Two novel synthetic methods for 1,4-anhydro-α-d-xylopyranose derivatives

Two novel methods for the syntheses of 1,4-anhydro-3-O-benzyl-2-O-pivaloyl- (1) and 2-O-acetyl-1,4-anhydro-3-O-benzyl-α-d-xylopyranose (2), starting materials for synthesizing stereoregular β-(1→5)-xylofuranan by ring-opening polymerization are reported. Both synthetic routes start from d-xylopyranose, involve nine reaction steps, and give approximately 30–35% overall yields. The key reaction in the novel synthetic routes is the intramolecular nucleophilic attack of C-1 oxyanion on the C-5 position of 3-O-benzyl-5-O-(p-toluenesulfonyl)-α-d-xylofuranose (10), resulting in 1,5-acetal bond formation in high yield. The present synthetic routes enable us to prepare 1,4-anhydro-α-d-xylopyranose derivatives having different substituents at the 2-O- and the 3-O-positions.