Citation/Abstract

The total synthesis of cyathin B ₂ and cyathin A ₃ was achieved. The cyathane diterpenoids typically contain a 5,6,7-tricyclic core with the 6,7- trans ring junction. A synthetic challenge lies in the challenging diastereocontrol of the trans ring junction stereochemistry. A Prins-type reaction of a cycloalkenylcyclopropanol silyl ether with an oxocarbenium ion intermediate afforded the spirocyclobutanone adduct. This suitably substituted spirocyclobutanone provided a unique approach to the syntheses of the cyathane diterpenoids in conjunction with a ring closing metathesis reaction.