title: A dirhodium(II)-carbenoid route to (-)- and (+)-Geissman-Waiss lactone: synthesis of (1R,7R,8R)-(-)-turneforcidine.
abstract: (-)- and (+)-Geissman-Waiss lactone, 4b, was efficiently prepared via the intramolecular C-H insertion reaction of the chiral nonracemic diazoacetates (-)-5a and (+)-5b catalyzed by dirhodium(II) tetrakis[methyl (5R and 5S)-3-phenylpropanoyl-2-imidazolidinone-5-carboxylate]. The cyclization was found to proceed with excellent regioselectivity and cis-diastereoselectivity. The bicyclic lactone (-)-4b was successfully used in the synthesis of the necine base, (-)-turneforcidine 2.
authors.affiliation: Department of Chemistry and Biochemistry, University of Regina, Regina, Saskatchewan, S4S 0A2, Canada. Andrew.Wee@uregina.ca
authors.forename: A G
authors.initials: AG
authors.lastname: Wee
mesh_terms: D002384:Catalysis; D007783:Lactones / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010946:Plants, Medicinal / Q000737:chemistry; D011763:Pyrrolizidine Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D012238:Rhodium; D013237:Stereoisomerism
chemical_list: C443725:Geissman-Waiss lactone; D007783:Lactones; D011763:Pyrrolizidine Alkaloids; C443726:turneforcidine; D012238:Rhodium