505. The catalytic oxidation of European larch ε-galactan

Abstract

A s+inaLl and Nicolson. 2503 505. The Catalytic Oxidation of European Larch E-Galactan?By G. 0. ASPINALL and A. NICOLSON.Catalytic oxidation of larch E-galactan results in selective oxidation of primary alcoholic groups with the formation of carboxylic acids. Graded hydrolysis of the oxidised polysaccharide gives two aldobiouronic acids, (6-~-galactose p-D-galactopyranosid)uronic and (6-n-galactose L-arabinofuranosid)uronic acid. The structural significance of these and other results is discussed.

Chemical Modification of Polysaccharides

“…In many respects, this is an attractive method, since molecular oxygen is used as the oxidising agent, water is the sole by-product, and in principle, heterogeneous catalysts can be easily recovered and reused. However, this method has a significant disadvantage when it comes to the oxidation of polysaccharides: as the catalyst is heterogeneous, the degree of oxidation (DS ox ) can be quite low [122]. It is generally true that homogeneous catalysts will give better results for the modification of insoluble polymeric substrates.…”

“…It is generally true that homogeneous catalysts will give better results for the modification of insoluble polymeric substrates. Nevertheless, inulin with a DP of ca 30 could be oxidised to the uronic acid level at the primary positions (C-6) with a DS ox of ca 0.20 under such conditions [123], and C-6 oxidation of a galactan over platinum to the uronic acid level with a DS ox of ca 0.15 has also been achieved [121, 122, 124]. Purification was carried out by precipitation followed by membrane filtration.…”

Modication of Heterocyclic Amino Acids: Histidine and Tryptophan

“…In many respects, this is an attractive method, since molecular oxygen is used as the oxidising agent, water is the sole byproduct, and in principle, heterogeneous catalysts can be easily recovered and reused. However, this method has a significant disadvantage when it comes to the oxidation of polysaccharides: as the catalyst is heterogeneous, the degree of oxidation (DS ox ) can be quite low [122]. It is generally true that homogeneous catalysts will give better results for the modification of insoluble polymeric substrates.…”

Controlled Oxidation of Dextran for Evolution of Polyether Segment Bearing Pendant Carboxyl Groups for Corrosion Inhibition Applications

“…A significant increase in the selectivity was accomplished by Besemer et al using 2,2,6,6-tetramethyl-1-piperidinyloxy as a mediator and hypochlorite/bromide as an ultimate oxidant under basic conditions (pH [10][11]. 12 This reaction was exploited for determination of a small amount of primary alcohol groups as a defect in dextran, a (1!6)--D-glucan.…”