Vinyl Carbanions. Part 36.. Synthesis of 3-deoxy-D-manno-2-octulosonic acid (KDO) and derivatives
作者:Angelika Esswein、Rainer Betz、Richard R. Schmidt
DOI:10.1002/hlca.19890720205
日期:1989.3.15
β-C-lithiated acrylamide 3A has been proven to be an ideal pyruvate β-carbanion equivalent useful in a highly diastereoselective KDO synthesis. The starting material 3 was prepared from pyruvate diethyl acetal in four convenient steps. Direct lithiation with 2 equiv. of LDA generated the dilithiated species 3A quantitatively. Reaction with 2,3:4,5-di-O-isopropylidene-D-arabinose (11) was highly D-manno-selective
所述β- Ç -lithiated丙烯酰胺3A已被证明是一种理想的丙酮酸β负离子等效有用以高度非对映KDO合成。在四个方便的步骤中由丙酮酸二乙缩醛制备原料3。具有2当量的直接锂化。LDA的量定量地产生了双锂化的物质3A。与2,3:4,5-二-O-异亚丙基-D-阿拉伯糖(11)的反应是高度D-甘露糖选择性的。通过结晶容易地从反应混合物中获得产物12。闭环丁烯内酯13,随后用Bu去除PhS-基3 SnH和吡啶鎓溴化物,通过氢解脱苄基作用得到已知的丁烯内酯19。此KDO前驱物通过两个方便的步骤提供了KDO。丁烯内酯19也通过两个高产率步骤转化为4,5:7,8-二-O-环己叉基-KDO衍生物22,这是KDOα-糖苷合成的重要原料。