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Hexuronic acids

Note The dipping solution, which can also be used as a spray solution, can be employed with silica gel, kieselguhr, cellulose, RP, NH2 and CN phases. Sugars (exceptions include, for example, fructose, melezitose and raffinose) yield brilliantly colored zones on an almost colorless background when the spray solution is employed. Aldohexoses appear brown, aldopentoses bright red and hexuronic acids orange in color [3]. The detection limit differs for different substances it ranges from 10 ng (pyridoxal) over 100 ng (cinnamaldehyde) up to 2 pg (citral). [Pg.158]

Structural Identification of Isomeric O-Trimethylsilyl Derivatives of Some Hexuronic Acids, J. F. Kennedy, S. M. Robertson, and M. Stacey, Carbohydr. Res., 57 (1977) 205-214. [Pg.41]

Heterocyclics 252, 260, 299,416 n-Hexadecanol esters 63 Hexaporphyrin 102 Hexitols 426 Hexobarbital 254,255 Hexoses 161,202 Hexuronic acid 158 Histamine 294,296, 355 Homogentisic acid 166,167 Horizontal chamber 127 Hotplates 93 ff -, temperature distribution 95 Hydrazines 269,284 Hydrazone formation 71 ff -with 2,4-dinitrophenylhydrazine 71, 72, 274... [Pg.236]

Epimerization at C-5 of hexuronic acids is a reaction that proceeds both on the polymer and on the sugar nucleotide level. In addition to the three pairs of parent acids, namely, the u-glucolL-ido-, D manno/L-gulo-, and D-ga-lacto/L-altro-he uron c acids, the 2-amino-2-deoxy acids belonging to the last two and the 2,3-diamino-2,3-dideoxy acids belonging to the middle pair have been found. [Pg.318]

It will be appropriate to consider first the building units of the carbohydrate residues and it will be immediately apparent that D-mannose and D-galactose with N-acetyl-amino sugars and hexuronic acids play a predominant role. It is proposed, therefore, to discuss briefly some of the more important discoveries connected with the two latter groups and with the carbohydrate sulfates. [Pg.183]

Biosyntheses of hexuronic acids and L-ascorbic acid in plants and animals are closely related. Hexuronic acids, L-ascorbic acid, and L-tartaric acid (a possible precursor of dihydroxyfumaric acid) commonly occur together in plants. If a rat is given chloretone (an antispasmodic), both L-ascorbic acid and D-glucuronic acid are excreted in increased quantity.244 Unlike humans, rats can synthesize their own vitamin C, and are therefore independent of outside sources. Here, D-glucose and D-galactose can be utilized, but not D-mannose. [Pg.240]

D-Glucofuranosylamine)uronic acids attained biological significance after nucleoside antibiotics containing hexuronic acid residues were isolated from natural sources examples are gougerotin and blasticidin S. [Pg.200]

Hexuronic acids are decarboxylated in the presence of refluxing, aqueous acid to form 5, reductic acid (2,3-dihydroxy-2-cyclopenten-l-one 47) and very small amounts of 48 (5-formyl-2-furoic acid). The yields of these products decrease when dilute acid solutions are used. Most of this work was performed with hydrochloric acid the use of phosphoric acid was not nearly so effective. For instance, D-galacturonic acid quantitatively lost CO2 within 4 h with 3.5 A/ HCl, whereas only 12 mole% of the CO2 was recovered after 4 h with 1.2 M H3PO4. The yields of CO2 from several hexuronic acids (including polygalacturonic acid) were comparatively determined. The acidic decarboxylation of hexuronic acids is bi-molecular and dependent on both the hexuronic acid and hydrochloric acid concentrations. Prior labeling work had established that C-6 of the hexuronic acid is the source of the CO2. [Pg.288]

The three acid-derived components of the hexuronic acids, namely, 5, 47, and 48, are essentially end products in the reaction. This is quite surprising, as 48 required only decarboxylation to form 2-furaldehyde. However, the rate of decarboxylation of the furoic acid was <2% of that of D-galacturonic acid under similar conditions. Furthermore, no trace of pentoses was noted in any of the reaction mixtures, which eliminates previous suggestions of their role in the mechanism of 2-furaldehyde for-... [Pg.288]

K3. Kuenzle, C. C., Bilirubin conjugates of human bile. The excretion of bilirubin as the acyl glycosides of aldobiouronic acid, pseudoaldobiouronic acid and hex-uronosylhexuronic acid, with a branched-chain hexuronic acid as one of the components of the hexuronosylhexuronide. Biochem. J. 119, 411-435 (1970). [Pg.284]

Scheme 32 ALkylidene derivatives of hexuronic acid 6,3-lactone... Scheme 32 ALkylidene derivatives of hexuronic acid 6,3-lactone...

See other pages where Hexuronic acids is mentioned: [Pg.11]    [Pg.5]    [Pg.40]    [Pg.487]    [Pg.255]    [Pg.187]    [Pg.192]    [Pg.193]    [Pg.198]    [Pg.201]    [Pg.185]    [Pg.186]    [Pg.237]    [Pg.238]    [Pg.241]    [Pg.242]    [Pg.461]    [Pg.462]    [Pg.351]    [Pg.432]    [Pg.293]    [Pg.31]    [Pg.285]    [Pg.55]    [Pg.257]    [Pg.289]    [Pg.290]    [Pg.319]    [Pg.320]    [Pg.241]   
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