Pyruvic acid, hydroxy

Acetoxy-17a-hydroxy-5a-pregnane-3,l 1,20-trione (40) is brominated in acetic acid under equilibrating conditions to give a solution of the 2a,4a-di-bromo compound (41). This is reduced by chromous chloride without further treatment, to the 4a-bromo compound (42). The recrystallized bromo compound (42) is then dehydrobrominated via the semicarbazone (43) which is converted without isolation into cortisone acetate (44) by treatment with pyruvic acid ... 

Now at some pH comparable to pK, two waves are observed, corresponding to the reduction of both HA and A. The currents are proportional to the concentrations of the electroreducible species. Because the pH and pK are known, the concentrations of HA and A in the bulk solution can be calculated. It is then found that the observed polarographic currents cannot be accounted for on tbe basis of the known bulk concentrations. It is concluded that the ratio of the concentrations at the electrode surface is different from the ratio of bulk concentrations, and this is a consequence of the coupling between the chemical and electrode processes. In the pyruvic acid system, HA can be converted to the hydroxy acid by the electrode... 

In general, pyruvate decarboxylase (EC 4.1.1.1) catalyzes the decarboxylation of a 2-oxocar-boxylic acid to give the corresponding aldehyde6. Using pyruvic acid, the intermediately formed enzyme-substrate complex can add an acetyl unit to acetaldehyde already present in the reaction mixture, to give optically active acetoin (l-hydroxy-2-butanone)4 26. Although the formation of... 

This is a slow process, and the extraction time depends on the type of extractor used. With stirring as described in Note 10, practically quantitative extraction of jb-hydroxy phenyl pyruvic acid can be achieved within 6 hours. Extremely long extraction times may cause decomposition of the product. 

Sorbic acid has been prepared from crotonaldehyde 1 5 or aldol6 and malonic acid in pyridine solution by hydrogen peroxide oxidation of the condensation product of crotonaldehyde and pyruvic acid 7 and by the action of alkali on 3-hydroxy-4-hexenoic acid,8 9 /3,5-disulfo-w-caproic acid,10 and parasorbic acid.1112... 

Biochemical reactions include several types of decarboxylation reactions as shown in Eqs. (1)-(5), because the final product of aerobic metabolism is carbon dioxide. Amino acids result in amines, pyruvic acid and other a-keto acids form the corresponding aldehydes and carboxylic acids, depending on the cooperating coenzymes. Malonyl-CoA and its derivatives are decarboxylated to acyl-CoA. -Keto carboxylic acids, and their precursors (for example, the corresponding hydroxy acids) also liberate carbon dioxide under mild reaction conditions. 

Photolytic. Sunlight irradiation of 2-methylphenol and nitrogen oxides in air yielded the following gas-phase products acetaldehyde, formaldehyde, pyruvic acid, peroxyacetyl nitrate, nitrocresols, and trace levels of nitric acid and methyl nitrate. Particulate phase products were also identified and these include 2-hydroxy-3-nitrotoluene, 2-hydroxy-5-nitrotoluene, 2-hydroxy-3,5-dinitrotoluene, and tentatively identified nitrocresol isomers (Grosjean, 1984). Absorbs UV light at a maximum wavelength of 270 nm (Dohnal and Fenclova, 1995). 

It may be stated at this point that the presence of a /3-hydroxy-butyrate fat in certain organisms is a matter of general biochemical importance. Usually /3-hydroxybutyric acid and the acetone bodies are derived from n-butyric acid directly. The unambiguous formation of jS-hydroxybutyric acid anhydrides from carbohydrates opens up new vistas its formation from acetaldehyde, and from pyruvic acid, through aldol intermediates can be understood without difficulty. Kirrmann s reaction, to which little attention has been paid, is at the same time an example of an oxygen shift, leading from hydroxyaldehydes to fatty acids. 

The mechanism of this reaction is obscure. One suggested mechanism, analogous to the vapor phase reaction, involves concerted decarboxylation of the pyruvic acid to yield a triplet hydroxy carbene which can either dimerize or attack another molecule of pyruvic acid to yield the observed product.91 Dimerization seems to be the less likely process since the carbene can rearrange to acetaldehyde or react with water. Further, this mechanism predicts that acetoin will be formed when pyruvic acid is irradiated in any solvent that does not possess readily abstractable hydrogen atoms, such as benzene, a solvent in which no reaction is observed. One possible explanation of this discrepancy is that the solvation of the pyruvic acid is extremely different in benzene and in water. However, the specific role that the water plays in the reaction has not been determined. 

Subject Phenylacetic Acid Mandelic Acid o-Hydroxy- phenylacetic Acid Phenyllactic Acid Phenyl- pyruvic Acid p-Hydroxy- phenylacetic Acid... 

When free (W /f. / 1 (-tartaric acid is healed above its melting point, amorphous anhydrides arc formed which, on boiling with water, regenerate the acid. Further heating causes simultaneous formation of pyruvic acid. CHiCOCOOII pyrotartaric acid. llOOrCH C HirH,lCT>OH and. linally. a black, charred residue. In common with other hydroxy organic acids, tartaric acid complexes many metal rons. 

The kinetics of concerted thermal elimination reactions of a series of ethyl (hetero) arylcarboxylate esters (2-thienyl-, 3-thienyl-, 2-furyl, 3-furyl, 4-pyridyl-, 3-pyridyl-, and 2 -pyridylcarbo x y I ate) in the gas phase seem to indicate that there is tittle charge separation in the transition state (83) this is in contrast with the behaviour of the corresponding /-butyl and isopropyl esters for which a semi-concerted transition state (82) was proposed previously.49 Results of a kinetic study of the gas-phase elimination reactions of methylbenzoyl fonnate (84) and 3-hydroxy-3-methylbutan-2-one (85) have been compared with those for pyruvic acid (87) and benzoylformic acid (86).50 The relative rates of reaction [(86)/(87) 46, (87)/(85) = 1.1 x 105 and (86)/(82) = 1 x 106] reveal that the acidity of the hydrogen atom involved in the elimination process, rather than the initial polarization of the C—C bond which undergoes cleavage, is the important rate-controlling factor. 

The application of arylpyruvic acids 256 in place of pyruvic acid in three-component reactions leads to dramatic changes in the direction of the process. Refluxing of starting compounds for 3 hours of irradiating with microwave at 170°C for 20 minutes in acetic acid yielded 3-hydroxy-4,5-diaryl-l-azolyl-2,5-dihydro-li/-2-pyrrolones 258 [203] (Scheme 3.73). Under ultrasonic irradiation in ethanol with the addition of catalytic amounts of hydrochloric acid or in acetic acid, the reaction proceeds in a different direction with the formation of pyrimidinecarboxylic acids 259. In the case of pyruvic acid the course of the three-component reaction does not so drastically depend on the activation method or solvent type as well as from temperature mode [202]. 

Mass spectrometry was used for the structural identification of the fe(3-methyl-4-nitroisoxazol-5-yl) and ethyl ether of 3-methyl-4-nitroisoxazol-5-yl pyruvic acid [1319], the antibacterial compounds 3-(3-methyl-4-nitro-l//-pyrazolc-5-yl)- and 3-(3-methyl-4-nitro-l-a]kylpyrazole-5-yl)-5-methyl-4-nitroisoxazoles[489],7-hydroxy-2-methyl-3-[2-(3-methyl-4-nitro-5-isoxazolyl)-ethyl]-3-hydroxyiminobutyrate and 7-hydroxy-2-methyl-3-[2-(3-methyl-4-nitro-5-isoxazolyl)-l-arylethyl]-chloromones [490], and4-aryl-3-(3-methyl-4-nitroisoxazol-5-yl)-2-pyrazolines [1323],... 

Some preliminary studies were conducted to determine whether one of two proposed reactions could account for the appearance of pyruvate from dalapon. The precursor of pyruvate in this system is probably the a-hydroxy-a-chloropropionate. This compound is unstable and will spontaneously give rise to pyruvic acid. The enzyme apparently forms a-chloro-a-hydroxypropionate from dalapon. One reaction system by which the enzyme could form a-chloro-a-hydroxypropionate from dalapon would involve a direct substitution reaction (Reaction 1). In this case there would be a direct nucleophilic attack at carbon-2, led by a hydroxyl group to form the desired product. 

Disposition in the Body. Readily absorbed after oral administration. It undergoes first-pass acetylation, the extent of which is genetically determined bioavailability 30 to 35% in slow acetylators, 10 to 16% in rapid acetylators. The major metabolites are 3-methyl-l,2,4-triazolo[3,4-a]phthalazine (MTP—the acetylation product) hydralazine pyruvic acid hydrazone (HPH) which is the major plasma metabolite 4-(2-acetylhydra-zino)phthalazin-l-one (A-AcHPZ) which is the major urinary metabolite 3-hydroxymethyl-1,2,4-triazolo[3,4-a]phthalazine (3-OHMTP). About 65% of a dose is excreted in the urine in 24 hours. In rapid acetylators, about 30% is excreted as A-AcHPZ and 10 to 30% as conjugated 3-OHMTP in slow acetylators, about 15 to 20% is excreted as A-AcHPZ and up to 10% as conjugated 3-OHMTP. Other metabolites include phthalazin-1-one (PZ), 1,2,4-triazolo[3,4-fl]phthalazine (TP), 9-hydroxy-MTP, phthalazine, tetrazolo[5,l-a]phthalazine, and hydrazones of hydralazine formed with acetone and a-ketoglutaric acid. About 10% of a dose is eliminated in the faeces. 

While in the presence of 2-oxoglutaric acid neither decarboxylation nor acyloin condensation had been observed, as expected from previously published results (75), we succeeded in the enzymatic conversion of the mono ethyl ester 3 to ethyl 4-oxobutanoate 4, using both whole yeast cells (Saccharomyces cerevisiae) and purified PDC. The oxo ester 4 served as substrate for a second reaction catalyzed by PDC. Formation of a new carbon-carbon bond was accomplished in the presence of pyruvic acid which acted as donor of a C2-unit. Thus, ethyl 4-hydroxy-5-oxohexanoate 5 was obtained for the first time as the result of an enzymatic acyloin condensation. Finally, traces of acid induced the lactonization of hydroxyester 5, indicating it as direct precursor of solerone 1 (Figure 1). 

The biogenesis of solerone 1 and related compounds was successfully rationalized by biomimetic model reactions. As key step we established the pyruvate decarboxylase catalyzed acyloin condensation of pyruvic acid with ethyl 4-oxobutanoate 4 or ethyl 2-oxoglutarate 3 with acetaldehyde. The importance of the ethyl ester function in 3 and 4 serving as substrates for the enzymatic formation of a-hydroxy ketones 5 and 6 was demonstrated. The identification of six yet unknown sherry compounds including acyloins 5 and 6, which have been synthesized for the first time, confirmed the relevance of the biosynthetic pathway. Application of MDGC-MS allowed the enantiodifferentiation of a-ketols and related lactones in complex sherry samples and disclosed details of their biogenetic relationship. 

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