title: Addition of organometallic reagents to chiral N-methoxylactams: enantioselective syntheses of pyrrolidines and piperidines.
abstract: Enantioselective iridium-catalyzed allylic substitutions were used to prepare N-allyl hydroxamic acid derivatives that were suitable for ring-closing metathesis, giving N-methoxylactams. Reactions of these derivatives with Grignard or organolithium compounds gave hemiaminals, which could be reduced diastereoselectively via acyliminium intermediates to give cis-piperidines or cis-pyrrolidines with substituents in the 2,6- or 2,5-positions, respectively. In addition, compounds with a quaternary carbon center could be synthesized by corresponding reactions with potassium cyanide/AcOH. The procedures were applied in the syntheses of alkaloids (-)-209D and (+)-prosophylline.
authors.affiliation: Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 6221-544205.
authors.forename: Mascha
authors.initials: M
authors.lastname: Jäkel
authors.forename: Jianping
authors.initials: J
authors.lastname: Qu
authors.forename: Tobias
authors.initials: T
authors.lastname: Schnitzer
authors.forename: Günter
authors.initials: G
authors.lastname: Helmchen
keywords: alkaloids; allylic compounds; enantioselectivity; iridium; lactams