Synthetic Investigation Toward Rebaudioside R And Rebaudioside S

With easy available monosaccharides as well as steviol as starting materials,the first total synthesis of rebaudioside R and Rebaudioside S were accomplished.Trisaccharide sugar chain in the C13-OH of rebaudioside R was formed via linear and convergent strategies.During the linear synthetic study,the effect of protecting groups(PGs)at vicinal hydroxy group on the reactivity of OH acceptors was illustrated.Trisaccharide Yu donors and nitrile solvent effect were used to forge the key ? configuration glucosidic bond in the C13-OH via a convergent strategy,securing the overall synthetic efficiency.Through the modular strategy,the total synthesis of rebaudioside S and its analogues were achieved,at the same time the originally proposed structure was also revised.the effect of the internal glycosidic linkage configuration on the glycosylation stereoselectivity of disaccharide donors was disclosed during the systematic study of the glcosylation between C2-branched disaccharide Yu donors concerned and C13-OH of steviol.