Enantioselective Total Syntheses of Lyconadins A-E through a Palladium-Catalyzed Heck-Type Reaction.

A novel palladium-catalyzed Heck-type reaction of thiocarbamates has been designed to construct bridged seven-membered-ring systems that are otherwise challenging to prepare. Taking advantage of this newly developed method, enantioselective syntheses of lyconadins A-E (1-5), lycopecurine (6), and dehydrolycopecurine (7) have been realized in a divergent fashion. Our synthetic strategy also features an intramolecular cyclization of a N-chloroamine to forge the C6-N bond, a transannular Mannich-type reaction of a cyclic nitrone to stitch the C4 and C13 together, and a cyclocondensation to deliver the (dihydro-)pyridone motif.