Degradation of sugars

Other possible chemical synthesis routes for lactic acid include base-cataly2ed degradation of sugars oxidation of propylene glycol reaction of acetaldehyde, carbon monoxide, and water at elevated temperatures and pressures hydrolysis of chloropropionic acid (prepared by chlorination of propionic acid) nitric acid oxidation of propylene etc. None of these routes has led to a technically and economically viable process (6). 

WOHL - WEYGAND Aldose degradation Degradation of sugar oximes via cyanohydrins by means of an acid chloride/pyridine (Wohl) or of... 

All known eight-stranded a/p-barrel domains have enzymatic functions that include isomerization of small sugar molecules, oxidation by flavin coenzymes, phosphate transfer, and degradation of sugar polymers. In some of these enzymes the barrel domain comprises the whole subunit of the protein in others the polypeptide chain is longer and forms several additional domains. An enzymatic function in these multidomain subunits, however, is always associated with the barrel domain. 

Thiamine pyrophosphate is a coenzyme for several enzymes involved in carbohydrate metabolism. These enzymes either catalyze the decarboxylation of oi-keto acids or the rearrangement of the carbon skeletons of certain sugars. A particularly important example is provided by the conversion of pyruvic acid, an oi-keto acid, to acetic acid. The pyruvate dehydrogenase complex catalyzes this reaction. This is the key reaction that links the degradation of sugars to the citric acid cycle and fatty acid synthesis (chapters 16 and 18) ... 

The main product of anaerobic degradation of sugars by these organisms is lactic acid. Other products of bacterial carbohydrate metabolism include extracellular dextrans (see p. 40)—insoluble polymers of glucose that help bacteria to protect themselves from their environment. Bacteria and dextrans are components of dental plaque, which forms on inadequately cleaned teeth. When Ca salts and other minerals are deposited in plaque as well, tartar is formed. 

SCHEME 1. A plausible, but incorrect, mechanism for Richardson s oxidative degradation of sugar diethylsulfonyl dithioacetals under basic conditions. 

Some workers have performed hydrolyses in an autoclave, but it has been shown that 0.5 M sulfuric acid at 120° degrades 33% of L-arabinose and 22% of D-galactose in two hours.75 Such methods are, therefore, only suitable for qualitative analyses, unless accurate corrections are made. Similarly, 90% formic acid has been found76 to decompose 48% of D-xylose and 36% of D-galactose in 20 hours at 100°. Gas-liquid chromatography has been used to examine the products formed by the acid degradation of sugars.77... 

The effect of alkoxyl or phosphate groups on the acidic degradation of sugars has not yet been systematically studied. The aldopyranoses substituted at 0-1, that is, the aldopyranosides, are only degraded... 

It has long been known308 that alkaline degradation of sugars gives branched lactones through the benzilic acid type of rearrangement of... 

Stepwise degradation of sugars under catalytic conditions leads to shorter-chain sugars and such by-products as CO, C02, and H20 depending on the conditions (see also next section).348 Sucrose or other carbohydrates have been used for the preparation of new solid acidic catalysts by partial carbonization followed by sulfonation. This leads to sheets of amorphous carbon bearing hydroxyl, carboxyl, and sulfonic groups. These have been used for the production of biodiesel fuel.349... 

MacDonald, D L, Fischer, H O L, The degradation of sugars by means of their disulfones,... 

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