Stereoselective synthesis of eremophilane sesquiterpenoids from β‐pinene

Abstract 2‐Methyl‐4‐isopropylidenecyclohexanone (7) can be obtained in good yield from β‐pinene (2) in a 5‐step sequence. Key step is the acid‐catalysed ring opening of cis ‐3‐methylnopinone (5) to give 4‐(l′‐hydroxyisopropyl)‐2‐methylcyclohexanone (6, XOH). Robinson annulation of 7 with trans ‐3‐penten‐2‐one proceeds stereoselectively to give α‐vetivone (10). Similar annulation of the isopropenyl isomer (8) affords 7‐ epi ‐nootkatone (11). 10 can be converted in good yield to nootkatone (13).