Ring-opening polymerization and copolymerization of a new benzylated 1,6-anhydro-3-azido-3-deoxy-beta-D-allopyranose and synthesis of amino-polysaccharides with 1,6-alpha-allopyranosidic structure

Ring-opening polymerization of a new anhydro-hexose monomer having an azido group, 1,6-anhydro-3-azido-2,4-di-O-benzyl-3-deoxy-beta-D-allopyranose (A3ABA), was carried out with Lewis acid catalysts to give a stereoregular (1-->6)-alpha-D-allopyranan derivative having the azido group at the C3 position. The number-average molecular weights and specific rotations were 5.0 x 10(3) to 24.0 x 10(3) and +71 degrees to +79 degrees, respectively. Reduction of the azido groups into amino groups by lithium aluminium hydride and subsequent debenzylation of the benzyl groups into hydroxyl groups by sodium in liquid ammonia gave 3-amino-3-deoxy-(1-->6)-alpha-D-allopyranan in good yield. In addition, copolymerization of A3ABA with 1,6-anhydro-2,3,4-tri-O-benzyl-beta-D-glucopyranose (LGTBE) in the various feeds was carried out to afford the corresponding copolymers. The monomer reactivity ratios were calculated with the Kelen-Tudos method to be r(A3ABA) = 0.66 and r(LGTBE) = 1.67. After reduction of azido groups and deprotection of benzyl groups of the copolymers, new hetero-polysaccharides having different contents of glucopyranose and 3-amino-allopyranose units were obtained.