Uronic adds

Pyruvate ketals add to the anionic nature of the exopolysaccharide and are usually present in stoichiometric ratios with the carbohydrate component Pyruvate is normally attached to the neutral hexoses but may also be attached to uronic adds. In the absence of uronic acids, pyruvate alone contributes to the anionic nature of the exopolysaccharide. 

True. Uronic adds contribute to the anionic nature of exopolysaccharides. 

Bergamaschi, B.A., J.S. Walters, and J.I. Hedges. 1999. Distribution of uronic adds and dimethyl sugars in sedimentary particles in two coastal marine environments. Geochimica et Cosmochimica Acta 63 413-425. 

Constituents of Various Mucilages that Contain Uronic Add Residues... 

Octosyl Acids. Three octosyl uronic add nucleosides are produced by S. cacaoi sub sp asoensis. 

Tissue PG GAG Core protein No. total uronic add) (%w/w) References ... 

Uronic adds may be identified and determined by reduction to the alditols and conversion thereof into alditol acetates. An acid commonly encountered in glycuronans is 4-O-methyl-n-glucuronic acid, but, on an ECNSS-M column, 4-O-methylgludtol and galactitol acetates are not well separated however, they are cleanly resolved on butanediol succinate. In some instances, the degree of separation achieved with ECNSS-M may be markedly influenced by the nature of the solid support used. Thus, this liquid phase on Chromosorb not add-washed may give longer retention-times, but improved resolution. ... 

Modification of the primary, 6"-hydroxyl group of kanamycin A has been extensively studied by Umezawa and coworkers. Tetra-N-(benzyl-oxycarbonyl)kanamycin A was selectively p-toluenesulfonylated or naphthalenesulfonylated at 0-6" and the product converted into the corresponding chloro (216) and iodo derivative. - Catal) c hydrogenation of the iodo derivative gave " 6"-deoxykanamycin A (217). These 6"-halogeno and 6"-deoxy derivatives have an activity similar to that of the parent antibiotic. Kanamycin-6"-uronic add (218), its esters, and amide, and kanamycin 6"-phosphate (Ref. 245) (219) and 4",6"-0-benzylidene-kanamycin were prepared and found to have decreased antibacterial activity. 

Ester 155 was converted by the Tebbe method to the methylene analogue (92%) which underwent Claisen rearrangement to give the C-linked uronic add derivative 156 (56%). ... 

The sugars appear as chromatogram zones of various colors (yellow, pale pink, ted to blue) on an almost colorless background [1-3, 6, 7]. Uronic adds acquire a bdge> to violet-pink coloration [2, 4, 6]. 

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