Organic Chemistry Department, Universidade de Vigo, Lagoas-Marocosende s/n, 36310 Vigo (Spain).
Chemistry. 2013 Sep 23;19(39):13065-74. doi: 10.1002/chem.201301873. Epub 2013 Aug 12.
A new stereocontrolled total synthesis of the configurationally labile C37 -norcarotenoid pyrrhoxanthin in enantiopure form has been completed. A highly stereoselective Horner-Wadsworth-Emmons (HWE) condensation of a C17-allylphosphonate and a C20-aldehyde was used as the last conjunctive step. Both a Sonogashira reaction to form the C17-phosphonate and the final HWE condensation proved to be compatible with the sensitive C7-C10 enyne E configuration. Regioselective (5-exo-dig) silver-promoted lactonization reactions of three alternative pent-2-en-4-ynoic acid precursors with increased complexity, including a fully functionalized C20-fragment, were explored for the preparation of the γ-alkylidenebutenolide fragment. This survey extends the existing methodologies for the preparation of oxygen-containing carotenoids (xanthophylls) and streamlines the synthesis of additional members of the C37-norcarotenoid butenolide family of natural products.
已完成具有构象不稳定 C37-类胡萝卜素吡咯并叶黄素的对映体纯全新的立体控制全合成。最后连接步骤采用高度立体选择性的 Horner-Wadsworth-Emmons（HWE）缩合反应，由 C17-烯丙基膦酸酯和 C20-醛组成。Sonogashira 反应形成 C17-膦酸酯和最终的 HWE 缩合都被证明与敏感的 C7-C10 烯炔 E 构型兼容。探索了三种具有增加复杂性的替代戊-2-烯-4-炔酸前体的区域选择性（5-exo-dig）银促进内酯化反应，包括全功能化的 C20-片段，以制备γ-烷基烯丁烯内酯片段。该调查扩展了含氧类胡萝卜素（叶黄素）的现有制备方法，并简化了 C37-类胡萝卜素丁烯内酯天然产物家族的其他成员的合成。
