Sugar Derivatives

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1 Sugar derivatives There are many important compounds that are derived from monosaccharides. They include sugar acids, sugar alcohols, deoxy sugars and amino sugars 1- Sugar acids They are the oxidation products of monosaccharides. According to the site of oxidation sugar acids are classified into: a- Aldonic acids It is produced by oxidation of carbonyl group (C1 in aldoses) to carboxylic group e.g. gluconic acid from glucose. H C O COOH H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH CH2 OH CH2 OH Glucose Gluconic acid b- Uronic acids It is produced by oxidation of the last carbon e.g. glucuronic acid from glucose. H C O H C O H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH CH2 OH COOH Glucose Glucuronic acid 2 Glucunonic acid is important in: - Detoxication reactions - Biosynthesis of mucopolysaccharides - Metabolism of bilirubin - Excretion of steroids. c- Aldaric acid (Saccharic acid) It is a dicarboxylic acid resulting from oxidation of both carbonyl carbon and last carbon e.g. glucaric acid from glucose. H C O COOH H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH CH2 OH COOH Glucose Saccharic acid d- L-Ascorbic acid (vitamin C) It is a water soluble vitamin. It is a 6-carbon sugar acid derived from glonic acid. 2- Sugar alcohols Aldoses and Ketoses may be reduced at the carbonyl carbon to the corresponding sugar alcohols D-Sorbitol from D-glucose D-mannitol from D-mannose D-ribitol from D-ribose Inositol is a cyclic alcohol derived from glucose. OH OH H H H H H H OH OH OH OH 3 It is a member of vitamin B complex that acts as a lipotropic factor preventing accumulation of fats in the liver Also, inositol triphosphate has a role in the mechanism of action of some hormones. 3- Deoxysugars These are monosaccharides with one hydroxyl group (usually at C2) is replaced by hydrogen e.g. 2-deoxyribose which is a constituent of DNA. 4- Amino sugars These are monosaccharides in which the hydroxyl group at C2 is replaced by amino group. Glucosamine and galactosamine are examples of amino sugars. H C O H C O H C OH H C NH2 HO C H HO C H H C OH H C OH H C OH H C OH CH2 OH CH2 OH Glucose Glucosamine Amino sugars are important for biosynthesis of mucopolysaccharides and glycoproteins. Glucosamine which is derived from glucose is a constituent of heparin and hyaluronic acid Galactosamine which is derived from galactose is a constituent of chondriotin sulphate. .

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Redox and Complexation Chemistry of the Crvi/Crv–D-Galacturonic Acid System
Redox and complexation chemistry of the CrVI/CrV–D-galacturonic acid system Juan C. González,a Verónica Daier,a Silvia García,a Bernard A. Goodman,b Ana M. Atria,c Luis F. Sala*a and Sandra Signorella*a a Departamento de Química, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Suipacha 531, 2000, Rosario, Argentina. E-mail: [email protected]; [email protected] b Scottish Crop Research Institute, Invergowrie, Dundee, Scotland, UK DD2 5DA c Facultad de Ciencias Químicas y Farmacéuticas and CIMAT, Universidad de Chile, Casilla 233, Santiago, Chile The oxidation of D-galacturonic acid by CrVI yields the aldaric acid and CrIII as final products when a 30-times or higher excess of the uronic acid over CrVI is used. The redox reaction involves the formation of intermediate CrIV and CrV species, with CrVI and the two intermediate species reacting with galacturonic acid at comparable rates. The rate of disappearance of CrVI, CrIV and CrV depends on pH and [substrate], and the slow reaction step of the CrVI to CrIII conversion depends on the reaction conditions. The EPR spectra show that five-coordinate oxo–CrV bischelates are formed at pH ≤ 5 with the uronic acid bound to CrV through the carboxylate and the -OH group of the furanose form or the ring oxygen of the pyranose form. Six-coordinated oxo–CrV monochelates are observed as minor species in addition to the major five- V VI coordinated oxo–Cr bischelates only for galacturonic acid : Cr ratio ≤ 10 : 1, in 0.25–0.50 M HClO4. At pH 7.5 the EPR spectra show the formation of a CrV complex where the vic-diol groups of Galur participate in the bonding to CrV.
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