The synthesis of the suitably protected form (1) of the tetrasaccharide repeat unit, →2)-α-D-Manp-(1→2)-β-D-Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-Manp-(1→ (A), of the O-antigen polysaccharide of the lipopolysaccharide from Escherichia coli O77 has been accomplished by latentactive glycosylation employing the 2′-carboxybenzyl (CB) gly coside method. In addition to previously used latent glycosyl donors, 2′-(benzyloxycarbonyl)benzyl (BCB) glycosides, new latent glycosyl donors, 2'-(allyloxycarbonyl)benzyl (ACB) glycosides, have been introduced as a direct precursor for the active CB glycosides. We also demonstrate that 4,6-O-benzylidene-2-azido-2-deoxy-α-D-mannopyranoside (7) has been readily prepared from D-glucosamine in good yield.Key words: Escherichia coli O77, glycosylation, 2′-carboxybenzyl (CB) glycosides, 2′-(allyloxycarbonyl)benzyl (ACB) glycosides, glycosyl donor.
大肠杆菌 O77 脂多糖的 O 型抗原多糖的适当保护形式(1),即 →2)-α-D-Manp-(1→2)-β-D-Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-Manp-(1→ (A)、大肠杆菌 O77 脂多糖的 O 型抗原多糖是通过 2′-羧基苄基(CB)糖苷法进行潜伏糖基化完成的。除了以前使用过的潜在糖基供体 2′-(苄氧羰基)苄基(BCB)糖苷外,我们还引入了新的潜在糖基供体 2'-(烯丙氧羰基)苄基(ACB)糖苷,作为活性 CB 糖苷的直接前体。我们还证明,4,6-O-亚苄基-2-叠氮-2-脱氧-α-D-吡喃甘露糖苷(7)很容易从 D-氨基葡萄糖中制备出来,而且收率很高:大肠杆菌 O77 糖基化 2′-羧基苄基(CB)糖苷 2′-(烯丙氧羰基)苄基(ACB)糖苷 糖基供体