糖苷化反应是糖合成化学的核心。离去基团的性质是影响糖苷化效率的关键因素之一。该项目旨在研究硫代炔丙基黄原酸酯（SPXO）作为多功能离去基团在糖苷化中的应用。SPXO不仅能在异头位，而且更为独特的是它也能在C-2位作为离去基团用于构建包括2-脱氧糖-贝塔-糖苷键在内的不同类型糖苷键。Velutinoside A是一结构新颖但难以分离获取的孕甾糖苷，其全合成和生物功能的研究还未见报道。基于发展的糖苷化方法，该项目将通过构建4个2-脱氧-L-鼠李糖-贝塔-糖苷键和1个L-岩藻糖-贝塔-糖苷键，完成velutinoside A的全合成并对其进行抗炎活性研究。牛樟芝半乳甘露聚糖具有重要的免疫调节活性，是潜在的免疫和疫苗佐剂。该项目将采用SPXO糖苷化反应和水相中形成酰胺键的新策略合成系列牛樟芝寡糖糖簇分子并研究其生物活性，该策略有望为制备组成均一、结构明确且与天然多糖更接近的模拟物开辟新途径。

Glycosylations are the cornerstone of chemical synthesis of glycoconjugates. The nature of leaving group at the anomeric center is among the crucial factors having influence on the glycosylations. This proposal aims to investigating the applications of S-propargyl xanthates as versatile leaving groups in glycosylations. In this proposal it will be demonstrated that not only S-propargyl xanthates can act as leaving groups at the anomeric position to construct various glycosidic bonds, but also they have a salient feature, namely, being the leaving groups at C-2 position of sugar rings to mediate formation of challenging beta-glycosidic linkages of 2-deoxysugars. Total synthesis of velutinoside A with the unique structure, but difficult to isolate from natural sources will be achieved in this proposal through constructing four challenging 2-deoxy-beta-L-rhamnosidic linkages and one 2-deoxy-beta-L-fucosidic linkage relying on gold-catalyzed S-propargyl xanthate glycosylations. Anti-inflammation effects of velutinoside A will also be studied in this project. It should be noted that there is no reports on total synthesis of velutinoside A and its biological relevance to date. On the other hand, since galactomannan, isolated from the native Taiwan fungi Antrodia cinnamomea, exhibits significant immunomodulatory activities and is a promising adjuvant in immunotherapy and vaccination, this project, built on S-propargyl xanthate glycosylations and formation of amide bonds in aqueous phase, will focus on synthesis of a panel of glycoclusters of Antrodia cinnamomea oligosaccharides and their bioactivities and structure-activity-relationship of immunomodulatory effects. The synthetic strategy for glycoclusters offers opportunities for constructing homogenous and structurally well-defined glycomimetics resembling the natural polysaccharides.of velutinoside A and its biological relevance to date. On the other hand, since galactomannan, isolated from the native Taiwan fungi Antrodia cinnamomea, exhibits significant immunomodulatory activities and is a promising adjuvant in immunotherapy and vaccination, this project, built on the well-known cluster glycoside effects and S-propargyl xanthate glycosylations, will focus on synthesis of a panel of glycodendrimers of Antrodia cinnamomea oligosaccharides and their bioactivities and structure-activity-relationship of immunomodulatory effects, setting a solid foundation for developing novel carbohydrate-based medicines.