Asymmetric synthesis of the tetracyclic core of bufogargarizin C by an intramolecular [5 + 2] cycloaddition

Abstract

A concise asymmetric synthesis of the core of bufogargarizin C, which contains a synthetically challenging 7/5/6/5-tetracyclic ring system, is reported. This approach features a unique Brønsted acid-mediated intramolecular [5 + 2] cycloaddition, which is the first example of intramolecular [5 + 2] cycloaddition of an allene moiety mediated by acid.