Synthesis of 3-Acetamido-3-deoxy-(1→5)-α- d -xylofuranan by Ring-Opening Polymerization of a 1,4-Anhydro-3-azido-α- d -xylopyranose Derivative

A stereoregular 3-acetamido-3-deoxy-(1→5)-α- d -xylofuranan (3AAdXF) was synthesized by the synthetic route starting from selective ring-opening polymerization of 1,4-anhydro-3-azido-2- O - tert -butyldimethylsilyl-3-deoxy-α- d -xylopyranose (A3ASX). First, A3ASX was polymerized by BF 3 ·OEt 2 catalyst at −20 to −40 °C to give 3-azido-2- O - tert -butyldimethylsilyl-(1→5)-α- d -xylofuranan (3AzSXF) with M̄ n of 11.1 × 10 4 −17.8 × 10 4 and [α] D of +200−212°. A polymer prepared by SbCl 5 catalyst had a mixed structure consisting of 1,5-α- and 1,5-β-xylofuranosidic units. 3AzSXF was reduced with NaBH 4 in a THF−ethanol mixture to afford 3-amino-2- O - tert -butyldimethylsilyl-3-deoxy-(1→5)-α- d -xylofuranan (3AmSXF). After 3AmSXF was acetylated at its amino groups to produce a 3-acetamidoxylofuranan derivative (3AAdSXF), desilylation of 3AAdSXF gave 3AAdXF with M̄ n of 7.8 × 10 3 and [α] D of +212°. The structure analysis was performed using 13 C and 1 H NMR spectroscopies, IR spectroscopy, and optical rotation measurements.