Construction of All-cis-substituted Cyclopropane and Total Synthesis of Avenaol

Abstract

The first total synthesis of avenaol was achieved using a new robust strategy involving all-cis-substituted cyclopropane formation via an alkylidene cyclopropane. The keys to success for the total synthesis were (i) Rh-catalyzed intramolecular cyclopropanation of an allene; (ii) Ir-catalyzed stereoselective double-bond isomerization to form an all-cis cyclopropane; and (iii) differentiation of two hydroxymethyl groups via regioselective cyclization and oxidation of tetrahydropyran based on the reactivity of cyclopropyl group. This strategy effectively avoids cyclopropane ring opening and undesired formation of a cage structure. Additionally, the proposed structure of avenaol, especially unique all-cis-substituted cyclopropane was confirmed correct by this total synthesis.