Completely β-Selective Glycosylation Using 3,6-<i>O</i>-(<i>o</i>-Xylylene)-Bridged Axial-Rich Glucosyl Fluoride
作者:Yasunori Okada、Noriaki Asakura、Masafumi Bando、Yoshiki Ashikaga、Hidetoshi Yamada
DOI:10.1021/ja301480g
日期:2012.4.25
A completely β-selective glycosylation that does not rely on neighboring group participation is described. The novelty of this work is the design of the glycosyl donor locked into the axial-rich form by the o-xylylene bridge between the 3-O and 6-O of d-glucopyranose. The synthesized 2,4-di-O-benzyl-3,6-O-(o-xylyene)glucopyranosyl fluoride could efficiently react with various alcohols in a SnCl(2)-AgB(C(6)F(5))(4)
描述了一种不依赖于相邻基团参与的完全 β 选择性糖基化。这项工作的新颖之处在于设计的糖基供体通过 d-吡喃葡萄糖的 3-O 和 6-O 之间的邻二甲苯桥锁定为富含轴向的形式。合成的 2,4-di-O-benzyl-3,6-O-(o-xylyene) 吡喃葡萄糖基氟可以有效地与 SnCl(2)-AgB(C(6)F(5))( 4)催化体系。通过使用酸性和碱性分子筛的比较实验揭示了由糖基化和异构化循环组成的机制。实现的完美立体控制归因于富含轴向的构象和由原位生成的 HB(C(6)F(5))(4) 引起的收敛异构化的协同作用。