Ring-Opening Polymerization of a Benzylated 1,6-Anhydro-β-D-talopyranose and Synthesis of a New Polysaccharide, (1-6)-α-D-Talopyranan

1,6-Anhydro-2,3,4-tri-O-benzyl-β-d-talopyranose (1) was synthesized and polymerized to compare its polymerizability with that of other benzylated 1,6-anhydrohexopyranoses reported previously. In methylene chloride at −60 °C, phosphorus pentafluoride as the initiator gave stereoregular polymers (2) with number-average molecular weights (Mn) of 9500−19 600. The polymerizability was analyzed based on the configuration of the hydroxyl groups and conformational change of the pyranose ring during polymerization. The monomer reactivity ratios resulting from copolymerization with 1,6-anhydro-2,3,4-tri-O-benzyl-β-d-glucopyranose (4) were also compared. The present monomer 1 required a large amount of the initiator for polymerization. 31P NMR results of polymerization suggested that considerable amounts of the initiator coordinated with not only the oxygen of the 1,6-anhydro ring of the monomer but also those of the polymer. This additional coordination of the initiator with the polymer oxygens is expected to decre...