Glucopyranosyluronic acid

Structure of xanthan has been determined by chemical degradation and methylation analysis (335,336) it is composed of repeating units consisting of a main chain of D-glucopyranosyl residues with trisaccharide side chains made up of D-mannopyranosyl and D-glucopyranosyluronic acid residues. 

Fig. 9. Partial structural formulas and shorthand notations for principal hemiceUuloses found in wood, where the sugar units ate noted as P-D-xylopyranose (Xylp), 4-Omethyl-a-D-glucopyranosyluronic acid (GlupU), a-L-arabinofuranose (Araf), P-D-glucopyranose (Glup), P-D-mannopyranose (Manp), and P-D-galactopyranose (Galp) for (a) arabino-4-O-methylglucuronoxylan from softwood, (b) 0-acetyl-galactoglucomannan from softwood, and...

Xanthan. Xanthan, known commercially as xanthan gum [11138-66-2], has a main chain of (1 — 4)-linked P-D-glucopyranosyl units therefore, the chemical stmeture of the main chain is identical to the stmeture of cellulose [9004-34-6]. However, in xanthan, every other P-D-glucopyranosyl unit in the main chain is substituted on 0-3 with a trisaccharide unit. The trisaccharide side chain consists of (reading from the terminal, nonreducing end in towards the main chain) a -D-mannopyranosyl unit linked (1 — 4) to a P-D-glucopyranosyluronic acid unit linked (1 — 2) to a... 

The pyruvic acid may also be linked to vicinal positions. When linked to 0-3 and 0-4 of a D-galactopyranosyl residue (40), the dioxolane ring becomes cw-fused. In the limited number of known examples, the absolute configuration at the acetalic carbon atom is (S), as in 40. There are some examples of tra -fused dioxolane rings, and these are more sensitive to hydrolysis with acid than the others. Thus, pyruvic acid is acetalically linked to 0-3 and 0-4 of an a-L-rhamnopyranosyl residue in the Klebsiella type 72 capsular polysaccharide, to 0-2 and 0-3 of an a-D-galactopyranosyl residue in the Streptococcus pneumoniae type 4 capsular polysaccharide, and to 0-2 and 0-3 of a S-D-glucopyranosyluronic acid residue in the Klebsiella K1 capsular polysaccharide. " In the extracellular polysaccharide from... 

C17H28015 3 H20 0-(4-0-Methyl-a-D-glucopyranosyluronic acid)-(l — 2)-0-/ -d-xylopyranosyl-(l— 4)-a-D-xylopyranose, trihydrate GURXPX10 31 354... 

The sole component of the uridine diphosphate uronic acid fraction from animal tissues,10,124,139 Chlorella,4 red algae,83 and some bacteria118,119 is uridine 5 -(a-D-glucopyranosyluronic acid pyrophosphate) (32), whereas a similar preparation from Pneumococcus140 contains only the a-D-galactopyranosyluronic acid derivative. Both esters have been shown to occur in extracts of mung bean.141,142... 

UDP-D-glucuronic acid by the uridine 5 -(a-D-glucopyranosyluronic acid pyrophosphate) cyclase of L. minor. 

Ci7H28015 3H20 0-(4-0-Methyl-ot-D-glucopyranosyluronic acid)-(1 — 2)-0-/3-D-xyIopyranosyl-( 1 — 4)-a-D-xylo-pyranose trihydrate,34 m.p. 179°C... 

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