus atlantica include α-caryophyllene alcohol, obtained for the first time as a natural product, epi-β-cubenol, α-ionone, and two new epoxides, epoxy-β-himachalene and epi-epoxy-β-himachalene (2,4a,5,6,7,8,9,9a-octahydro-3,5,5,9-tetramethyl-9,9a-epoxy-1H-benzocycloheptene).