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.

Citation

Marion Davoust, Frédéric Cantagrel, Patrick Metzner, Jean-François Brière. A stereodivergent synthesis of beta-hydroxy-alpha-methylene lactones via vinyl epoxides. Organic & biomolecular chemistry. 2008 Jun 7;6(11):1981-93

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PMID: 18480914

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