Synthesis of oligosaccharides corresponding to Vibrio cholerae O139 polysaccharide structures containing dideoxy sugars and a cyclic phosphate
作者:Dominika Turek、Andreas Sundgren、Martina Lahmann、Stefan Oscarson
DOI:10.1039/b518125a
日期:——
oside, a thioglycoside tetrasaccharide donor block was constructed through two orthogonal glycosylations with glycosyl bromide donors. First, a properly protected galactose moiety was introduced using silver triflate as promoter and subsequently the two colitose residues, carrying electron-withdrawing protecting groups for stability reasons, under halide-assisted conditions. The tetrasaccharide block
带有间隔基的四糖,对氨基环己基乙基α-1-Colp-(1-> 2)-β-d-Galp-(1-> 3)-[α-1-Colp-(1-> 4) )]-β-D-GlcpNAc,在半乳糖残基中含有4,6-环磷酸酯,已经合成。该结构对应于地方性细菌O139型霍乱弧菌同义词孟加拉的荚膜(和脂)多糖的重复单元的一部分。合成策略允许连续合成完整的O139六糖重复单元以及血清型O22的结构相关重复单元。从乙基2-叠氮基-4,6-O-亚苄基-2-脱氧-1-硫代-β-D-吡喃葡萄糖苷开始,通过与糖基溴化物供体的两个正交糖基化来构建硫糖苷四糖供体嵌段。第一的,使用三氟甲磺酸银作为促进剂引入适当保护的半乳糖部分,然后在卤化物辅助条件下,出于稳定性原因,携带携带吸电子保护基团的两个大肠菌残基引入。然后将四糖嵌段以NIS-TMSOTf促进的偶联方式连接至间隔基。使用H2S将叠氮基团转化为乙酰氨基基团,然后除去临时的保护性