Intramolecular Heck cyclization of α-sulfenyl enol triflates. Asymmetric synthesis of a pentacyclic cardenolide precursor having functionality at C-11

Article abstract of DOI:10.1016/S0040-4039(98)00860-0

A concise route to the core of complex cardenolides is described. The sequence features use of a sulfone to join enantioenriched A and D ring fragments and also control intramolecular aldolization to generate ring C and an intramolecular Heck cyclization of an α-sulfenyl enol triflate to form the steroid skeleton.