title: New asymmetric approach to natural pyrrolizidines: synthesis of (+)-amphorogynine A, (+)-amphorogynine D, and (+)-retronecine.
abstract: Three natural pyrrolizidines, (+)-amphorogynines A and D and (+)-retronecine, have been prepared from a common lactam intermediate. This central compound, in turn, was synthesized in diastereomerically enriched form through a highly selective [2 + 2]-cycloaddition of dichloroketene with a chiral enol ether, followed by Beckmann ring expansion and reduction. Subsequent stereocenters were then cleanly introduced through internal induction.
authors.affiliation: Université Joseph Fourier de Grenoble, Chimie Recherche (LEDSS), 38041 Grenoble Cedex, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Roche
authors.forename: Katarína
authors.initials: K
authors.lastname: Kadlecíková
authors.forename: Amaël
authors.initials: A
authors.lastname: Veyron
authors.forename: Philippe
authors.initials: P
authors.lastname: Delair
authors.forename: Christian
authors.initials: C
authors.lastname: Philouze
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Greene
authors.forename: David
authors.initials: D
authors.lastname: Flot
authors.forename: Manfred
authors.initials: M
authors.lastname: Burghammer
mesh_terms: D015394:Molecular Structure; D011763:Pyrrolizidine Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D011763:Pyrrolizidine Alkaloids; C476522:amphorogynine A; C511254:amphorogynine D; C014795:retronecine