The coupling reaction of N-acetyl-5-N,4-O-oxazolidinone protected p-toluenethiosialoside 1, with four kinds of benzyl or benzoyl protected methyl galactoside diols was deeply studied, which showed α-selectivity with α/β＝1.6～2.0 and afforded the corresponding sialylation products in high yields (72%～89%). Based on these results, a methyl 2,3,6,2’,6’-penta-O-benzyl-β-lactoside 17 was prepared from lactose with 7 steps in a 19% total yield. Sialylation of compound 17 with donor 1 successfully produced the methyl glycoside ganglioside GM3 trisaccharide derivative in a 68% yield and α/β＝1.6∶1.

Key words: sialic acid, ganglioside GM3, glycosylation, oxazolidinone