Remarkable stereoselectivity in the alkylation of a hydroazulenone: progress towards the total synthesis of guanacastepene

exo-Methylene ketone 6 serves as a vehicle for elaboration of the C8 quaternary center en route to guanacastepene via a conjugate addition–alkylation sequence. Methylation of the cycloheptadienolate derived from 7 is highly selective for the desired relative stereochemistry, as determined by NMR and crystallographic analysis.