Abstract
Chapter 1: Synthesis of □(2→9) Oligosialic Acids In the first part of this chapter, we accomplished new phosphite-based donors for efficient and highly □-selective synthesis of oligosialic acids (up to pentasialoside) using iterative sialylation. Although the □-selectivity decreased with increasing size of the donor, pure pentasialic acid was obtained on the 10 mg scale. We believe that these phosphite donors will have applications in the development of polysialic acid based vaccines. In the second part, we focussed on the large-scale synthesis of per-O-acetylated saccharides using LiClO4 as a catalyst and a stoichiometric amount of acetic anhydride under solvent free conditions. The peracetylated saccharides smoothly underwent bromination and thioglycosidation in the one-pot synthesis manner to yield synthetically valuable building blocks. Chapter 2: Synthesis of Glycosidases Inhibitors In the first part of this chapter, we described that deoxy-azasugars 150, 154 and pyrrolizidines 153 could be prepared from synthons 3 and 4, respectively. This method provides a structural diversity for the synthesis of many stereoisomers of azasugars, suitable for further studies of their glycosidase inhibitions. . In the second part, we explored a straightforward and convenient method for the synthesis of biologically interesting C-butenyl linked disaccharides using Grubbs’ ruthenium benzylidene as catalyst for olefin cross-metathesis reactions.