Enantioselective total synthesis of (+)-ibophyllidine via an asymmetric phosphine-catalyzed [3 + 2] annulation.
In this study we performed the total synthesis of the terpene indole alkaloid (+)-ibophyllidine through a pathway involving asymmetric phosphine catalysis, with our novel l-4-hydroxyproline-derived chiral phosphine mediating the key [3 + 2] annulation. Hydrogenation of the [3 + 2] adduct allowed the rapid formation of the stereochemically dense pyrrolidine ring of (+)-ibophyllidine in excellent yield with exceptionally high levels of both diastereo- and enantioselectivity. We constructed the remainder of the pentacyclic skeleton through an intramolecular alkylation and an intramolecular aza-Morita-Baylis-Hillman reaction.
Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.
Ian P
IP
Andrews
Ohyun
O
Kwon