Streptococcus pneumonia (SPn) is a Gram-positive bacterium which causes life threatening diseases. The bacteria protect themselves against non-specific host defence by an external polysaccharide (PS) capsule which bears a repeating unit, α-D-Galp(1->3)-α-D-Glcp(1->3)-α-L-Rhap(1->3)-D-Rib (SPn 6A). A closer look at the structure reveals the presence of α-linked galactose and glucose residues. The synthesis of these 1,2-cis glycosidic linkages are considered challenging particularly in the context of a one-pot oligosaccharide synthesis. We have synthesized the aforesaid tetrasaccharide (SPn 6A) based on both stepwise and sequential one-pot glycosylation reactions using easily accessible common building blocks; eventually similar overall yields were obtained in both cases.
肺炎链球菌(
SPn)是一种革兰氏阳性细菌,能引起威胁生命的疾病。这些细菌通过一种外部
多糖(PS)胶囊来保护自己,免受宿主非特异性防御,这种胶囊带有重复单元,α-D-Galp(1->3)-α-D-Glcp(1->3)-α-L-Rhap(1->3)-D-Rib(
SPn 6A)。仔细观察其结构可以发现α连接的半
乳糖和
葡萄糖残基的存在。这些1,2-
cis糖苷键的合成被认为是具有挑战性的,特别是在一锅
寡糖合成的情况下。我们已经合成了上述的四糖(
SPn 6A),基于逐步和顺序的一锅糖基化反应,使用易于获取的常见构建模块;最终在这两种情况下获得了相似的总收率。