作者:Marion Davoust、Frédéric Cantagrel、Patrick Metzner、Jean-François Brière
DOI:10.1039/b802310g
日期:——
A catalytic diastereoselective sulfonium ylide epoxidation of aldehydes furnished original vinyl epoxides, having an MBH backbone. These highly functionalised building blocks were used for a formal synthesis of the antibiotic conocandin, and opened up a stereodivergent route towards β-hydroxy-α-methylene lactones, core units of naturally occurring compounds. Under acidic conditions, the oxiranes were mainly transformed, with moderate to good yields, into transβ-hydroxy-α-methylene lactones. On the other hand, a user-friendly palladium-catalysed CO2insertion and cyclisation sequence gave the cisβ-hydroxy-α-methylene lactone counterparts along with an interesting cisâtrans equilibration of the Ï-allyl intermediates.
一种催化性的非对映选择性硫镛叶立德环氧化反应,将醛转化为具有MBH骨架的原始乙烯基环氧化物。这些高度功能化的构建块被用于抗生素康索坎丁的正式合成,并开辟了一条向天然化合物核心单元——β-羟基-α-亚甲基内酯的立体发散性途径。在酸性条件下,环氧化物主要发生转化,产率从中等到良好,形成反式β-羟基-α-亚甲基内酯。另一方面,一种用户友好的钯催化CO2插入和环化序列,得到了顺式β-羟基-α-亚甲基内酯及其有趣的π-烯丙基中间体的顺-反平衡。