Glyoxylate degradation and

Ozonization of phenol in water resulted in the formation of many oxidation products. The identified products in the order of degradation are catechol, hydroquinone, o-quinone, cis,ds-muconic acid, maleic (or fumaric) and oxalic acids (Eisenhauer, 1968). In addition, glyoxylic, formic, and acetic acids also were reported as ozonization products prior to oxidation to carbon dioxide (Kuo et al, 1977). Ozonation of an aqueous solution of phenol subjected to UV light (120-W low pressure mercury lamp) gave glyoxal, glyoxylic, oxalic, and formic acids as major products. Minor products included catechol, hydroquinone, muconic, fumaric, and maleic acids (Takahashi, 1990). Wet oxidation of phenol at 320 °C yielded formic and acetic acids (Randall and Knopp, 1980). 

The nitriles can also be employed as intermediates in the condensation of ethyl glyoxylate with aJdehydo sugars under the influence of sodium methoxide, leading to the preparation of L-ascorbic acid and similar compounds. Helferich and Peters described the synthesis of D-ascorbic acid (XXVIII) from tetraacetyl-n-xylononitrile (XXVI) presumably the nitrile underwent a type of ZempMn degradation and the n-threose (XXVII) thus formed condensed with the glyoxylic ester. The method... 

At low temperatures, D-glucose and D-fructose in the presence of ferrous sulfate are converted into D-uru/u770-hexos-2-ulose (36), which can be degraded by further oxidation to glycolic acid, glyoxylic acid, and D-erythronic acid. The nature of the products formed under various conditions and the mechanism of the reaction have been described (see Ref. 1, p. 1133). In dilute solution, in the presence of ferrous sulfate at low temperature, compound 36 gave D-ura mo-2-hexulosonic acid (37) and D-ery//zro-hexo-2,3-diulosonic acid (38). In concentrated solutions, formaldehyde was also found. The formation of these products at low temperature was ascribed to the series of reactions in Scheme 19. 

Many aroma compounds in fruits and plant materials are derived from lipid metabolism. Fatty acid biosynthesis and degradation and their connections with glycolysis, gluconeogenesis, TCA cycle, glyoxylate cycle and terpene metabolism have been described by Lynen (2) and Stumpf ( ). During fatty acid biosynthesis in the cytoplasm acetyl-CoA is transformed into malonyl-CoA. The de novo synthesis of palmitic acid by palmitoyl-ACP synthetase involves the sequential addition of C2-units by a series of reactions which have been well characterized. Palmitoyl-ACP is transformed into stearoyl-ACP and oleoyl-CoA in chloroplasts and plastides. During B-oxi-dation in mitochondria and microsomes the fatty acids are bound to CoASH. The B-oxidation pathway shows a similar reaction sequence compared to that of de novo synthesis. B-Oxidation and de novo synthesis possess differences in activation, coenzymes, enzymes and the intermediates (SM+)-3-hydroxyacyl-S-CoA (B-oxidation) and (R)-(-)-3-hydroxyacyl-ACP (de novo synthesis). The key enzyme for de novo synthesis (acetyl-CoA carboxylase) is inhibited by palmitoyl-S-CoA and plays an important role in fatty acid metabolism. 

Arylthiophens and Di- and Poly-heterocycles. - The reaction of (201) with sulphur gave (202) in 45% yield. Treatment of the hydrazone (203) with PPA at 110°C gave (204), the structure of which was proven by desulphurization of a degradation product with Raney nickel. From the simple phenyl-hydrazone of ethyl 2-thienyl glyoxylate, (205) and (206) were obtained in a 7 3 ratio. Authentic (206) was prepared via the Friedel-Crafts reaction of... 

In other organisms, inciting most fish and amphibians, allantoin is converted into allantoic acid, which is further degraded in two stages to yield 1 molecule of glyoxylic acid and 2 molecules of urea. 

In the tricarboxylic acid cycle acetyl CoA is degraded to COg and reduced pyridine nucleotides (NADH and NADPH, D 16.2). In addition it supplies intermediates for the biosynthesis of the amino acids L-glutamic acid (D 17) and L-aspartic acid (D 16). The carbon chains withdrawn from the cycle by amino acid biosynthesis are replaced by degradation of isocitric acid to succinic acid and glyoxylic acid and the formation of malic acid from the latter. The tri-carboxyhc acid cycle short-circuited by these reactions is known as the glyo-xyhc acid cycle. 

Fig. 181. Degradation of the purine ring system via allantoin to glyoxylic acid and urea 1 Xanthine oxidase or xanthine dehydrogenase 2 urate oxidase 3 allantoinase 4 allantoicase...

Glycine degradation by bovine spermatozoa is thought to go through glyoxylate, formate, and CO2 (Flipse and Benson, 1957). A folic coenzyme, if required here, should be extraordinarily interesting Does the spermatozoon retain the folic coenzyme used in the synthesis of its DNA ... 

Amphibian livers decompose allantoin to urea (278). This process requires two enzymes the first is allantoinase, which hydrolyzes allantoin to allantoic acid, and the second is allantoicase, which cleaves allantoic acid to glyoxylic acid and 2 moles of urea (279-281). Several species of teleost fishes convert allantoin only as far as allantoic acid, but most fishes, amphibia, and fresh water lamellibranchs possess allantoicase as well as allantoinase and degrade allantoin to glyoxylic acid and urea (282). Of interest is the further breakdown of urea to CO2 and NH3, which are the end products of purine catabolism by Crustacea and other lower forms (283). These reactions are shown in Fig. 16. 

In some cases there are similarities between the pathways of purine degradation that are utilized by animals and bacteria. In Pseudomonas, various purines are catabolized to allantoin and then to glyoxylic acid and... 

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