Vaccines against S. pneumoniae, one of the most prevalent bacterial infections causing severe disease, rely on isolated capsular polysaccharide (CPS) that are conjugated to proteins. Such isolates contain a heterogeneous oligosaccharide mixture of different chain lengths and frame shifts. Access to defined synthetic S. pneumoniae CPS structures is desirable. Known syntheses of S. pneumoniae serotype 3 CPS rely on a time-consuming and low-yielding late-stage oxidation step, or use disaccharide building blocks which limits variability. Herein, we report the first iterative automated glycan assembly (AGA) of a conjugation-ready S. pneumoniae serotype 3 CPS trisaccharide. This oligosaccharide was assembled using a novel glucuronic acid building block to circumvent the need for a late-stage oxidation. The introduction of a washing step with the activator prior to each glycosylation cycle greatly increased the yields by neutralizing any residual base from deprotection steps in the synthetic cycle. This process improvement is applicable to AGA of many other oligosaccharides.
针对导致严重疾病的最常见细菌感染之一的肺炎球菌的疫苗依赖于与蛋白质结合的分离的胶囊多糖(CPS)。这种分离物包含不同链长和框移的异质寡糖混合物。获得定义明确的合成肺炎球菌CPS结构是可取的。已知的肺炎球菌3型CPS的合成依赖于耗时且产率低的后期氧化步骤,或者使用二糖建筑块,这限制了变异性。在这里,我们报告了第一个迭代自动糖基组装(AGA)的可结合的肺炎球菌3型CPS三糖的组装。使用一种新型葡萄糖醛酸建筑块组装了这种寡糖,以避免需要后期氧化。在每个糖基化周期之前引入一个活化剂的洗涤步骤大大增加了产量,通过中和合成周期中去保护步骤中的任何残留碱。这个工艺改进适用于许多其他寡糖的AGA。