Highly Efficient Synthesis of the Mannose Nonasaccharide of the N-Glycan Expressed on the HIV Glycoprotein gp 120
作者:Yuliang Zhu、Fanzuo Kong
DOI:10.1055/s-2001-16062
日期:——
A highly concise and effective synthesis of the mannose nonasaccharide of the glycan expressed on the HIV protein gp 120 was achieved via TMSOTf promoted selective 6-glycosylation of a tetrasaccharide 4,6-diol acceptor with a pentasaccharide donor followed by deprotection. The pentasaccharide was constructed by selective 3,6-diglycosylation of 1,2-O-ethylidene-β-d-mannopyranose with 2-O-acetyl-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1 → 2)-3,4,6-O-benzoyl-α-d-mannopyranosyl trichloroimidate while the tetrasaccharide was obtained by selective 3-O-glycosylation of allyl 4,6-O-benzilidene-α-d-mannopyranoside with 2,3,4,6-tetra-O-benzoyl-α-d-mannopyranosyl-(1 → 2)-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1 → 2)-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl trichloroimidate.
通过 TMSOTf 促进四糖-4,6-二醇受体与五糖供体的选择性 6-糖基化,然后进行脱保护,实现了表达在 HIV 蛋白 gp 120 上的甘露糖非异构体的高效简洁合成。五糖是通过 1,2-O-ethylidene-β-d-mannopyranose 与 2-O-acetyl-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1 → 2)-3,4,6-O-benzoyl-α-d-mannopyranosyl trichloroimidate 的选择性 3,6-二糖基化构建的,而四糖则是通过烯丙基 4,6-O-benzilidene-β-d-mannopyranose-(1 → 2)-3,4,6-O-benzoyl-α-d-mannopyranosyl trichloroimidate 的选择性 3-O-糖基化获得的、6-O-二苯甲酰基-δ-d-吡喃甘露糖苷与 2,3,4,6-四-O-苯甲酰基-δ-d-吡喃甘露糖基-(1→2)-3,4,6-三-O-苯甲酰基-δ-d-吡喃甘露糖基-(1→2)-3,4,6-三-O-苯甲酰基-δ-d-吡喃甘露糖基三氯亚氨酸酯进行选择性 3-O-糖基化反应得到四糖。