500212-94-2Relevant academic research and scientific papers
Syntheses of α- and β-glycosyl donors with a disaccharide β-D-Gal-(1→3)-D-GalNAc backbone
Cheshev,Kononov,Tsvetkov,Shashkov,Nifantiev
, p. 419 - 429 (2007/10/03)
The synthesis of thioglycoside glycosyl donors with a disaccharide β-D-Gal-(1 → 3)-D-GalNAc backbone was studied using the glycosylation of a series of suitably protected 3-monohydroxy- and 3,4-dihydroxyderivatives of phenyl 2-azido-2-deoxy-1-thio-α- and 1-thio-β -D-galactopyranosides by galactosyl bromide, fluoride, and trichloroacetimidate. In the reaction with the monohydroxylated glycosyl acceptor, the process of intermolecular transfer of thiophenyl group from the glycosyl acceptor onto the cation formed from the molecule of glycosyl donor dominated. When glycosylating 3,4-diol under the same conditions, the product of the thiophenyl group transfer dominated or the undesired (1 → 4), rather than (1 → 3)-linked, disaccharide product formed. The aglycon transfer was excluded when 4-nitrophenylthio group was substituted for phenylthio group in the galactosyl acceptor molecule. This led to the target disaccharide, 4-nitrophenyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β -D-galactopyranosyl)-1-thio-β-D-galactopyranoside, in 57% yield. This disaccharide product bears nonparticipating azido group in position 2 of galactosamine and can hence be used to form α-glycoside bond. Azido group and the aglycon nitro group were simultaneously reduced in this product and then trichloroacetylated, which led to the β-glycosyl donor, 4-trichloroacetamidophenyl 4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl) -1-thio-2-trichloroace-tamido-β-D-galactopyranoside, in 62% yield. The resulting glycosyl donor was used in the synthesis of tetrasaccharide asialo-GM1.
