Synthetic studies toward the cytotoxic norditerpene (+)-harringtonolide: setting up key-stereogenic centers of the cyclohexane ring D
作者:Hajer Abdelkafi、Laurent Evanno、Patrick Herson、Bastien Nay
DOI:10.1016/j.tetlet.2011.04.101
日期:2011.7
(+)-harringtonolide were installed by functionalization of an enantiomerically pure IMDA cycloadduct, constructed from the chiral pool. The chiral 1,3-dioxane template used to direct the IMDA reaction was unraveled in an acidic medium, through spectacular hydrolysis of the acetal and concomitant lactone ring contraction. The central cyclohexene was selectively epoxidized either on the β- or on the α-side
(+)-harringtonolide不对称循环D的关键立体生成中心是通过手性池中构建的对映体纯IMDA环加合物的功能化安装的。通过缩醛的惊人水解和伴随的内酯环收缩,在酸性介质中解开了用于指导IMDA反应的手性1,3-二恶烷模板。取决于取代方式,中央环己烯在β-侧或α-侧上选择性地环氧化。几种环氧化物中间体的反应性受到了harringtonolide氧化桥的构建的挑战。我们发现其中一种适合获取另一种天然产品四溴新霉素,其与harringtonolide具有相似的替代方式。另外,功能化导致建立关键立体中心,在途中合成了harringtonolide的不对称合成。环氧中间体的反应性为该全合成的未来工作提供了有益的见识。