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The spiroenone (7), stereoselectively prepared from (+)-p-menth-1-ene (3) in four steps, was converted by two different reaction sequences into the natural sesquiterpenes (–)-acorenone (1) and (–)-acorenone B (2), respectively, thus establishing the absolute configuration of (1).

The spiroenone (7), stereoselectively prepared from (+)-p-menth-1-ene (3) in four steps, was converted by two different reaction sequences into the natural sesquiterpenes (–)-acorenone (1) and (–)-acorenone B (2), respectively, thus establishing the absolute configuration of (1).

The ketone (2), obtained from racemic α-terpineol (3), was converted by a six-step sequence into the 2-formyl-cyclohexadienone (14) which reacted stereoselectively with several methylcuprates, possibly by formation of an intermediate of type (16); e.g. with the lithium methylbromocuprate-di-isobutylamine complex a 5 : 1 mixture of racemic β-vetivone (1) and 10-epi-β-vetivone (12) was obtained, after deformylation.