An expeditious and enantioselective entry to the ABC ring of the quassinoid skeleton
Abstract
The tricycle (5) with two trans-fused angular methyl groups is constructed from tiglic aldehyde and (S)-carvone involving a stereocontrolled aldol reaction and an endo-selective intramolecular Diels–Alder (IMDA) reaction; the stereochemistry was established by an X-ray study.