Study On The High Efficient Method Of ?-sialyation

Sialic acids are a family of acidic 9 carbon sugars compound,and are often found?-sialoside linked to other sugars at the termini of glycoconjugated chains in biological systems which are involved in a wide range of biological processes.With picolinyl group as the C-1 located participating group,which was installed and cleaved efficiently,and C5-N₃ as the versatile precursor for C₅-NH₂,a novel 1-Pic-5-N₃ thiosialyl donor was designed and synthesized,based on which a new sialylation protocol was established.In comparison to the conventional sialylation protocols,the new protocol exhibited the obvious advantages of excellent?-stereoselectivity,broad substrate scope,flexibility in sialoside derivative synthesis,and,in particularly,applicability in synthesis of complex and bioactive N-glycan antennae when combined with the MPEP glycosylation protocol.Mechanically,the excellent?-stereoselectivity of the novel sialylation protocol was attributed to the dramatically electron-withdrawing effect of the protonated Pic group;meanwhile the high reactivity as well as excellent?-stereoselectivity of sialyl donor with electron-withdrawing protecting group on C-1 was disclosed for the first time.