Gold-catalyzed alkyne-diol bicycloketalization enables enantioselective divergent total syntheses of attenols

Abstract

Gold-catalyzed bicycloketalization of alkyne-diols provides synthetic advantages when compared to that of keto-diols under acidic conditions. The relative inertness of the alkyne moiety compared to that of the ketone group provided us with strategic flexibility that enabled orthogonal protecting group manipulation of five hydroxyl groups during the total syntheses of attenols. Herein, we describe our newly developed divergent synthetic route to attenols A and B, isomers with distinct bicyclic ketal cores, that was enabled by gold-catalyzed ketalization. Our total synthesis of attenols A and B overcomes the issue of isomerization between these two natural products.