CONSTITUTION OF A SYNTHETIC GLUCAN: III. PERIODATE OXIDATION

Abstract

A synthetic glucan known to contain D-glucofuranose and D-glucopyranose units was subjected to a Smith periodate degradation. After mild acid hydrolysis any aldehydic compounds were oxidized with bromine and the neutral fragments separated from the acidic by ion exchange resins. The acidic portion, after lactonization and reduction, gave glycerol and a series of oligosaccharides. The neutral portion was resolved into glycerol, erythritol, and a series of seven fractions containing glycosides with degrees of polymerization up to eight. Each fraction which was homogeneous by paper chromatography contained at least two components. Some of these individual components were separated as their trimethylsilyl derivatives by vapor phase chromatography and the following glycosides were identified: 1-O-(α-D-glucopyranosyl)-glycerol, 1-O-(β-D-glucopyranosyl)-glycerol, 2-O-(D-xylofuranosyl)-D-erythritol, 2-O-(α-D-glucopyranosyl)-D-erythritol, 2-O-(β-D-glucopyranosyl)-D-erythritol, 1-O-(D-glucopyranosyl)-erythritol. These results demonstrate for the first time the separation of Smith degradation products by vapor phase chromatography. The presence in the polysaccharide of α and β linkages and the existence of D-glucofuranose residues are confirmed. The highly branched nature of the polymer is shown by the fact that four successive periodate oxidations and mild hydrolyses were necessary to oxidize all the hexose units.