A stereodivergent synthesis of beta-hydroxy-alpha-methylene lactones via vinyl epoxides.
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.
Davoust
Marion
M
Laboratoire de Chimie Moléculaire et Thio-organique, ENSICAEN, Université de Caen, CNRS, 6 Boulevard du Maréchal Juin, 14050 Caen, France.
Cantagrel
Frédéric
F
Metzner
Patrick
P
Brière
Jean-François
JF
D004852:Epoxy Compounds / Q000737:chemistry*; D007783:Lactones / Q000138:chemical synthesis*; D013237:Stereoisomerism
D004852:Epoxy Compounds; D007783:Lactones