Uronic acids amides

Infrared spectra of glycosaminoglycans in D20 and DC1 were used165 for quantitative evaluation of the uronic acid and acetamido groups in this class of polysaccharide. The results showed that i.r. spectroscopy of compounds in D20 solution provides a simple, quantitative basis for examination of ras(COJ) and amide I bands in heparin and chondroitin 4-sulfate. In DC1, analysis was based on p(C02H) and amide I bands which were well resolved. The apparent acid-dissociation constants of the studied polysaccharides were estimated from the absorbance of p(C02) or p(C02H) bands, or both, at different pH (pD) values. 

Oxidation of methyl 3,4-isopropylidene-2-desoxy-a-D-galactoside with potassium permanganate in the presence of potassium hydroxide afforded methyl 3,4-isopropylidene-2-desoxy-a-D-galacturonoside (LXXXIV) as its potassium salt. This could readily be converted into methyl 2-desoxy-a-D-galacturonoside (LXXXV) and both LXXXIV and LXXXV afforded crystalline esters and amides.230 The uronic acid derivative could be reduced by lithium aluminum hydride in ethereal solution to give methyl 3,4-isopropylidene-2-desoxy-a-D-galactoside.230 Although 2-des-... 

Reactions between D-glucuronic acid, its amide, or 6,3-lactone with various aromatic and aliphatic amines, carbamates, and their derivatives, have often been used for the preparation of (D-glucosyl-amine)uronic acid derivatives of interest as potential drug metabolites or chemotherapeutic agents however, very little evidence is available... 

A (D-glucosylamine)uronic acid derivative has been identified331 as the metabolite of carbamazepine (5//-dibenz[fe,/]azepine-5-carbox-amide, an anti-epileptic agent) by means of permethylation, g.l.c., and mass spectometry. Analytical data for the conjugate (identified in the bile of the isolated, perfused, rat liver) indicated that the carboxamide nitrogen atom is linked to C-l of the sugar moiety. 

Oligomerization of a 7-amino-2,6-anhydro-7-deoxy-heptonic acid results in mimetics of (1 6)-linked sugars with a three-atom instead of a two-atom linker. The sulfated tetramer 24 (O Scheme 7) turned out to exhibit /x-molar activity in the protection of MT2 cells from HIV infection [33], and was also shown to provide heparanase inhibitory activity [34]. With different location of the amide bond, a still benzyl protected /3(1 6)-linked octamer of glucosyl-uronic acid-methyl amine (Gum [35]) 25 was synthesized [36]. 

Humic acids of marine and estuarine sediments are characterized by major amounts of paraffinic structures that previous studies have shown to be highly branched and to contain significant quantities of carboxyl/amide and alcohol/ether carbon. Some humic acids, namely those from well preserved sapropelic marine sediments show significant quantities of carbohydrate-like structures incorporated. This, no doubt, is a reflection of the solubility characteristics of polysaccharides which may have some carboxyl functionalities (uronic acid groups). 

Dichroic Behavior of Carboxyl and Amide Chromophores in Polysaccharide It is evident that the configurational differences of the uronic acid moiety are well reflected in the dichroic behavior of the polymer, and the carboxyl chromophore thus plays a significant role in the chiroptical properties of the molecules. Certain facts regarding carboxyl chromophores are apparent from this study a) monomeric CD properties are well reflected in the Cotton effect of the polymer b) similarities in A0 values (Table 11) between monomers and polymers containing similar uronic acids indicate the additivity of monomer contributions to polymer CD c) iduronic acid shows considerably larger CD than glucuronic acid, which may have some origin in the observed difference in the NMR behavior (29) of methyl a-D-idopyranosiduronic acid from uronic acid with normal C-1 conformation. This has been interpreted in terms of either an equilibrium between the C-1 and 1-C chair forms or adoption of a hybrid skew boat structure. 

Scheme 21 Illustrates the rearrangement of a phenylglyclne amide derivative of gluconic acid and its application to the preparation of an acyclic unsaturated sugar derivative. Likewise the 8-enose derivative (6I) was obtained from the corresponding uronic acid chloride.The same authors similarly produced hexadiene and derived Dlels-Alder adducts from D-gluconlc acid. ...

Uronic acids of the pentose series have been prepared by the oxidative degradation of amides. Mucic acid monoamide can be converted by the action of hydrogen peroxide and iron salts or by hypobromite to the corresponding lyxuronic acid 63), The acids were isolated as the phenylosa-zone-phenylhydrazides, or as the tetraacetates of the amide. 

The condensation of hexuronic acid derivatives with hexosaminides to give amide-linked disaccharides is referred to in Chapter D-Galacturonic acid has been identified as a component of Pneumococcus type 25 capsular polysaccharide," and 2-O-methyl-D-glucuronic acid has been isolated for the first time in Nature from an extracellular polysaccharide of a species (Porphyridium cruentum) of red alga. The acidic sugar component in Klebsiella type 37 capsular polysaccharide has been identified as 4-0-[(5)-l-carboxyethyl]-D-glucuronic acid. Antibiotic substances and nucleosides that contain uronic acid components are referred to in Chapters 20 and 21, respectively. 

By use of pyrrolidine carbohydrate mimetics and a 6-aminoglucose or glucuronic add building block it was demonstrated that isomeric disaccharide mimetics can be prepared by formation of amide- and inverse amide-linked analogs such as 71 and 72 [59]. SPH 73 and several analogs with different uronic acid moieties... 

---