Diastereo- and Enantioselective Synthesis ofN-Protected 2-Amino 1,4-Diols by an Oxa Michael Addition/1,3-Dipolar Cycloaddition Protocol
作者:Dieter Enders、Andreas Haertwig、Jan Runsink
DOI:10.1002/(sici)1099-0690(199809)1998:9<1793::aid-ejoc1793>3.0.co;2-9
日期:1998.9
diastereoselective inter- and intramolecular 1,3-dipolar cycloaddition reaction of optically active nitrile oxides as a key step. The nitro alkane starting materials were obtained by diastereoselective oxa Michael addition of (1R,2S)-(–)-N-formylnorephedrine (1) to aliphatic (E)-nitro alkenes 2, 6a, b (de = 96 – ≥ 98%). Subsequent diastereo- and regioselective cycloaddition reactions to highly substituted 4,5-isoxazolines
N-保护的氨基二醇的对映选择性合成已通过采用光学活性腈氧化物的非对映选择性分子间和分子内 1,3-偶极环加成反应作为关键步骤来完成。通过 (1R,2S)-(–)-N-甲酰基去甲麻黄碱 (1) 与脂肪族 (E)-硝基烯烃 2, 6a, b (de = 96 – ≥ 98%) 的非对映选择性氧杂迈克尔加成获得硝基烷烃原料)。随后对高度取代的 4,5-异恶唑啉 5a-e、8a、b (52-81%) 和还原性开环的非对映和区域选择性环加成反应 - 在辅助剂裂解后 - 以良好的总产率生成氨基二醇 13、14 (27-40%,超过 5 个步骤)并且具有出色的非对映体和对映体过量(de,ee ≥ 96%)。