Total Synthesis of (+)-Isolaurepinnacin. Use of Acetal-Alkene Cyclizations To Prepare Highly Functionalized Seven-Membered Cyclic Ethers
作者:Daniel Berger、Larry E. Overman、Paul A. Renhowe
DOI:10.1021/ja964080b
日期:1997.3.1
The first synthesis of the title compound is described. The synthesis features an acetal-vinylsilane cyclization to stereoselectively form the cis-2,7-disubstituted oxepene ring and introduce Δ4 unsaturation. Starting with (2R,3S)-2,3-epoxypentan-1-ol (16), mixed acetal 10 is formed in five steps and 72% overall yield. Treatment of 10 with excess BCl3 in CH2Cl2 at −78 → 0 °C promotes cyclization to
描述了标题化合物的第一次合成。该合成采用乙缩醛-乙烯基硅烷环化以立体选择性地形成顺式-2,7-二取代的氧杂环戊烯环并引入 Δ4 不饱和度。从 (2R,3S)-2,3-epoxypentan-1-ol (16) 开始,混合缩醛 10 分五步形成,总产率为 72%。在-78 → 0 °C 的 CH2Cl2 中用过量 BCl3 处理 10 促进环化,在甲硅烷基醚脱保护后以 90% 的产率提供 Δ4-oxepene 39。六碳侧链的 (E)-烯炔官能团的精心设计完成了 (+)-异紫杉醇的合成。