Synthesis of the globotetraose tetrasaccharide and terminal tri- and di-saccharide fragments

Article abstract of DOI:10.1016/0008-6215(94)90010-8

The 2-(trimethylsilyl)ethyl (TMSEt) β-glycosides of globotetraose <β-D-GalNAc-(1 -> 3)-α-D-Gal-(1 -> 4)-β-D-Gal-(1 -> 4)-D-Glc> and the terminal trisaccharide, as well as the methyl α-glycoside 1 of the terminal disaccharide, were synthesised by silver trifluoromethanesulfonate-promoted β-glycosylation of suitably protected galactoside, galabioside, and globotrioside alcohols with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-galactopyranosyl chloride, followed by removal of protecting groups.Removal of the anomeric TMSEt group of the globotetraoside and of the terminal trisaccharide, using trifluoroacetic acid-dichloromethane, gave the corresponding hemiacetal sugars 8 and 3.The TMSEt glycoside of the terminal trisaccharide was converted, via the 1-acetate, into the corresponding isobutyl (4) and 3-butylsulfonyl-2-<(butylsulfonyl)methyl>propyl (5) glycosides and into the TMSEt thioglycoside 6 via the glycosyl bromide.