Oxalacetate

The reaction probably proceeds through oxalacetic acid as an intermediate HOOCCH(OH)CH OH)COOH HOOCC(OH)=CHCOOH ... 

Make acid yields coumaUc acid when treated with fuming sulfuric acid (19). Similar treatment of malic acid in the presence of phenol and substituted phenols is a facile method of synthesi2ing coumarins that are substituted in the aromatic nucleus (20,21) (see Coumarin). Similar reactions take place with thiophenol and substituted thiophenols, yielding, among other compounds, a red dye (22) (see Dyes and dye intermediates). Oxidation of an aqueous solution of malic acid with hydrogen peroxide (qv) cataly2ed by ferrous ions yields oxalacetic acid (23). If this oxidation is performed in the presence of chromium, ferric, or titanium ions, or mixtures of these, the product is tartaric acid (24). Chlorals react with malic acid in the presence of sulfuric acid or other acidic catalysts to produce 4-ketodioxolones (25,26). 

There are at least eight syntheses of orotic acid in the literature. The most practical in the laboratory is that involving the condensation of diethyl oxalacetate (972) with S-methylthiourea to give 2-methylthio-6-oxo-l,6-dihydropyrimidine-4-carboxylic acid (973) which undergoes either direct acidic hydrolysis or a less smelly oxidative hydrolysis, via the unisolated sulfone (974), to afford orotic acid (971) (B-68MI21303). 

An unusual addition of acetoacetic acid to pyrido[2,3-Z>]pyrazin-2(l//)-one (400) to give (eventually) the 3-acetonyl derivative (401) was postulated (71TH21500) to occur via a cyclic transition state, and the similar addition of oxalacetic ester may occur via a related mechanism. 

Sucrow, studying the chemistry of the enehydrazines (83CB1520), has found several methods for the synthesis of pyrazoles. For example, he has described (79CB1712) the cyclization of monomethylhydrazones of dialkyl oxalacetates to 5-pyrazolones via an enehydrazine (Scheme 47). 

The method of synthesis described for chloropyruvic acid is essentially that reported. This procedure affords the product in excellent yields from readily available materials by a short, convenient route. Other less acceptable methods involve chlorination of pyruvic acid with sulfur dichloride or hypochlorous acid and the treatment of ethyl chloro(l-hydroxyheptyl)- or (o -hydroxybenzyl)oxalacetate 7-lactone with 50% hydrochloric acid. ... 

Oxal-ither, oxalic ether (ethyl oxalate), -essigester, m. oxalacetic ester, -essigsaure, /, oxalacetic acid, -ester, m, oxalic ester (specif, ethyt oxalate),... 

Cyclization of 1-ureidopyrroles 88 with a base gave (79JHC833) pyr-rolo[2,l-/][I,2,4]triazines 89. Pyrolysis of 89 (R2 = COOH) afforded 90. Compounds 88 were prepared by treating chloroacetone semicarbazone 85 with the sodium salts of diethyl oxalacetate or oxalylacetophenone 86 to give semicarbazones 87, which were converted to 88 by the action of hydrochloric acid (Scheme 22). 

For example, glutamic-oxalacetic transaminase activity can be standardized with oxalacetate but not with "convenient" substances such as pyruvate (J ). When reference serums are used, the label value should be confirmed at frequent intervals by the actual method being used routinely, as label values can be in error (19). Conversion factors to convert the results obtained by one method into those obtained by another can give erroneous results and should not be used. 

Schneider, A. J. Willis, H. J. Sources of variation in a standardized and semi-micro procedure for serum glutamic oxalacetic transaminase. Clin. Chem. (1958), 4, 392-408. Atwood, J. G. DiCesare, J. L. Making enzymatic methods optimum for measuring compounds with a kinetic analyzer. Clin. Chem. (1975), n, 1263-1269. 

Amador, E. and sod, M. F. Characterization of the normal serum glutamic-oxalacetic transaminase activity of healthy adults. Am. J. Clin. Path. (1967), 47,... 

Although the metabolism of vanillate generally involves de-O-methylation to 3,4-dihy-droxybenzoate followed by intradiol ring hssion, in Acinetobacter Iwoffii vanillate is hydroxylated to 3-0-methyl gallate, which produces pyruvate and oxalacetate in reactions that have already been noted (Sze and Dagley 1987). 

For 3-chlorobenzoate, an alternative pathway in Alcaligenes sp. strain BR60 may involve 3,4- or 4,5-dioxygenation. Ring fission of the catechols resulted in the production of pyruvate and oxalacetate (Nakatsu and Wyndham 1993). 

The stereoselective catalyzed addition of water or methanol to dimethyl acetylenedicarboxylate (DMAD) was reported to yield oxalacetic acid dimethylester or dimethyl methoxyfumarate. The catalyst precursor cis-[Pd(PMe2Ph)2(solvent)2] [BFJj was prepared from ds-[PdCl2(PMe2Ph)2] and AgBp4 (Eq. 6.54). The analogous platinum complex was not effective, however [99]. 

Acetic, aconitic, ascorbic, benzoic, butyric, caffeic, citric, /j-coumaric, ferulic, fumaric, glutaric, glycolic, glyoxilic, malic, malonic, oxalacetic, oxalic, p-hydroxy benzoic, propionic, succinic, syringic, tartaric, valeric, vanillic Fatty acids... 

Figure 3 Gradient separation of anions using suppressed conductivity detection. Column 0.4 x 15 cm AS5A, 5 p latex-coated resin (Dionex). Eluent 750 pM NaOH, 0-5 min., then to 85 mM NaOH in 30 min. Flow 1 ml/min. 1 fluoride, 2 a-hydrox-ybutyrate, 3 acetate, 4 glycolate, 5 butyrate, 6 gluconate, 7 a-hydroxyvalerate, 8 formate, 9 valerate, 10 pyruvate, 11 monochloroacetate, 12 bromate, 13 chloride, 14 galacturonate, 15 nitrite, 16 glucuronate, 17 dichloroacetate, 18 trifluoroacetate, 19 phosphite, 20 selenite, 21 bromide, 22 nitrate, 23 sulfate, 24 oxalate, 25 selenate, 26 a-ketoglutarate, 27 fumarate, 28 phthalate, 29 oxalacetate, 30 phosphate, 31 arsenate, 32 chromate, 33 citrate, 34 isocitrate, 35 ds-aconitate, 36 trans-aconitate. (Reproduced with permission of Elsevier Science from Rocklin, R. D., Pohl, C. A., and Schibler, J. A., /. Chromatogr., 411, 107, 1987.)...

A carrier molecule containing four carbon atoms (the C4 unit) takes up a C2 unit (the activated acetic acid ), which is introduced into the cycle. The product is a six-carbon molecule (the C6 unit), citric acid, or its salt, citrate. CO2 is cleaved off in a cyclic process, so that a C5 unit is left this loses a further molecule of CO2 to give the C4 unit, oxalacetate. In the living cell, this process involves ten steps, which are catalysed by eight enzymes. However, the purpose of the TCA cycle is not the elimination of CO2, but the provision of reduction equivalents, i.e., of electrons, and... 

There are also voices critical of the rTCA cycle Davis S. Ross has studied kinetic and thermodynamic data and concludes that the reductive, enzyme-free Krebs cycle (in this case the sequence acetate-pyruvate-oxalacetate-malate) was not suitable as an important, basic reaction in the life evolution process. Data on the Pt-catalysed reduction of carbonyl groups by phosphinate show that the rate of the reaction from pyruvate to malate is much too low to be of importance for the rTCA cycle. In addition, the energy barrier for the formation of pyruvate from acetate is much too high (Ross, 2007). 

Another model is based on the fact that the genetic code shows a number of regularities, some of which have already been mentioned above. It is suspected that codons beginning with C, A or U code for amino acids which were formed from a-ketoacids (or a-ketoglutarate, 1-KG), oxalacetate (OAA) and pyruvate. This new model, which is quite different from the previous models, assumes that a covalent complex formed from two nucleotides acted as a catalyst for chemical reactions such as the reductive amination of a-ketoacids, pyruvate and OAA. More recent analyses suggest that the rTCA cycle (see Sect. 7.3) could have served as a source of simple a-ketoacids, including glyoxylate, pyruvate, OAA and a-KG. a-Ketoacids could, however, also have been formed via a reductive acetyl-CoA reaction pathway. The bases of the two nucleotides specify the amino acid synthesized and were retained until the modern three-letter codes were established (Copley et al., 2005). 

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