Polyglycosiduronic acids

Polyfructosans. See Fructans. Polyglycosiduronic acids. See Glyco-siduronic acids, poly-. Polysaccharides. See also, Carbohydrates,... 

The occurrence in many polyglycosiduronic acids of relatively resistant linkages, usually those between uronic acid residues and adjacent residues, has resulted in the isolation of several aldobiouronic acids on graded hydrolysis of acidic polysaccharides. The isolation of such aldobiouronic acids, and subsequent conversion to their fully methylated derivatives, has become a standard procedure in structural studies on polyglycosiduronic acids, especially those of plant gums and mucilages.1 In other cases, partially methylated aldobiouronic acids have been isolated from the hydrolyzates of methylated polysaccharides. The sources and methods of isolation of the methyl ethers of aldobiouronic acids so far examined are given in Table I. Some properties of derivatives are recorded in Table Y. 

Although, in both cases, the polyglycosiduronic acids are more stable than their esters, they are not completely stable to alkaline solutions. For example, 43% of the glycosidic bonds in 4-0-(i8-D-glucopyranosyluronic acid)-D-glucaric acid are cleaved in 20 min. with 0.1 A sodium hydroxide at 20°. Some instability would be expected because of the well-known formation of a,(3-unsaturated acids from /3-hydroxy acids. 3-0-Substituted... 

The seaweed polyglycosiduronic acid alginic acid, whichj is composed of D-mannuronic and L-guluronic acid residues, when treated with a partially purified preparation of a cell-free extract of an adapted pseudomonad, is initially depolymerized to a series of oligosaccharides each of which contains a 4-deoxy-L-er2/terminal position, and then to the h-erythro isomer of the ulosonic acid (107), which is the product formed from both of the constituent residues. 

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