Polysaccharide hydrolyzates, isolation

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. 

Mild, acid hydrolysis of European-larch arabinogalactan results in the formation of 3-0-/3-L-arabinopyranosyl-L-arabinose (XXXIX). 26 Although this disaccharide has been isolated as an acid-reversion product from L-arab-inose,131 it is accompanied under these conditions by two other arabinose-containing disaccharides, neither of which was detected in the larch polysaccharide hydrolyzate. Since hydrolysis of methylated -galactan gave approximately equimolar proportions of 2,3,4-tri-O-methyl-L-arabinose and 2,5-di-O-methyl-n-arabinose, traces of 2,3,5-tri-O-methyl-L-arabinose, and no mono-O-methyl-L-arabinose, it is clear that the L-arabinose units must arise from an arabinogalactan rather than from an arabinan, and that the majority of these must be present in 3-0-/3-L-arabinopyranosyl-L-arabino-furanose side-chains (XLV) linked, in some way as yet unknown, to the framework of D-galactose units (XLI). 

HemiceUulose is a mixture of amorphous branched-chain polysaccharides consisting of a few hundred sugar residues. They are easily hydrolyzed to monomeric sugars and uronic and acetic acids. Many different hemiceUuloses have been isolated from wood. 

Bacillus krzemieniewski(f). This soil bacillus forms thick, gelatinous capsules on carbohydrate media and yields a polysaccharide which on hydrolysis is stated to produce L-mannose.660 This claim is based upon the melting point of the isolated mannose phenylhydrazone and upon the rotation of the hydrolyzed reaction mixture. It requires further confirmation. 

Problem 22.36 Cellobiose, isolated from the polysaccharide cellulose, has the same chemistry as maltose except that it is hydrolyzed by emulsin. Give the structure of this disaccharide. ... 

GlcA-(l— 4)-l-Fuc was isolated from partial, acid hydrolyzates of soybean polysaccharide,134 the pectin of leaves of Tussilago,135 and tragacanthic acid,136 and a-L-Fuc-(l— 2)-D-Xyl was obtained from soybean polysaccharide.25... 

Structural Analysis of a Polysaccharide A polysaccharide of unknown structure was isolated, subjected to exhaustive methylation, and hydrolyzed. Analysis of the products revealed three methylated sugars in the ratio 20 1 1. The sugars were 2,3,4-tri-O-methyl-D-glucose 2,4-di-O-methyl-D-glucose and 2,3,4,6-tetra-O-methyl-D-glucose. What is the structure of the polysaccharide ... 

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