Abstract
A 12-step synthesis of 26, the functionalized hydroazulenone ring of guanacastepene (1), has been completed using the EtAlCl2-initiated cyclization of γ,δ-unsaturated ketone 13 to construct 2,2,3-trisubstituted cyclopentanone 14, the palladium-catalyzed coupling of vinylmagnesium bromide with enol triflate 17 to prepare triene 21, and olefin metathesis of triene 21 to form the key hydroazulene 20.