Synthesis and cationic ring-opening polymerization of 1, 4-anhydro-2, 3-di-O-(p-azidobenzyl)-α-D-ribopyranose

New highly stereoregular 2, 3-di-O-(p-azidobenzyl)-(1 --> 5)-alpha-D-ribofuranan was synthesized by selective ring-opening polymerization of 1, 4-anhydro-2, 3-di-O-(p-azidobenzyl)-alpha-D-ribopyranose (ADABR) using phosphorus pentafluoride or tin tetrachloride as catalyst at low temperature in dichloromethane. The monomer was obtained by the reaction of p-bromomethyl-phenyleneazide with 1, 4-anhydro-alpha-D-ribose in DMF. The structure of poly(ADABR) was identified by specific rotation and C-13-NMR spectroscopy. Acid chloride-AgCl4 complex catalyst such as CH2 = C(CH3)C+OClO4- used in the polymerization resulted in polymers with mixed structures, i.e. (1 --> 5)-alpha-D-ribofuranosidic and (1 --> 4)-beta-D-ribopyranosidic units. However, with C6H5C+OClO4- as catalyst, pure (1 --> 5)-alpha-D-ribofuranan was obtained. The effects of catalyst, polymerization temperature and time on polymer stereoregularity were examined, and the mechanism of the ring-opening polymerization was discussed.