Disaccharides, from aldobiouronic acids

Like the parent compounds, the methyl ethers of aldobiouronic acids are resistant to acid hydrolysis, and it is difficult to carry out hydrolysis without some decomposition of the product. This difficulty has recently been overcome by reduction of the uronic acid residue with lithium aluminum hydride66-67 the resulting disaccharide then undergoes hydrolysis without difficulty. The first reduction of the uronic acid residue of a methylated aldobiouronic acid methyl ester was accomplished by Levene, Meyer and Kuna,69 who reduced the methylated aldobiouronic acid from gum arabic with hydrogen in the presence of copper chromite catalyst under the conditions previously used701 for reducing the acety-... 

Reducing disaccharide. Widespread as the aldobiouronic acid unit of plant polysaccharides, particularly of plant mucilages and gums. e.g. isol. from or detected in partial acid hydrolysates of Linum usitatissimum (flax), Ulmus fulya (slippery ehn), Plantago seed, Hibiscus esculentus (okra), Salvia aegytica mucilages and others. Amorph. [a]o +50.8 (H2O). [a] +96.1 (c, 0.4 in H2O). [a]g +105.5 (c, 1.06 in H2O). 

Several bilirubin conjugates have been isolated from human hepatic bile as the phenylazo derivatives. The major bilirubin conjugates are excreted, not as was formerly thought in the form of glucuronides, but as the acyl glycosides of three aldobiouronic acids, one hexurono l-hexuronic acid, and one pseudoaldobiouronic acid. The conjugation of human metabolites with acidic disaccharides of the above types has not been reported previously. 

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