Aryl 4-thioxylobioside and 1,4-dithioxylobiosides as effectors of the enzymic activity for fungal d-xylanases

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-beta-D-glucopyranose with 1,6-anhydro-3,4-dideoxy-2-O-p-toluenesulfonyl-beta-D-erythro-hex-3-enopyranose gave 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl-(1-->4)-1,6-anhydro-2,3-dideoxy-4-thio-beta-D-erythro-hex-2-enopyranose in 86% yield. Its 1,6-anhydride bond was cleaved with methanol to give a mixture of methyl glycosides (alpha/beta approximately 5:1), from which the alpha 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.

Synthesis of 2- and 4-nitrophenyl beta-glycosides of beta-(1-->4)- D-xylo-oligosaccharides of dp 2-4

2- and 4-Nitrophenyl beta-D-xylopyranosides (4 and 5) were transformed, via dibutyltin oxidemediated acylation, into the corresponding 2,3-di-O-benzoyl derivatives 11 and 15. Xylobiose and xylotriose were easily isolated by charcoal column chromatography from a commercially available material and converted into the di- and trisaccharide methyl 1-thio-beta-glycosides 36 and 37. The 2-and 4-nitrophenyl beta-glycosides of the beta-(1-->4)-D-xylo-oligosaccharides of dp 2-4 were synthesized by N-iodosuccinimide-silver triflate-promoted condensation using 11 and 15 as the glycosyl acceptors and ethyl 1-thio-beta-D-xylopyranoside triacetate 16, 36, and 37 as the glycosyl donors. Also described are an improved preparation of 4 and 5, and the synthesis of 1-naphthyl beta-D-xylopyranoside, as well as an alternative approach to the 2- and 4-nitrophenyl beta-xylobiosides.