title: Preparation of completely C6-carboxylated curdlan by catalytic oxidation with 4-acetamido-TEMPO.
abstract: Pure (1→3)-β-polyglucuronic acid sodium salt was prepared from curdlan by oxidation with 4-acetamido-TEMPO/NaClO/NaClO₂ in water at pH 4.7 and 35°C. The oxidation conditions, including the reaction time and amounts of reagents added, were optimized for the preparation of (1→3)-β-polyglucuronic acids with high molecular weights. The primary C6 hydroxyl groups of curdlan were completely oxidized to the corresponding C6-carboxylates using a one- or two-step reaction process by controlling the oxidation conditions, thus providing pure (1→3)-β-polyglucuronic acids consisting only of D-glucuronosyl units. Unfortunately, however, the increased amounts of reagents and long reaction time led to significant depolymerization of the curdlan during the oxidation process, and the resulting (1→3)-β-polyglucuronic acids had weight-average degrees of polymerization of 340-360. The (13)C and (1)H NMR chemical shifts of the products were successfully assigned using pure (1→3)-β-polyglucuronic acid.
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Erika
authors.initials: E
authors.lastname: Watanabe
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Tamura
authors.forename: Tsuguyuki
authors.initials: T
authors.lastname: Saito
authors.forename: Naoto
authors.initials: N
authors.lastname: Habu
authors.forename: Akira
authors.initials: A
authors.lastname: Isogai
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D002384:Catalysis; D002712:Chlorides / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D010084:Oxidation-Reduction; D058105:Polymerization; D012973:Sodium Hypochlorite / Q000737:chemistry; D047071:beta-Glucans / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D002712:Chlorides; D003497:Cyclic N-Oxides; D047071:beta-Glucans; C038459:curdlan; D020723:Glucuronic Acid; D012973:Sodium Hypochlorite; C003959:TEMPO; C001599:chlorite
keywords: (1→3)-β-Polyglucuronic acid; 4-Acetamido-TEMPO; Curdlan; Molecular weight; Oxidation