Study On The Stereoselective Synthesis Of C-Glycosides Of 2-Deoxy-2-Amino Sugars

C-Glycosides exhibit significantly increased stability towards hydrolytic enzymes in vivo than corresponding O/N-glycosides,hence holding great potential as therapeutic agents and biological probes.At the same time,2-deoxy-2-amino sugars(2DAS)are essential components of oligosaccharides of both N-and O-glycopeptides,which play vital roles in a diversity of biological processes.Consequently,new methods for constructing C-glycosides of 2DAS are valuable in biological chemistry and medicinal chemistry.However,existing synthetic methods often require the use of stoichiometric toxic tin reagents and are generally α-selective.In this thesis,we have demonstrated for the first time that the imidate radical can be added to glycals effectively to yield glycosyl radicals and developed a general,radical approach for the synthesis of alkyl C-glycosides of 2-deoxy-2-amino sugars(2DAS).Notable features of this method include:(i)It does not use any toxic tin reagents;(ii)it is a rare example of 1,2-trans stereoselective,radical synthesis of Cglycosides;(iii)it is the first application of aryl alkenes as substrates for alkyl-Cglycosides(of 2DAS).As the reaction conditions are mild and the dihydrooxazole group is easy to remove,the method is suitable for the late-stage functionalization of drug molecules(e.g.estrone).The control experiments proved the involvement of glycosyl radicals,and the DFT calculations indicate that shape of glycosyl radicals directed the 1,2-trans stereoselectivity.Overall,this thesis’ s results provide a new means for the stereoselective synthesis of C-glycosides,which would be beneficial to the development of related biochemical research.