Total Syntheses of (+)-Polygalolide A and (+)-Polygalolide B: Elucidation of the Absolute Stereochemistry and Biogenetic Implications
作者:Yukihito Sugano、Fumiaki Kikuchi、Akinori Toita、Seiichi Nakamura、Shunichi Hashimoto
DOI:10.1002/chem.201200542
日期:2012.7.27
carbonyl ylide formation/intramolecular 1,3‐dipolar cycloaddition sequence. The arylmethylidene moiety of these natural products was successfully installed by a Mukaiyama aldol‐type reaction of a silyl enol ether with a dimethyl acetal, followed by elimination under basic conditions. We have also developed an alternative approach to the carbonyl ylide precursor based on a hetero‐Michael reaction. This approach
(+)-聚没食子内酯A和(+)-聚没食子内酯B的总合成已通过使用羰基内酯环加成策略完成。通过[Rh 2(OAc)4]催化的羰基叶立德形成/分子内1,3-偶极环加成序列。这些天然产物的芳基亚甲基部分是通过甲硅烷基烯醇醚与二甲基乙缩醛的Mukaiyama aldol型反应成功安装的,然后在碱性条件下消除。我们还开发了一种基于杂-迈克尔反应的羰基叶立德前体的替代方法。该方法需要18个步骤,天然产物的总收率为9.8%和9.3%。比较合成材料和天然产物的比旋光度,表明聚果糖苷是通过果糖衍生的氧pyryrylium两性离子与异戊二烯衍生物之间的[5 + 2]环加成而以几乎外消旋的形式生物合成的。