Glucuronic acid, from glucose

Figure 11.5 Formation of methylated saccharinic acids from glucose and cellulose, and methylated deoxyglucaric acid from glucuronic acid [66,681...

The substance glucuronic acid can be considered to be glucose with carbon 6 oxidized to the carboxylic acid level. Glucuronic acid /3-glycosides are the metabolic fate of a number of obnoxious compounds found in plants. Draw the structure of glucuronic acid. From its name can you guess where it was first found ... 

The chemical preparation of D-glucuronic acid from D-glucose was formerly tedious and unsatisfactory it has been simplified recently by protection of the aldehyde group through glycosidation, followed by oxidation of the hydroxyl group at C6 and hydrolysis.26 The reactions of D-glucuronic acid are discussed elsewhere.6 7... 

Fig. 2-24. Preparation of D-glucuronic acid from D-glucose. The primary hydroxyl group at C-6 is selectively oxidized after protection of the anomeric center (see Fig. 2-17). The most useful reagent for oxidation is oxygen in the presence of platinum metal but potassium permanganate and dinitrogen tetroxide can also be applied.

Polysaccharides have been isolated from the crude enzyme complex, papain, and two of them contain the same sugar residues, D-glucuronic acid, D-glucose, D-galactose, L-arabinose, and L-rhamnose but in the ratios 4 1 12 10 4 and 13 1 40 26 12. ° The polysaccharides seriously affected the aggrega-... 

Potentiometric titration and other physical data indicated that the native polysaccharide possesses an ordered secondary structure that is stabilized by nonionic interactions, which outweigh the repulsion between adjacent carboxy-groups. An acidic heteropolysaccharide from Xanthomonas SI 9 is composed of residues of D-glucuronic acid, D-glucose, o-galactose, D-mannose, and acetate. Although methylation analysis showed that this polysaccharide possesses many structural features similar to those of other Xanthomonas polysaccharides, it is unusual in that D-mannosyl and D-galactosyl residues occur in the structure. 

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