Glucuronic acid,

A number of derivatives of D-glucuronic acid have been made by Goebel and Babers with a view to their use in the synthesis of aldobionic acids. With the same object Owen, Peat and Jones prepared both pyranose and furanose derivatives of D-glucurone. 

On acetylation, D-glucurone gives a mixture of a- and 3-triacetyl-D-glucurones (V) which on treatment with acetyl chloride and hydrogen 

By the action of cold acid methyl alcohol on n-glucuronolactone, Owen, Peat and Jones obtained a crystalline compound of empirical formula CtHmOo which was shown to have the structure X, viz., methyl (S-D-glucofunironoside 3,6-lactone, by the following series of reactions. 

Methylation of X with silver oxide and methyl iodide gave the lactone of methyl 2,5-dimethyl-3-D-glucofururonoside (XIII) which was characterized by its conversion to the crystalline amide (XIV). Further methylation of XIII, j8 form, with methyl sulfate and sodium hydroxide gave methyl 2,3,5-trimethyl-/S-D-glucofururonoside (XVI) from which by hydrolysis of the glycosidic methyl group and subsequent oxidation with bromine, there was obtained 2,3,5-trimethyl-D-glucosaccharolactone (XVII) characterized by the formation of its crystalline methyl ester. 

Certain anomalous optical and reducing properties of the compound X find a ready explanation in the fact that it possesses two five-membered rings in the molecule, for Smith has shown that such dicyclic systems in the carbohydrate group readily enolize in the presence of alkali. Treatment of X with hot acidic methyl alcohol brings about a ring change from furanose to pyranose and there is produced the methyl ester of methyl n-glucopyruronoside (XV) identified by methylation and conversion to the amide (XII). 

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Glycoproteins or mucoproieins. Compounds of proteins with carbohydrates. All glycoproteins contain a hexosamine and usually sulphate, ethanoate and glucuronic acid. The carbohydrate-protein linkages are, in some cases covalent and in others of the salt type. Aqueous solutions of glycoproteins are extremely viscous. 

They are found in a great variety of plants and are strong fish poisons. On hydrolysis they yield a variety of sugars, frequently several molecules to each aglucone. Glucose, galactose, arabinose are the more common pentoses, methylpentoses and glucuronic acid are also obtained. 

Uronic acids are biosynthetic intermediates m various metabolic processes ascorbic acid (vitamin C) for example is biosynthesized by way of glucuronic acid Many metabolic waste products are excreted m the urine as their glucuronate salts... 

A.- ng deduction. This is an irreversible reaction which is a foremost determinant of the secretion rate of cortisol (double bonds and C-3 carbonyl). Catalyzed predominantiy by cortisone P-reductase and 3a-hydroxysteroid dehydrogenases, SP sterols result, although 5a sterols are more prevalent in the case of other glucocorticoids. Urocortisol and urocortisone result from the metabohsm of cortisol and cortisone, respectively. Compounds can be complexed to glucuronic acid at this point. 

Glucuronidation. Complexation of the steroid to glucuronic acid, most predominantiy via the C-3 hydroxyl, leads to a considerable portion of the excreted metabohtes of ah. glucocorticoids. In infants, sulfurylation (formation of a sulfate ester) is also predominant (16). 

Gum ghatti is the calcium and magnesium salt of a complex polysaccharide which contains L-arabinose, D-galactose, D-mannose, and D-xylose and D-glucuronic acid (48) and has a molecular weight of approximately 12,000. On dispersion in water, gum ghatti forms viscous solutions of viscosity intermediate between those of gum arabic and gum karaya. These dispersions have emulsification and adhesive properties equivalent to or superior to those described for gum arabic. 

Uronic acids are monosaccharides in which the terminal primary alcohol group is oxidized to a carboxyhc acid functional group, eg, D-glucuronic acid [6556-12-3] (11). 

P -D-xylan with 3-hnked a-L-arabiaose branches (1 4)-P -D-xylan with 2-Unked 4-0-methyl-a-D-glucuronic acid and arabiaose branches... 

Glc = glucose GlcA = glucuronic acid GulA = guluronic acid Man = mannose ManA = mannuronic acid Rha = rhamnose Xyl = xylose Fuc = fucose. Chemical structures and properties are available (19). 

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