Oxalacetic acid

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). 

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

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]. 

SGOT Senna glutamic oxalacetic acid transaminase... 

In the experience of the present author, minor deviations from this procedure may result in decreased yields. Oxalacetic acid of high quality is essential, and this should be verified by a melting-point determination prior to use. Decarboxylation of oxalacetate has been reported111 to occur rapidly at pH 7, and it should be kept to a minimum by maintaining the pH as close to 10 as possible when dissolving the oxalacetic acid. A modification of the Comforth reaction is the co-balt(II)-ion-catalyzed condensation of D-erythrose 4-phosphate with oxalacetate to give 3-deoxyheptulosonic acid 7-phosphate112 (as a mixture of the arabino and ribo isomers). Other procedures for the preparation of KDO will be discussed in subsections 3 and 4 of this Section. 

A modified poly(ethylenimine) also acts as an efficient catalyst for decarboxylation (Suh et al., 1976 Spetnagel and Klotz, 1976). In particular, the partially quaternized polymer [SS] catalyzed the decarboxylation of oxalacetic acid in a bifunctional manner (Spetnagel and Klotz, 1976), as shown in (18). The decarboxylation is thought to occur via pre-equilibrium... 

C-kinetic isotope effects have been used to determine the degree of C —C breakage in metal and non-metal catalyzed decarboxylation of oxalacetic acid. (Sec. 2.2.2). 

Glutamic acid + Oxalacetic acid------- a-Ketoglutaric acid + Aspartic acid... 

Figure 4. Effect of metal ions on nonenzymatic decarboxylation of oxalacetic acid (41)...

Since in the citric acid cycle there is no net production of its intermediates, mechanisms must be available for their continual production. In the absence of a supply of oxalacetic acid, acctaic" cannot enter the cycle. Intermediates for the cycle can arise from the carinxylation of pyruvic acid with CO, (e.g., to form malic acid), the addition of CO > to phosphcnnlpyruvic acid to yield oxalacetic acid, the formation of succinic acid from propionic acid plus CO, and the conversion of glutamic acid and aspartic acid to alpha-ketoglutaric acid and oxalacetic acid, respectively. See Fig. 3. 

No experimental data are available concerning the biosynthesis of 2-desoxyhexoses. The naturally occurring 2-desoxyhexomethyloses (XXII) could be formed, possibly, by condensation of two molecules of acetaldehyde (which can arise from oxalacetic acid or pyruvic acid) and one molecule of glycol aldehyde—that is, from 4-desoxytetroses (XXI) and acetaldehyde. 

However, if a further donor group is introduced, a chelate may be formed that does not involve the carboxylate group to be lost. In these cases, the decarboxylation is dramatically enhanced in the presence of metal ions. This is exactly the situation which pertains with oxalacetic acid, which undergoes a facile metal-promoted decarboxylation (Fig. 5-23). The rate of decarboxylation of oxalacetic acid is accelerated some ten thousand times in the presence of copper(n) salts. The metal ion is thought to play a variety of roles, including the stabilisation of the enolate that is produced after loss of carbon dioxide. 

Figure 5-23. The rate of decarboxylation of oxalacetic acid is accelerated many thousands of times in the presence of metal ions.

Precursors. Precursors for this reaction are compounds exhibiting keto-enol tau-tomerism. These compounds are usually secondary metabolites derived from the glycolysis cycle of yeast metabolism during fermentation. Pyruvic acid is one of the main precursor compounds involved in this type of reaction. During yeast fermentation it is decarboxylated to acetaldehyde and then reduced to ethanol. Acetone, ace-toin (3-hydroxybutan-2-one), oxalacetic acid, acetoacetic acid and diacetyl, among others, are also secondary metabolites likely to participate in this kind of condensation reaction with anthocyanins. 

Isonipecotic acid 4-Piperidinecarboxylic acid Oxalacetic acid Butanedioic acid, oxo-... 

Acetylneuram nic acid. The yield and stereoselectivity of the aldol condensation of 2-acetamido-2-dc.soxy-r>-manno.sc (1) with oxalacetic acid (2) to give N-acetyl-ncuraminic add (3) are improved by adding sodium tetraborate to (he reaction, which is carried out in aqueous solution at pH 10. Thus in the absence of borate ion, yields of (3) ofl 1.5 % have been reported, whereas addition of borate improves the yield to 21.6%. I he borate ion inhibits the alkaline cpimerization of various 2-acylamino-2-desoxy-aldoses. 

In the hydrogenolytic asymmetric transamination between a benzylic amine and oxalacetic acid the Schiff s base was hydrogenated in ethanol over palladium, but alanine rather than aspartic acid was the... 

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