Sugars, acylation detection

The hexuronosylhexuronide presumably is the acyl 4-0-(3-C-hydroxy-methylribofuranosyluronic acid)-)8-x)-glucosiduronic acid, with the term acyl standing for the phenylazo derivative of bilirubin. The 3-C-hydroxy-methylriburonic acid, isolated as one of the components of the hexuronosylhexuronide, is the first natural branched-chain hexuronic acid to be recognized, and the first branched-chain sugar ever detected in humans. 

Occurrence. D-Lyxose (7), a rare sugar, has been detected in glycolipids from Mycobacterium phlei. The pentose is substituted by an acyl group at position 2 and in some instances, at both positions 2 and 4. It is difficult to distinguish d-lyxose from D-arabinose, and thus, a wider distribution in Mycobaterium should be... 

N. hesperis was the only Nicotiana species where the major sugar ester acyl groups were normal chain acids. Low levels of unsaturated acyl groups were detected in the sugar ester hydrolysates of several of the species. The unsaturated acyl group, 2-methyl-2-butenoyl, was a major component in the sugar ester isolates from N hesperis. 

TLC on silica gel G has been useful particularly in the organic synthesis of amino sugars for the characterization of derivatives which are not readily detected on paper. It has found application in the synthesis of 4-acetamido-4-deoxy-D- reofuranose [41], 2,6-diamino-2, 6-dideoxy-D-mannose dihydrochloride [42], 2,3-epimino-hexopyranosides [43], 2-amino-2,6-dideoxy-D-galactose [44], the l-O-acyl-2-acylamido-... 

The RBP molecule is a single polypeptide chain of about 180-185 amino acid residues containing three intramolecular disulfide bonds (as cystine residues) (Rask et al., 1981). No fatty acid or fatty acyl chains were detected in purified RBP (Kanai et al., 1968). Analyses for carbohydrate showed that RBP was free of neutral sugar and hexosamine (Peterson, 1971) and had a maximum of 0.9 mol of hexose per mol of protein (Raz et al., 1970). It is likely that RBP contains no bound lipid (other than retinol) and no carbohydrate. 

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