Regioselective Synthesis of Sugar-chain Unit Involved in Glycoconjugate by Glycosidase

N-乙酰乳糖胺1(Gal beta1-4GlcNAe)是一种具有代表性的二糖，在糖蛋白和糖脂组成的寡糖中具有重要的核心作用。由于作为生物材料的需求日益增长，我们开发了一条由乳糖和N-乙酰氨基葡萄糖(GlcNAc)通过环状芽孢杆菌的β-D-半乳糖苷酶进行糖基化反应合成1-乙酰氨基葡萄糖的实用路线。此外，利用环状芽孢杆菌β-D-半乳糖苷酶的转糖作用，合成了含有2-乙酰氨基-2-脱氧-D-己糖的β-(1-4)连接二糖和三糖。以GlcNAe和GalNAc的衍生物S为受体。酶反应的效率足够高，使我们能够从乳糖中一锅制备β-(1-4)连接的半乳糖基低聚糖。在该酶作用下，D-半乳糖基转移优先发生在GlcNAc和GalNAc羟基构型的C-4位。

N-Acetyllactosamine 1(Gal beta1-4GlcNAe)is known as a representative disaccharide which is itself important as a core component in oligosaccharide moieties of glycoproteins and glycolipids. Owing to the growing need for substantial amount of 1 as a biomaterial, we have developed a practical route for the synthetic of 1 from lactose and Nacetylglucosamine(GlcNAc), utilizing the transglycosylation reaction through beta-D-galactosidase from Bacillus circulans. Furthermore, utilization of the transglycosylation by B. circulans beta-D-galactosidase led to the synthesis of beta-(1-4)linked disaccharides and trisaccharides containing a 2-acetamido-2-deoxy-D-hexose. The derivative s of GlcNAe and GalNAc were used as acceptors for the preparations. The enzyme reaction was efficient enough to allow us to perform the one pot preparation of beta-(1-4)-linked galactosyl-oligosaccharide from lactose. With the enzyme, D-galacosyl transfer occurred preferentially at the C-4 position of GlcNAc and of GalNAc, respectively, of the configuration of the hydroxyl group.