RING-OPENING POLYMERIZATION OF 1,4-ANHYDRO-ALPHA-D-GLUCOPYRANOSE DERIVATIVES HAVING ACYL-GROUPS AND SYNTHESIS OF (1-]5)-BETA-D-GLUCOFURANAN

The influence of initiator, solvent, monomer concentration, and temperature on the ring-opening polymerization of 1,4-anhydro-2,3-di-O-benzyl-6-O-pivaloyl-alpha-D-glucopyranose (1) and 1,4-anhydro-3,6-di-O-benzyl-2-O-pivaloyl-alpha-D-glucopyranose (2) was investigated. Polymerization of 1 gave nonstereoregular polymers consisting of mainly (1-->5)-alpha-glucofuranosidic units with an [alpha](D) value of ca.+84 degrees. Polymerization of 2 with phosphorus pentafluoride catalyst produced new stereoregular polysaccharide derivatives, 3,6-di-O-benzyl-2-O-pivaloyl-(1-->5)-beta-D-glucofuranans, with an [alpha](D) value of ca.-60 degrees. Substituted polymers were characterized by H-1- and C-13-NMR spectroscopy, polarimetry, and gel permeation chromatography. Debenzylation and depivaloylation of the substituted polymers afforded unsubstituted (1-->5)-beta-glucofuranan. The electronic effect on the ring-opening polymerization and the mechanism of the ring-opening polymerization are discussed. This is the first paper to describe the preparation of (1-->5)-beta-glucofuranan with an [alpha](D) value of ca.-204 degrees.