Silver Oxide Catalyzed Rhamnose Hydroxyl Selective Protection Methods, Research And Application

In this thesis, we report a highly regioselective 2-monoacylation in 3-O-benzylatedα-L-rhamnopyranosides in the presence of a stoichiometric amount of silver(I) oxide. This novel method allows for the convenient generation of a variety of differentially functionalized L-rhamnose building blocks in 56-78% yields. Efficent preparations of two branched rhamnose fragments have been accomplished by utilizing this method, which provided opportunity for further total syntheses and bioactivity investigations of the parent glycosides.Gleditsioside-type triterpene saponins exhibit significant cytotoxic activity against human leukemia cells. Empolyment of the monosaccharide synthon, derived from the above method as a critical glycosylating partner, permitted an efficient assembly of a branched tetrasaccharide portion, which might be an essential intermediate for preparation of C-28 side chain of gleditsiosides C and D.Merremoside-type resin glycosides are naturally ocurring glycolipids with novel skeleton. They are composed of macrolide and exocyclic oligosaccharide. But there haven't been any reports so far about the structure-activity relationships of these compounds. In our research, we have developed a facile approach to synthesize a protected exocyclic trisaccharide fragment of merremoside G.