Contribution to the chemistry of β-pipitzol

Exploration of the chemistry of β-pipitzol (1a) leads to the preparation of a series of new derivatives, thus allowing its correlation with ent-3-epi-a-cedrene (18) known as 3-epi-α-cedrene. Alcohol 2, obtained by LiAlH₄reduction of O-methyl-β-pipitzol (1c), undergoes 1–4 dehydration on acid treatment, giving the ketoalcohol 3, which differs only in the stereochemistry at C-9 from the ketoalcohol 4a obtained by Li/NH₃ reduction of lc, followed by acid treatment. Moreover, hydrolysis of 4-desoxo-β-pipitzol benzoate (12) and of 4, 9-bis-desoxo-β-pipitzol benzoate (15) yields ketones 10 and 16, respectively, which differ in the stereochemistry of the methyl group at C-6. Catalytic hydrogenation of ketoalcohol 3 followed by oxidation gave the diketone 9, which is epimeric at C-6 with the diketone 10, its stereochemistry being deduced from ord measurements. Spectroscopic data and stereochemical assignment for all compounds are provided.