摘要:
Cyclization of (5-N-pyrrolyl-2-hydroxypentyl)cobaloxime (13) proceeds by intramolecular electrophilic aromatic substitution of a cobaloxime pi-cation onto the pyrrole ring to provide 6-exo cyclization product (14) in 95% yield. This cyclization is highly enantioselective. It is applied to a synthesis of highly enantioenriched (-)-tashiromine, (-)-21, and a formal synthesis of (+)-tashiromine. (C) 1997 Elsevier Science Ltd.