Synthesis of the Tetracyclic ABCD Ring Domain of Calyciphylline A-Type Alkaloids via Reductive Radical Cyclizations.
Guilhem CoussanesJosep BonjochPublished in: Organic letters (2017)
A tetracyclic compound with the ABCD ring framework of calyciphylline A-type alkaloids was synthesized from a cis-3a-methyloctahydroindole triggered by a 5-endo radical cyclization. The synthesis required two additional ring-forming steps: the construction of a seven-membered ring by aldol cyclization and the azabicyclic fragment by a radical ring closure of a trichloroacetamide-tethered enol acetate followed by a diastereoselective α-methylation of the lactam group.