Synthesis of sesquiterpene allylic alcohols and sesquiterpene dienes from Cupressus bakeri and Chamaecyparis obtusa

Five muurolane (1–5), one nor-seco-muurolane (6) and one nor-muurolane (7) sesquiterpene natural products recently reported from Cupressus bakeri have been obtained by chemical synthesis together with the unnatural 7-epimeric amorphane analogues of four of these sesquiterpenes (15, 16, 18 and 19). The conversion of sesquiterpene allylic tertiary alcohols 1, 2, 15 and 16 into regioisomeric sesquiterpene dienes 3–5 and 17–20 was investigated in vitro by NMR and the mechanism for such dehydrations and their relevance to the origins of sesquiterpene dienes which have been reported as natural products (such as 3–5) is discussed.