Pseudoaldobiouronic acids

K3. Kuenzle, C. C., Bilirubin conjugates of human bile. The excretion of bilirubin as the acyl glycosides of aldobiouronic acid, pseudoaldobiouronic acid and hex-uronosylhexuronic acid, with a branched-chain hexuronic acid as one of the components of the hexuronosylhexuronide. Biochem. J. 119, 411-435 (1970). 

The mass spectra of permethylated pseudoaldobiouronic acids demonstrate that the principles for fragmentation just described are valid for this class of compound. Mass spectra have been recorded for 21 permethylated trisaccharides. The nature of the monosaccharide residues... 

The reaction of 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide with methyl (methyl 2-0-methyl-a-D-galactopyranosid)uronate in the presence of silver carbonate has yielded the crystalline pseudoaldobiouronic acid derivatives methyl [methyl 2-0-methyl-3-0- and 4-0-(2,3,4,6-tetra-0-acetyl-)3-D-gluco-pyranosyl)-a-D-galactopyranosid]uronate. Deacetylation of the compounds followed by Kuhn methylation afforded mainly crystalline, fully methylated products. 

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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