Convergent, Enantioselective Syntheses of Guanacastepenes A and E Featuring a Selective Cyclobutane Fragmentation<sup>1</sup>
作者:William D. Shipe、Erik J. Sorensen
DOI:10.1021/ja060847g
日期:2006.5.1
of a convergent strategy that led to efficient, enantioselective syntheses of both natural (+)- and unnatural (-)-guanacastepene E and formal total syntheses of (+)- and (-)-guanacastepene A is described. A union of five- and six-membered ring intermediates by an efficient pi-allyl Stille cross-coupling reaction was followed by an intramolecular enone-olefin [2 + 2] photocycloaddition and a stereoelectronically
描述了导致天然 (+)- 和非天然 (-)-guanacastepene E 的高效、对映选择性合成以及 (+)- 和 (-)-guanacastepene A 的正式全合成的收敛策略的演变。通过有效的π-烯丙基Stille 交叉偶联反应将五元和六元环中间体结合起来,然后进行分子内烯酮-烯烃[2 + 2] 光环加成和立体电子控制的还原性裂解,生成环丁基酮。后两种转变能够控制形成 C-11 四元立体中心和 guanacastepenes 的中央七元环。还开发了从单萜 R-(-)-香芹酮对功能化五元环乙烯基锡烷的对映特异性合成,其特征是碳-碳键形成环收缩。