Efficient Stereoselective Synthesis Of2-Deoxy Glycosides And Glycoconjugates

The thesis includes two parts:1. Research on glycosylation of2-deoxy glycosides.2. Studies on the synthesis of2-deoxy oligosaccharides and glycoconjugates.1.2-Deoxy sugars are common structural units in many natural products possessing important biological properties; however, stereoselective synthesis of2-deoxy-a glycosides can be difficult to achieve due to the lack of directing group at the C-2position and acid lability of the resulting2-deoxy glycosides. Although many direct methods have been developed for the synthesis of2-deoxy-a-glycosides, high catalyst loading and low temperature are often required. We have developed a direct method using2-deoxy glycosyl acetates as glycosyl donors under the catalysis of TMSOTf for the synthesis of2-deoxy-a-glycosides. The current approach proceeds in mild conditions (0℃) with high yield (81-99%), and its application is widespread to a variety of alcohols.2. Biological properties of many natural antibiotics and antitumor medicines are associated with carbohydrate moieties. In order to synthesize their2-deoxy analogues and probing their biological properties, glycosyl acceptors from sugars including glucose, galactose, mannose, and rhamnose to amino acids derivatives including serine, threonine, and tyrosine were successfully synthesized. These acceptors were successfully applied in the synthesis of a-2-deoxy oligosaccharides and a-2-deoxy glycoconjugates with good to excellent a-selectivity (>2:1) in moderate to high yield (60～99%) by direct glycosylation. These results show that a practical method using2-deoxy glycosyl acetates as donors for synthesis of2-deoxyglycosides in direct glycosylation can be employed in the total synthesis of natural products and their analogues.