Synthetic studies on the preparation of oxygenated spongiane diterpenes from carvone

The paper describes a new diastereoselective approach to oxygenated spongiane diterpenes functionally related to natural dorisenones. The strategy followed for the preparation of the spongiane framework, a B→AB→ABC→ABCD approach, is based on the preparation of epoxydecalone (AB rings) from R-(−)-carvone, followed by an intramolecular Diels–Alder reaction for the construction of the C ring (compound ). Further manipulation of the Diels–Alder adduct functionality allows the completion of the spongiane framework and the elaboration of several oxygenated spongiane-type compounds. The structures of two compounds and , has been established by single-crystal X-ray crystallography.