Asymmetric Total Synthesis of Shagenes A and B

Abstract We report the first total synthesis of shagenes A and B, which are tricyclic terpenoids containing a cis ‐substituted cyclopropane, via ring‐closing metathesis of an enamide and Ir‐catalyzed double‐bond isomerization of an alkylidenecyclopropane. Chemo‐ and diastereoselectivity in the distorted cis ‐substituted structures were controlled by the alkylidenecyclopropane reactivity and using the ketone functionality as a remote directing group for the Ir catalyst, respectively. The total synthesis suggested the absolute configuration of shagenes.