Synthesis of branched D-xylofuranan by selective, ring-opening polymerization of silylated 1,5-anhydro-beta-D-xylofuranose, and its conversion into a blood anticoagulant.

Selective ring-opening polymerization and copolymerization of 1,5-anhydro-D-xylofuranose derivatives were studied. Stereoregular (1----5)-alpha-D-xylofuranan was synthesized from a new monomer, 1,5-anhydro-2,3-di-O-(tert-butyldimethylsilyl)-beta-D-xylofuranose , with phosphorus pentafluoride and antimony pentachloride as catalysts in dichloromethane. Copolymerization of 3 with 1,5-anhydro-2,3-di-O-benzyl-beta-D-xylofuranose, and desilylation of the copolymer with tetrabutylammonium fluoride gave a partially benzylated stereoregular (1----5)-alpha-D-xylofuranan which was glycosylated with 3,4,6-tri-O-acetyl-beta-D-mannose 1,2-(methyl orthoacetate) to give a branched polymer. Deprotection of the benzylated polymer having D-mannosyl branches with sodium in liquid NH3 gave (1----5)-alpha-D-xylofuranans having 2- or 3-O-alpha-D-mannopyranosyl branches. Sulfation of the free D-xylofuranans was achieved with piperidine sulfate. The sulfated D-xylofuranan having branches showed high blood-anticoagulant activity.