Stereocontrolled Synthesis of a C<i><sup>n</sup></i>-C<i><sup>n</sup></i><sup>+7</sup>Building Block (“Eastern Moiety”) for the Unnatural Enantiomers of Important Polyol,Polyene Antibiotics Based on a Ring-Closing Metathesis and an Aldol Addition of a Lactone Enolate
作者:Sonja B. Kamptmann、Reinhard Brückner
DOI:10.1002/ejoc.201300183
日期:2013.10
A stereocontrolled synthesis of epoxide 6, which represents the Cn–Cn+7 or “eastern moiety” building block for the title compounds, has been realized in 19 steps. Our synthesis started from tetrabromoacetone 26 and afforded dibromotriene 33b in six steps. The latter was subjected to a ring-closing metathesis, which gave the dibromovinyl-substituted lactone 34 in high yield. A highly stereoselective
环氧化物 6 的立体控制合成,代表标题化合物的 Cn–Cn+7 或“东部部分”构建块,已通过 19 个步骤实现。我们的合成从四溴丙酮 26 开始,分六步得到二溴三烯 33b。后者进行闭环复分解,以高产率得到二溴乙烯基取代的内酯34。高度立体选择性的共轭添加/烯醇醛醇化序列以完美的选择性建立了额外的立体中心。环氧化物 47b 在另外八个步骤中达到,其中包括在缩醛基团存在下的 C-SiMe2Ph → C-OH 氧化。最终的结构 6 通过氢甲酰化/溴化作用完成。