致病细菌表面三个含有D-甘露庚糖的复杂寡糖抗原的合成研究

D-manno-Heptose-containing complex oligosaccharide antigens are widely found in the capsular polysaccharides and lipopolysaccharides of pathogenic bacteria. They are usually considered as the major virulence factors of a variety of pathogenic bacteria, thus possessing great potential to be developed into carbohydrate-based synthetic vaccine candidates and diagnostic tools. However, synthesis of orthogonally-protected D-manno-heptose building blocks and beta-stereoselective glycosylation of D-manno-heptose building blocks with alcohols are still quite challenging. In this project, we will develop an efficient approach for the de novo synthesis of orthogonally-protected D-glycero-D-manno-heptose building blocks, enabling the first synthesis of trisaccharide antigen 1 of Helicobacter pylori strains D2, D4 and D5. Moreover, an efficient approach for the de novo synthesis of orthogonally-protected 6-deoxy-D-manno-heptose building blocks will be developed. Glycosylation of 6-deoxy-D-manno-heptose building blocks with various coupling partners will be explored for the assembly of alpha- and beta-6-deoxy-D-manno-heptose residues as well as the alpha-phosphodiester linkage. Synthesis of tetrasaccharide antigen 2 of Burkholderia pseudomallei strain 97 and trisaccharide antigen 3 of Campylobacter jejuni strain RM1221 will be efficiently completed, respectively. These synthetic oligosaccharide antigens can be bound to carrier proteins and array surfaces via the reducing end pentyl amine linker for exploration of their potential applications as carbohydrate-based synthetic vaccines against gastroenteritis, gastric cancer, and melioidosis.

含有D-甘露庚糖的复杂寡糖抗原广泛存在于致病细菌表面的荚膜多糖和脂多糖中。它们被认为是众多致病细菌的重要致病因子，有很大潜力被开发成糖类合成疫苗和医疗诊断工具。然而，正交保护的D-甘露庚糖砌块的合成及其beta-立体选择性糖苷化反应仍然非常具有挑战性。本项目将发展正交保护的D-甘油-D-甘露庚糖砌块的高效从头合成方法，完成幽门螺旋杆菌D2、D4和D5菌株表面的三糖抗原1的首次合成。并且，开发正交保护的6-脱氧-D-甘露庚糖砌块的高效从头合成方法，探索其alpha-和beta-立体选择性糖苷化反应方法以及alpha-构型磷酸二酯键的制备方法，实现类鼻疽杆菌97菌株表面的四糖抗原2和空肠弯曲菌RM1221菌株表面的三糖抗原3的高效合成。这些合成的寡糖抗原的还原端都安装有一个末端为氨基的五碳连接臂，可被连接到载体蛋白和芯片表面，进一步探索其作为糖类合成疫苗来预防肠胃炎、胃癌和类鼻疽等疾病的潜力。

许多致病菌表面含有不同类型的D-甘露庚糖抗原，它们被认为是这些致病菌的重要致病因子，从而成为开发针对这些致病菌的糖类疫苗的重要靶标。然而，结构复杂的D-甘露庚糖砌块的获取及其立体选择性糖苷化反应仍然是一项挑战性的任务。本项目发展了D-甘油-D-甘露庚糖砌块的从头合成方法，完成了幽门螺旋杆菌表面含有D-甘油-D-甘露庚糖的三糖1 的全合成和免疫活性评价，为开发幽门螺旋杆菌糖类疫苗打下了坚实的基础。接着，发展了6-脱氧-D-甘露庚糖砌块的从头合成方法，实现了促进剂辅助的6-脱氧-D-甘露庚糖砌块的β-立体选择性的糖苷化反应，完成了类鼻疽杆菌97菌株表面含有6-脱氧-D-甘露庚糖的四糖2 及其片断的合成，为研制B级生物武器类鼻疽杆菌和鼻疽杆菌的糖类疫苗提供了技术支撑。然后，实现了同一分子中6-脱氧-D-甘露庚糖砌块的α-和β-立体选择性糖苷化反应以及α-构型磷酸二酯键的制备，领先完成了空肠弯曲菌RM1221表面含有6-脱氧-D-甘露庚糖的三糖3的合成，为进一步开发空肠弯曲菌糖类疫苗打下了基础。最后，建立了不同类型D-甘露庚糖的高效合成平台，实现了副溶血性弧菌O2脂多糖中独特的α-L,D-Hep-(1→3)-α-D,D-Hep-(1→5)-α-Kdo核心三糖的立体选择性合成，为其它致病菌表面含有D-甘露庚糖的复杂寡糖抗原的合成提供了新的策略。

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