A convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of the verotoxin producing E. coli O176 has been achieved in excellent yield adopting a [2 + 2] block glycosylation strategy. The β-D-mannosidic moiety of the tetrasaccharide was prepared from β-D-glucoside and α-D-galactosamine moiety was derived from D-galactal. The tetrasaccharide was synthesized as its 2-trimethylsilylethyl glycoside in excellent yield. All intermediate steps are high yielding.
采用[2 + 2]嵌段糖基化策略,以极高的收率合成了产verotoxin大肠杆菌O176的O抗原的四糖重复单元。四糖中的β-
D-甘露糖苷分子是由β-
D-葡萄糖苷制备的,而α-
D-半乳糖胺分子则来自
D-半乳糖醛。四糖以其 2-三甲基
硅乙基糖苷的形式合成,收率极高。所有中间步骤的产量都很高。