Trimerization of a steroid ketone to form a chiral molecular cleft

摘要

The acid-catalyzed trimerization of cyclic ketones to give hexasubstituted benzenes has long been known, and various acid catalysts have been employed for this transformation. Unlike the trimerization of alkynes, this triple aldol condensation is inherently directional, and, if an enantiomerically pure starting ketone is used, then only a single, enantiomerically pure, C_3-symmetric product will be obtained. We now show that the trimerizationof steroid ketones with cis A/B ring fusions yields a new class of chiral molecular bowls.