Pyruvic acid conditions

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 ... 

In 1883, Bottinger described the reaction of aniline and pyruvic acid to yield a methylquinolinecarboxylic acid. He found that the compound decarboxylated and resulted in a methylquinoline, but made no effort to determine the position of either the carboxylic acid or methyl group. Four years later, Doebner established the first product as 2-methylquinoline-4-carboxylic acid (8) and the second product as 2- methylquinoline (9). Under the reaction conditions (refluxing ethanol), pyruvic acid partially decarboxylates to provide the required acetaldehyde in situ. By adding other aldehydes at the beginning of the reaction, Doebner found he was able to synthesize a variety of 2-substituted quinolines. While the Doebner reaction is most commonly associated with the preparation of 2-aryl quinolines, in this primary communication Doebner reported the successful use of several alkyl aldehydes in the quinoline synthesis. 

Carboxylic acids with labile a-methylene protons react with isatin in the presence of strong aqueous base. In the total synthesis of methoxatin, the coenzyme of methanol dehydrogenase and glucose dehydrogenase, Weinreb employs a Pfitzinger condensation of an isatin 37 and pyruvic acid as a key step to provide the 4-quinolinic acid 38 in 50% yield under the standard basic conditions. ... 

Only in the case of the pyruvic acid condensation product was it possible to isolate the corresponding ethyl ester under these conditions. This, on mild hydrolysis, reverted to 1-methyl-1,2,3,4-tetrahydro-j8-carbohne-1-carboxylic acid, identical with the starting material, which therefore had the assigned structure 26 (R = CH3) and was not the SchiflF s base 25 (R = CH3). Alkaline hydrolysis of the ester was accompanied by decarboxylation. ... 

As for the reaction path from pyruvic acid to citraconic anhydride, it is considered that a condensation reaction first takes place by a reaction between an oxygen atom of carbonyl group and two hydrogn atoms of methyl group in another molecule, followed by oxidative decarboxylation to form citraconic acid. The produced citraconic acid is dehydrated under the reaction conditions used. The proposed reaction path is shown in Figure 7. 

Pyruvic acid is not stable at ambient temperature when it is stored for a long period of time. It can only be stored in a refrigerated room. A bottle of this acid was stored in a laboratory at 25°C and detonated, probably because of the overpressure created by the formation of carbon dioxide. Indeed, with diacids and complex acids the decomposition is made by decarboxylation. In this particular case, this decomposition should give rise to acetaldehyde. It could be asked whether, in the exothermic conditions of this decomposition, a polymerisation of this aldehyde (see Aldehydes-ketones on p.310) did not make the situation worse. 

The authors chose pyruvic acid as their model compound this C3 molecule plays a central role in the metabolism of living cells. It was recently synthesized for the first time under hydrothermal conditions (Cody et al., 2000). Hazen and Deamer carried out their experiments at pressures and temperatures similar to those in hydrothermal systems (but not chosen to simulate such systems). The non-enzymatic reactions, which took place in relatively concentrated aqueous solutions, were intended to identify the subsequent self-selection and self-organisation potential of prebiotic molecular species. A considerable series of complex organic molecules was tentatively identified, such as methoxy- or methyl-substituted methyl benzoates or 2, 3, 4-trimethyl-2-cyclopenten-l-one, to name only a few. In particular, polymerisation products of pyruvic acid, and products of consecutive reactions such as decarboxylation and cycloaddition, were observed the expected tar fraction was not found, but water-soluble components were found as well as a chloroform-soluble fraction. The latter showed similarities to chloroform-soluble compounds from the Murchison carbonaceous chondrite (Hazen and Deamer, 2007). 

The results obtained appeared quite promising, but the real sensation was the detection of pyruvate, the salt of 2-oxopropanoic acid (pyruvic acid), which is one of the most important substances in contemporary metabolism. Pyruvic acid was first obtained in 1835 by Berzelius from dry distillation of tartaric acid. The labile pyruvate was detected in a reaction mixture containing pure FeS, 1-nonanethiol and formic acid, using simulated hydrothermal conditions (523 K, 200 MPa). The pyruvate yield, 0.7%, was certainly not overwhelming, but still remarkable under the extreme conditions used, and its formation supports Wachtershauser s theory. Cody concludes from these results that life first evolved in a metabolic system prior to the development of replication processes. 

A turnover number of 500 for PDC was obtained after 50 h at which point saturation occurred and the reaction stopped. Under the reaction conditions, between 0.55 and 0.98 jtmol of pyruvic acid were obtained [76]. 

By the beginning of October that year results from Johnson s experiments allowed Krebs to report at a Biochemical Society meeting in Cambridge If pyruvic acid is added to tissues under anaerobic conditions, together with malic acid or oxaloacetic acid, very considerable quantities of citric acid are formed. ... 

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. 

The rate of alanine transamination to pyruvic acid was studied under singleturnover conditions and an 18-fold increase in rate was observed in the pres-... 

The glycolytic pathway, or glycolysis, is a metabolic sequence in which glucose is broken down to pyruvic acid. The subsequent fate of pyruvate then depends upon whether or not the organism is aerobic or anaerobic Under aerobic conditions, pyruvate is oxidized via oxidative phosphorylation under anaerobic conditions, pyruvate is converted further into compounds such as lactate or ethanol, depending upon the organism. 

More drastic hydrolysis conditions of unsaturated oxazolones 448 leads to further hydrolysis of the intermediate 2-acylamino-2-alkenoic acid 449 and produces the corresponding a-keto acids 450. For example, phenylpyruvic acid " and other aryl(heteroaryl)pyruvic acids of biological interest have been obtained in this manner (Scheme 7.148). 

In the majority of dehydration reactions, heterocyclic compounds are formed, rather than carbocyclic compounds. Many possibilities for formation of carbocyclic compounds exist, but these are important only if (a) the heterocyclic or acyclic tautomers cannot undergo further elimination reactions, or (b) the conditions of reaction greatly favor the formation of an acyclic tautomer capable of affording only the carbocyclic compound. Both five- and six-membered carbocyclic compounds have been isolated, with reductic acid being the compound most frequently reported. Ring closure occurs by an inter-molecular, aldol reaction that involves the carbonyl group and an enolic structure. Many examples of these aldol reactions that lead to formation of carbocyclic rings have been studied.47 As both elimination and addition of a proton are involved, the reaction occurs in both acidic and basic solutions. As examples of the facility of this reaction, pyruvic acid condenses spontaneously to a dibasic acid at room temperature in dilute solution, and such 8-diketones as 29 readily cyclize to form cyclohexenones, presumably by way of 30, either in acid or base. 

During strenous exercise there is little oxygen, 02, available for muscle cells. Under these conditions, the muscle cells derive most of their energy from the anaerobic conversion of pyruvic acid, C3H403, into lactic acid, C3H603. The buildup of lactic acid makes the muscles ache and fatigue quickly. Is the pyruvic acid oxidized or reduced as it transforms into lactic acid ... 

Practical and fundamental aspects of malo-lactic fermentation are given. Conditions which winemakers can use for better control of the fermentation, including detailed procedures for inoculation with Leuconostoc oenos ML 34 and for inhibition with fumaric acid, are presented. New information on the role of malic acid decarboxylation in bacterial metabolism and on the enzymatics of malic acid decarboxylation are reviewed. The malic acid decarboxylation seems to involve two pathways a direct decarboxylation of malic to lactic acid with NAD as a coenzyme and a concurrent but small oxidative decarboxylation to pyruvic acid and NADH. How these pathways can bring about the marked stimulation of bacterial growth rate by the malo-lactic reaction and their negligible effect on growth yield are discussed. 

Further developments are shown in Figure 4. On the basis that glucosamine reacted with pyruvic acid in the presence of alkali to yield pyrrole-2-carboxylic acid, in 1% yield, Gottschalk (21) proposed that sialic acid was formed by an aldol condensation reaction between N-ace-tylglucosamine and pyruvic acid. Kuhn and Brossmer (15) and Zilliken and Glick (22) showed that the reverse reaction also took place under alkaline conditions. Cornforth, Firth, and Gottschalk (23) synthesized crystalline N-acetylneuraminic acid (NANA) from N-acetylglucosamine and oxaloacetic acid (pH 11, 20°C). Under conditions less subject to misinterpretation, Heimer and Meyer (24) found that Vibrio cholerae enzymes cleaved NANA into an N-acetylhexosamine and pyruvic acid. 

Similar reactions are undergone by Schiff base derivatives. Thus the Schiff base formed between pyruvic acid and glycine undergoes a similar reaction under weakly basic conditions (Scheme 36).440... 

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