2-Acetyl-3,5,5,9-tetra­methyl-6,7,8,9-tetra­hydro-5H-benzocyclo­hepten-7-one

The title compound, C17H22O2, was semi-synthesized from a mixture of α-atlantone (Z) and α-atlantone (E), which were isolated from the essential oil of the Atlas cedar (cedrus atlantica). The mol­ecule consists of fused six- and seven-membered rings. The seven-membered ring is in a screw-boat conformation

A Convergent Synthesis of (�)-?- and ?-Himachalenes

(±)-α and β-Himachalene, 5 and 6, have been synthesized in a convergent manner from 3,3-dimethylacrolein (9), the ester enolate 10 and the silyloxypentadienyllithium 7. The key steps are the regioselective γ-addition of the dienal 13 to 7 and the intramolecular Diels-Alder addition 15 → 16. Hydrogenolysis of the diethylphosphate group and functionalization at C (5) completed the synthesis of 5 and 6.</p