Multicomponent Coupling Approach to (±)-Frondosin B and a Ring-Expanded Analogue

(Equation presented) A recently discovered multicomponent coupling reaction is used to give direct access to a late intermediate in the synthesis of frondosin B. This intermediate can also be efficiently converted to a ring-expanded analogue of frondosin B by sustained heating of the reaction mixture. An unprecedented tandem 1,7-hydrogen shift, 8π-electrocyclization is proposed to explain the formation of this ring-expanded species.