Department of Chemistry, Jadavpur University , Kolkata 700 032, India.
J Org Chem. 2017 Jun 2;82(11):5751-5760. doi: 10.1021/acs.joc.7b00561. Epub 2017 May 18.
Concise syntheses of the acidic pentasaccharide, related to the O-antigenic polysaccharide of Escherichia coli 120, as its p-methoxyphenyl glycoside, have been achieved using a one-pot sequential glycosylation technique. The glycosylations have been accomplished either by the activation of the thioglycosides using NIS in the presence of FeCl or by a preactivation by PhSO, TTBP, TfO, and the activation of the trichloroacetimidates using FeCl alone or TMSOTf. Most of the intermediate steps are high yielding, and the stereo outcomes of the glycosylation steps were excellent. The syntheses of the targeted pentasaccharide have been performed with both three- and four-component, one-pot sequential glycosylation reactions, and in both cases, the orthogonal glycosylations are carried out utilizing catalytic activity of FeCl. A late-stage TEMPO-mediated regioselective oxidation has been performed to achieve the required uronic acid motif.
已经使用一锅顺序糖苷化技术实现了酸性五糖的简洁合成，该五糖与大肠杆菌 120 的 O-抗原多糖有关，其为对甲氧基苯苷。糖苷化可以通过 NIS 在 FeCl 的存在下激活硫代糖苷，或者通过 PhSO2，TTBP，TfO 的预激活以及单独使用 FeCl 或 TMSOTf 激活三氯乙酰亚胺酯来完成。大多数中间步骤具有高产率，并且糖苷化步骤的立体化学结果非常出色。使用三组分和四组分一锅顺序糖苷化反应进行了目标五糖的合成，在这两种情况下，正交糖苷化都利用 FeCl 的催化活性进行。进行了晚期阶段的 TEMPO 介导的区域选择性氧化，以实现所需的糖醛酸基序。
