title: Asymmetric total synthesis of the 1-epi-aglycon of the cripowellins A and B.
abstract: [structure: see text] The unusual [5.3.2]-bicyclic structure of the insecticidal Amaryllidaceae alkaloids cripowellin A (1) and B (2) has been synthesized for the first time via a sequence of Sharpless dihydroxylation, ring-closing metathesis, and intramolecular Heck reaction. The asymmetric synthesis of the 1-epi-aglycon 82 proceeds with virtually complete diastereo- and enantioselectivity (de, ee > or = 98%) in 13 steps and an overall yield of 5.6%. In addition, three alternative approaches toward the aglycon 3 are also described focusing on (1) the alkylation of the 2-benzazepinedithianes 35 and 36 with the electrophile 11, (2) a radical cyclization of the precursor (R/S,S,S)-39, and (3) an intramolecular arylation reaction of the aryl ketone 47.
authors.affiliation: Institut für Organische Chemie, RWTH Aachen, Landoltweg 1, 52074 Aachen, Germany. enders@rwth-aachen.de
authors.forename: Dieter
authors.initials: D
authors.lastname: Enders
authors.forename: Achim
authors.initials: A
authors.lastname: Lenzen
authors.forename: Michael
authors.initials: M
authors.lastname: Backes
authors.forename: Carsten
authors.initials: C
authors.lastname: Janeck
authors.forename: Kelly
authors.initials: K
authors.lastname: Catlin
authors.forename: Marie-Isabelle
authors.initials: MI
authors.lastname: Lannou
authors.forename: Jan
authors.initials: J
authors.lastname: Runsink
authors.forename: Gerhard
authors.initials: G
authors.lastname: Raabe
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis; D000478:Alkylation; D047151:Amaryllidaceae Alkaloids / Q000138:chemical synthesis*; D003500:Cyclization; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D047151:Amaryllidaceae Alkaloids; C506143:cripowellin A; C506144:cripowellin B