Studies On The Synthesis Of Bioactive Flavonoid 5-O-Glycosides And The New Glycosylation Method

1.Highly stereoselective synthesis of flavonoid 5-O-glycosides via gold(I)-catalyzedcamellianins B is a structurally typical representatives of flavonoid 5-Oglycosides,as ingredients of an antihyperglycemic fraction consists in Camellia sinensis and Cephalotaxus sinensis.wherein the challenging apigenin 5-Oglycosidic linkages were fashioned with glycosyl ortho-alkynylbenzoates as donors under the catalysis of Au(I).The first total synthesis of the proposed camellianin B was achieved via three different routes.In the first route,a linear tactic was adopted.The other two routes,a convergent strategy was adopted.All three routes yielded the same products,verifying the correctness of the synthetic compound.The resultant peracetylated authentic target molecules was then subjected to thorough 1D and 2D NMR analyses,which eventually led to the final structure revision of camellianins B and A.2.New Glycosylation Donors for Highly Efficient Construction of Glycosidic LinkagesOligosacchride and glycoconjugates play critical roles in an array of biological processes.Glycosylation to construct glycosidic linkages is the central theme in the synthesis of oligosacchride and glycoconjugates.A novel alkyne activation based glycosylation protocol,ortho-(para-methoxyphenylethynyl)phenyl(MPEP)glycoside protocol,was established,which features broad substrate scopes both for donors and acceptors as well as mild glycosylation conditions.A wide variety of these donors are shelf stable and easily prepared.The combination of the MPEP glycosylation method with the latent-active strategy led to the highly efficient synthesis of Streptococcus Pneumoniae trisaccharides glycosidic bond.The present method also fit into the orthogonal one-pot glycosylation strategy,as exemplified by the syntheses of tetrasaccharides via three successive glycosylation steps with glycosyl TCI,ABz,and MPEP as donors with 68% and 65% overall yields and within 7 hours.