Monosaccharide uronic acids from

Chromatographic separation of free nucleotides from various sources usually gives the glycosyl esters of uridine 5 -pyrophosphate in three fractions, containing fhe derivatives of neutral monosaccharides, uronic acids, and 2-acetamido-2-deoxyglycoses, respectively. 

Oxidation of primary alcohols. This selective oxidation system allows the preparation of uronic acids from monosaccharide derivatives. 

Rha, Ara and Gal are the neutral sugar components from all the fractions. Xyl is not present in Fla and is significantly present in the hemicellulose fractions, indicating that this monosaccharide is component of hemicellulosic polymers. Chemical composition of the water fractions were determined (Table V). High protein contents and the presence of O-acetyl-groups were observed in four aqueous fractions. Neutral sugar and uronic acid composition points to inclusion of these polymers in the class of pectic polysaccharides. 

Dermatan sulfate, also termed chondroitin sulfate B, a related glycosaminoglycan constituent of connective tissue, was known to be composed of galactosamine and a uronic acid, originally believed to be glucuronic acid but then claimed to be iduronic acid based largely on color reactions and paper chromatography. However, the d or L-enantiomer status of the latter monosaccharide was not clear. Jeanloz and Stoffyn unequivocally characterized the monosaccharide as L-iduronic acid by consecutive desulfation, reduction, and hydrolysis of the polysaccharide, followed by isolation of the crystalline 2,3,4-tri-0-acetyl-l,6-anhydro-/ -L-idopyranose, which was shown to be identical to an authentic specimen synthesized from 1,2-0-isopropylidene-/ -L-idofuranose.34... 

There are three possible classes of sugar acids which may be produced by the oxidation of monosaccharides (Figure 9.11). The aldonic acids are produced from aldoses when the aldehyde group at carbon 1 is oxidised to a carboxylic acid. If, however, the aldehyde group remains intact and only a primary alcohol group (usually at carbon 6 in the case of hexoses) is oxidised then a uronic acid is formed. Both aldonic and uronic acids occur in nature as intermediates in... 

Methanolysis of standard uronic acids has been studied by Inoue and Miyawaki in regard to the depolymerization of chondroitin sulfate and dermatan sulfate. These workers found the glucosiduronic linkage to ga-lactosamine to be rather resistant to methanolysis, but that it is more efficiently cleaved after deamination of the amino galactoside, with its conversion into 2,5-anhydrotalose. For iduronic, glucuronic, and man-nuronic acids released from a polymer, it was found that the peaks monitored for these acids, relative to an internal standard, increase during the first 8 h of methanolysis (M hydrogen chloride, 100°) and remain constant for up to 20 h of methanolysis. This indicated that 8 h is required for complete methanolysis, and that the monosaccharides liberated are stable to the conditions of methanolysis. 

The ion-exchange separation usually affords individual fractions of structurally related glycosyl esters of nucleoside pyrophosphates, containing the same nucleotide residue, but differing in the structure of the glycosyl groups. Separation of the esters of N-acetylhexos-amines, uronic acids, and neutral monosaccharides from one another is also usually achieved. 

The consumption of effective alkali in a kraft cook corresponds to about 150 kilogram sodium hydroxide per ton of wood. As a result of the alkaline degradation of polysaccharides, about 1.6 equivalents of acids are formed for every monosaccharide unit peeled from the chain. Of the charged alkali, 60-70% is required for the neutralization of these hydroxy acids, while the rest is consumed to neutralize uronic and acetic acids (about 10% of alkali) and degradation products of lignin (25-30% of alkali). 

Uronic acids are important components in many naturally occurring polysaccharides. By chemical or enz)matic degradation of these polysaccharides, smaller uronic acid units ranging from monosaccharides to smaller oligosaccharides can be prepared. In this connection, reduction of the carboxyl group can serve both synthetic and analytical purposes. 

Monosaccharide units derived from oxidised or reduced sugars are important components of polysaccharides. The most important deoxy sugars are L-rhamnose (6-deoxy-L-mannose) and L-fucose (6-deoxy-L-galactose). Uronic acids are sugars in which the 6 position has been formally oxidised to a carboxylic acid, and form the major basis for anionic polysaccharides. Important... 

The particular value of acid hydrolysis is that, used in conjunction with paper chromatography, much evidence may be obtained from very small amounts of compound. As the identification of monosaccharides by paper chromatography is well established, the use of this technique in conjunction with total, acid hydrolysis provides a ready means for identifying, both qualitatively and quantitatively, the monosaccharide components of an oligosaccharide. Acid stability of different glycosidic links differs, and total hydrolysis may require from one to four hours at 100° in N acid even more vigorous conditions may be required when amino sugar or uronic acid residues are present. Very rapid hydrolysis in dilute acid,... 

The noncellulosic fraction of SB hull polysaccharides consists mainly of xylose and mannose. The acidic polysaccharides that can be extracted from SB hulls in sequential extractions steps (acidic polysaccharides 1-V) are all very similar in structure with interior chains made up of D-galacturonic acid and L-rhamnopyranose residues. These interior acidic chains are associated with side chains consisting of neutral sugars, including L-arabinose and chains of 1 4 linked P-D-galactopyranose residues. In addition, 2-O-P-D-gal-D-xyl and 2-O-a-L-fuc-D-xyl residues also may be present (Aspinall et al., 1966). Although the acidic polysaccharide fractions I—V are similar structurally, upon hydrolysis they may yield different monosaccharide concentrations. For example, acidic polysaccharide III contains 76% uronic acids, whereas fractions IV and V contained approximately 45% uronic acids. Hydrolysis of the acidic polysac-... 

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