A convergent approach to the synthesis of the biologically active diterpenoid clerodane and ent-clerodane natural products is described. Some of them have been shown to be potent insect antifeedants. Others have been found to possess antitumor, antimicrobial, antifungal, antiviral, or antiulcer activity. The key intramolecular cycloaddition controls the stereochemistry of four contiguous asymmetric centers of the clerodane skeleton. The route allows for the selective introduction or removal of oxygen functionality, depending on the nature of the final target. The proposed synthesis of bacchofertin serves to demonstrate the feasibility of the approach.
