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).

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