The total synthesis of the oligosaccharide moiety of disialosyl globopentaosylceramide (DSGb5 Cer), a dominant ganglioside isolated from malignant renal cell carcinoma tissues, is reported. The synthetic strategy relies on a chemical α(2,6)-sialylation at the internal GalNAc unit of a Gb5 pentasaccharide backbone that furnishes a Neu5Acα(2,6)GalNAc-linked hexasaccharide, suitable for an enzymatic α(2,3)-sialylation of the terminal Gal residue to construct a heptasaccharide glycan. Convergent access to this key α(2,6)-sialylated hexasaccharide was also achieved through a [3+3] glycosylation building upon a Galβ(1,3)[Neu5Acα(2,6)]GalNAc-based trisaccharide donor and a Gb3 acceptor. The synthetic DSGb5 glycan bearing a 6-azidohexyl aglycon at the reducing end could undergo further regioselective functionalization. This approach represents a viable chemoenzymatic method for accessing complex ganglioside glycans and should be useful for the synthesis and biological investigation of DSGb5 derivatives.

中文翻译：

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二唾液酸 Globopentaosylceramide (DSGb5Cer) 聚糖的模块化化学酶法合成。

报道了从恶性肾细胞癌组织中分离出的主要神经节苷脂二唾液酸 globopentaosylceramide (DSGb5 Cer) 的寡糖部分的全合成。合成策略依赖于 Gb5 五糖骨架内部 GalNAc 单元的化学 α(2,6)-唾液酸化，提供 Neu5Acα(2,6)GalNAc 连接的六糖，适用于酶促 α(2,3)-末端 Gal 残基的唾液酸化以构建七糖聚糖。通过基于 Galβ(1,3)[Neu5Acα(2,6)]GalNAc 三糖供体和 Gb3 的 [3+3] 糖基化，也实现了对这一关键 α(2,6)-唾液酸化六糖的收敛访问受体。在还原端带有 6-叠氮己基苷元的合成 DSGb5 聚糖可以进行进一步的区域选择性功能化。