Synthesis of methyl 4-thio-β-cellobioside. A reinvestigation

The best yield for the synthesis of the title compound was obtained by nucleophilic displacement of the 4-O-triflyl group in methyl tri-O-benzyl-4-O-triflyl-β-d-galactopyranoside by 2,3,4,6-tetra-O-acetyl-1-S-acetyl-1-thio-β-d-glucopyranose in HMPA in the presence of diethylamine. Under these conditions, the formation of unsaturated side products was decreased.