Synthetic studies toward cyathin diterpenoids: approach to the tricyclic system through intramolecular Heck-type cyclization

The enantioselective synthesis of a model of the core ring system of cyathin diterpenes is described. The key tricyclic acetate 4 was assembled via an intramolecular Heck-type cyclization of the chiral triflate 8. Acetate 4 was taken through to model cyathan ketones 3a and 3b by a one-carbon ring expansion.