Synthesis of S-linked glucosaminyl-4-thiohex-2-enopyranosides via allylic SN2′ substitution of a tosylhexenose

Treatment of 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-1-thio-β-d-glucopyranose with 1,6-anhydro-3,4-dideoxy-2-O-p-toluenesulfonyl-β-d-erythro-hex-3-enopyranose gave 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl-(1→4)-1,6-anhydro-2,3-dideoxy-4-thio-β-d-erythro-hex-2-enopyranose in 86% yield. Its 1,6-anhydride bond was cleaved with methanol to give a mixture of methyl glycosides (α/β∼5:1), from which the α anomer was separated by crystallization and converted into its 6-acetate, 6-methanesulfonate, or deacetylated to obtain the corresponding free methyl thiodisaccharide. The structure of the new compounds was confirmed by 1H and 13C NMR spectra.