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)-alpha-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-alpha-D-xylopyranose (A3ASX). First, A3ASX was polymerized by BF3.OEt2 catalyst at -20 to -40 degrees C to give 3-azido-2-O-tert-butyldimethylsilyl-(1-->5)-alpha-D-xylofuranan (3AzSXF) with (M) over bar(n) of 11.1 x 10(4)-17.8 x 10(4) and [alpha](D) of +200-212 degrees. A polymer prepared by SbCl5 catalyst had a mixed structure consisting of 1,5-alpha- and 1,5-beta-xylofuranosidic units. 3AzSXF was reduced with NaBH4 in a THF- ethanol mixture to afford 3-amino-2-O-tert-butyldimethylsilyl-3-deoxy-(1-->5)-alpha-D-xylofuranan (3AmSXF). After 3AmSXF was acetylated at its amino groups to produce a 3-acetamidoxylofuranan derivative (3AAdSXF), desilylation of 3AAdSXF gave 3AAdXF with (M) over bar(n) of 7.8 x 10(3) and [alpha](D) of +212 degrees. The structure analysis was performed using C-13 and H-1 NMR spectroscopies, IR spectroscopy, and optical rotation measurements.