Synthesis of Cyathin A₃ and Cyathin B₂

Significance

A stereoselective synthesis of cyathin B₂ and cyathin A₃ depicted here is noteworthy for a Prins reaction of vinylcyclopropanol B to afford the spirocyclobutanone D which served as a convenient scaffold for the stereoselective formation of a functionalized seven-membered ring via a ring-closing metathesis (D → G).