Multiple and Regioselective Introduction of Protected Sulfates into Carbohydrates Using Sulfuryl Imidazolium Salts
作者:Ahmed Y. Desoky、Scott D. Taylor
DOI:10.1021/jo901882f
日期:2009.12.18
Selective incorporation of trichloroethyl (TCE)-protected sulfates into monosaccharides was examined using reagent 2. In general, sulfation of 4,6-O-benzylidene acetals of galactosides and glucosides (2-OH versus 3-OH sulfations) proceeded in good to excellent yield and selectivity. Sulfation occurred predominantly at the 2-OH in 4,6-O-benzylidene acetals of α-glucosides and at the 3-OH in 4,6-O-benzylidene
Chemoselective glycosidation strategy based on glycosyl donors and acceptors carrying phosphorus-containing leaving groups: a convergent synthesis of ganglioside GM3
A convergent synthesis of gangliosideGM3 has been achieved by capitalizing on three different phosphorus-containing leaving groups, in which the key features involve a chemo- and regioselective α-glycosidation of sialyl phosphite with partially benzylated galactosyl tetramethylphosphorodiamidate by the aid of trifluoromethanesulfonic acid and a traditionally uncommon coupling of an α-sialyl-(2→3)-galactosyl
glycosylation of a sialylated disaccharide with a glucosaminyl donor. This synthetic route enabled the synthesis of the as‐described disialylated structure. A more‐convergent route based on the glycosylation of two sialylated disaccharides was also established to scale up the synthesis. Protection of the amide groups in the sialic acid residues significantly increased the yield of the glycosylation reaction