title: A stereodivergent synthesis of beta-hydroxy-alpha-methylene lactones via vinyl epoxides.
abstract: A catalytic diastereoselective sulfonium ylide epoxidation of aldehydes furnished original vinyl epoxides, having an MBH backbone. These highly functionalized building blocks were used for a formal synthesis of the antibiotic conocandin, and opened up a stereodivergent route towards beta-hydroxy-alpha-methylene lactones, core units of naturally occurring compounds. Under acidic conditions, the oxiranes were mainly transformed, with moderate to good yields, into trans beta-hydroxy-alpha-methylene lactones. On the other hand, a user-friendly palladium-catalysed CO2 insertion and cyclisation sequence gave the cis beta-hydroxy-alpha-methylene lactone counterparts along with an interesting cis-trans equilibration of the pi-allyl intermediates.
authors.affiliation: Laboratoire de Chimie Moléculaire et Thio-organique, ENSICAEN, Université de Caen, CNRS, 6 Boulevard du Maréchal Juin, 14050 Caen, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Davoust
authors.forename: Frédéric
authors.initials: F
authors.lastname: Cantagrel
authors.forename: Patrick
authors.initials: P
authors.lastname: Metzner
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Brière
mesh_terms: D004852:Epoxy Compounds / Q000737:chemistry*; D007783:Lactones / Q000138:chemical synthesis*; D013237:Stereoisomerism
chemical_list: D004852:Epoxy Compounds; D007783:Lactones