Acetaldehyde, and pyruvic acid

The Doebner reaction can provide the 4-carboxyl quinoline when the Pfitzinger reaction does not." Pfiztinger reaction of pinnacolone with isatin did not provide the desired quinoline. Doebner reaction of aniline with acetaldehyde and pyruvic acid did furnish the quinoline, albeit in only 8% yield. 

Formation of pyranoanthocyanins through reaction of flavylium cations with compounds possessing a polarizable double bond, namely vinylphenol derivatives (including vinylflavanols and hydroxycinnamic acids) and enolizable aldehydes and ketones (e.g., acetaldehyde and pyruvic acid). 

The newest enzyme for use in beer is acetolactate decarboxylase, used to decrease the fermentation time, by avoiding the formation of diacetyl. Externally or internally produced a-acetolactate decarboxylase transforms the a-acetolactate to acetoin (acetylmethylcarbinol) without the enzyme, acetolactate goes to diacetyl, and then a secondary fermentation slowly reduces it to acetoin. Avoiding or reducing the secondary fermentation results in significant reduction in storage capacity and money tied up in inventory Q). Normally acetolactate forms by the thiaminepyrophosphate-catalyzed acyloin condensation of acetaldehyde and pyruvic acid (2) or by the condensation of two pyruvic acid molecules to yield acetolactate and CC. Acetolactate is important in the synthesis of isoleucine and valine by the yeast. The acetolactate left at the end of the primary fermentation is oxidized spontaneously in a nonenzymatic reaction to diacetvl and C0.> (Eqn. 1)... 

Tenscher, A. C. The Kinetics of Sulfite- Hydrogen Sulfite-Binding with Acetaldehyde and Pyruvic Acid. M.S. Thesis, University of California, Davis, CA, 1986, 115 pp. 

In this reaction, a fourth ring was formed, which was considered to be responsible for their higher stability than the original anthocyanins (20). The components which reacted with anthocyanins include 4-vinylphenol, hydroxycinnamic acids, acetone, and several yeast metabolites such as acetaldehyde and pyruvic acid (20-28). 

In reply to the objection that acetaldehyde and pyruvic acid are not so readily fermentable as dextrose, Neuberg suggests that the reaction takes place with one of their tautomeric (enolic) forms. 

From these studies of the concomitant organic products it is clear that the observed G(NHS) values represent the combined yield of a number of different modes of degradation of the peptide chain. And, before proceeding to detailed considerations of elementary processes, it is useful here to formulate working hypotheses as to the stoichiometry of these reactions. First of all we note that the maximal yields of lactic acid and of the carbonyl products, acetaldehyde and pyruvic acid from acetylalanine are obtained only after mild hydrolysis of the irradiated... 

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. 

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). 

Intermediate products which have been identified by isolation or inferred as precursors of butyric acid, butyl alcohol, acetone and isopropyl alcohol are acetaldehyde, acetaldol, pyruvic acid and its aldol,... 

Decarboxylation of a-keto acids is a feature of primary metabolism, e.g. pyruvic acid -> acetaldehyde in glycolysis, and pyruvic acid acetyl-CoA, an example of overall oxidative decarboxylation prior to entry of acetyl-CoA... 

Oxidation of compounds of the types thus far discussed proceeds readily at room temperature. Certain compounds which show no substantial reaction with periodic acid at room temperature can be oxidized at elevated temperature.22- 23 26 Thus, at 100° in aqueous solution the acetone mole exile is split to produce acetic acid and formaldehyde diethyl ketone yields propionic acid and probably ethanol lactic acid gives acetaldehyde and carbon dioxide acetaldehyde is oxidized to formic acid and methanol, which is converted into formaldehyde and pyruvic acid yields acetic acid and carbon dioxide. 

Acetaldehyde, levulic acid, and pyruvic acid also react with furan and 2-methylfuran. Acetoacetic ester reacts, but does not give rise to definite products. Alkylvinyl ethers can be reacted as aldehydes.150... 

Early attempts to cyclize 2-quinolylhydrazones of acetone, acetaldehyde, acetophenone, and pyruvic acid, and a number of 2-pyridylhydrazones, under a variety of conditions failed. Later, however, Robinson and Robinson found that heating 2-methyl-3-hydrazinoquinoline in cyclohexanone gave only a product of uncertain structure described as a dioxide of the hydrazone, but in the presence... 

Efforts to synthesize apoharmine (1, R = Me) by Fischer cyclization of ethyl pyruvate 2-methyl-3-pyridylhydrazone failed, whereas its cyclohexanone hydrazone gave tetrahydroharman (27, R = Me) in 11 % yield on heating with zinc chloride. This yield seems quite low compared to the 94 % yield of a 2 1 mixture of tetrahydro-S-carboline (28) and tetrahydro-j8-carboline (27, R = H), respectively, obtained from cyclohexanone 3-pyridylhydrazone under similar conditions. Okuda and Robison were able to cyclize cyclohexanone 2-pyridyl-hydrazone to 5,6,7,8-tetrahydro-a-carboline in 53 %yield on heating in polyphosphoric acid, but the acetaldehyde, acetone, and pyruvic acid... 

Diacetyl, and its reduction products, acetoin and 2,3-butanediol, are also derived from acetaldehyde (Fig 8D.7), providing additional NADH oxidation steps. Diacetyl, which is formed by the decarboxylation of a-acetolactate, is regulated by valine and threonine availability (Dufour 1989). When assimilable nitrogen is low, valine synthesis is activated. This leads to the formation of a-acetolactate, which can be then transformed into diacetyl via spontaneous oxidative decarboxylation. Because valine uptake is suppressed by threonine, sufficient nitrogen availability represses the formation of diacetyl. Moreover, the final concentration of diacetyl is determined by its possible stepwise reduction to acetoin and 2,3-butanediol, both steps being dependent on NADH availability. Branched-chain aldehydes are formed via the Ehrlich pathway (Fig 8D.7) from precursors formed by combination of acetaldehyde with pyruvic acid and a-ketobutyrate (Fig 8D.7). 

Factors affecting the reaction. The extent of the reactions between anthocyanins and pyruvic acid in model solutions follows a first order kinetic with respect to the anthocyanin disappearance. This reaction is affected by several factors, such as anthocyanin composition, pH, pyruvic acid concentration, temperature and acetaldehyde concentration. The maximum formation took place at pH 2.7-3.0 due to requirement of the anthocyanin fiavylium form, at high pyruvic acid concentration, at low storage temperature (10-15 °C) and in the absence of acetaldehyde (Romero and Bakker 1999a,b, 2000a,b). 

On dissolving orthonitrobenzaldehyde in acetone and adding an excess of dilute caustic-soda solution, indigo blue separates on standing. The acetone may be replaced by acetaldehyde or pyruvic acid. This reaction was studied in detail by Baeyer [44]. The interaction of acetone and orthonitrobenzaldehyde results in the formation of an intermediate product of the compositiop CioHuN04 (probably the methyl ketone of orthonitropheny... 

A wide range of natural and unnatural monosaccharides has been generated by exploiting the catalytic capacity of aldolases which perform reactions equivalent to nonenzymatic aldol additions [54]. More than 20 aldolases have been identified so far and can be divided into three main groups, accepting either dihydroxyace-tone phosphate (DHAP), acetaldehyde, or pyruvic acid, and phosphoenolpyruvate as nucleophilic methylene component. A common feature is their high stereocontrol in the formation of the new C-C bond. As presented in Scheme 10 all four possible vicinal diols are accessible by selection of the appropriate DHAP-aldo-lase [2, 55], all of which show a distinct preference for the two stereocenters and a broad substrate tolerance for the aldehyde component. 

Thiamine anions add to aldehydes and ketones (e.g., acetaldehyde, carbohydrates, and pyruvic acid). Pyruvic acid adducts decarboxylate with a half-life of 24 hours in water and 3.2 minutes in ethanol, since ethanol cannot stabilize the intermediate zwitterion as well as water. After acidification, acetaldehyde is split off. In the adduct between acetaldehyde and thiamine, the electrophilic carbon atom of the aldehyde undergoes an Umpolung " to a resonance-stabilized enolate carbon atom. The thiazole-bound acetaldehyde then functions as carban-ion in Michael additions under mildly basic conditions. Retro-aldo reactions are observed, when 1,3-thiazolium ions react with the carbonyl groups of carbohy-... 

This is an example of nucleophilic catalysis. The aduct from the ylide and pyruvic acid eliminates carbon dioxide to give an enamine which accepts a proton on its exocyclic C-atom. Upon removal of a proton, this intermediate product decomposes to the nucleophilic catalyst and acetaldehyde [99]. 

The presence of Sotolon in foodstuffs has been reported to be the result of an aldol condensation between 2-ketobutyric acid and pyruvic acid 10), similar to the mechanism proposed for the 5-ethyl-3-hydrox> -4-methyl-2(5H)-furanone formation in protein hydrolysates (77). The aldol condensation between acetaldehyde and 2-ketobutyric acid has also been suggested (77) to explain the presence of Sotolon in fortified type wines. 

Several unidentified components in the ethyl acetate fraction were also observed in the reaction mixtures of hydrothermolyzed glucuronic acid and xylose. Unfortunately, isolation attempts were not successful for these products although two were found in moderate amounts. The mass spectra (m/e 164 and 162 from glucuronic acid and xylose, respectively) were not definitive. However, both appeared to be related isomers of the methylchromone(5). When both are compared to 5, one compound (m/e 162) is missing a mass of 18 (possibly water), while the other (m/e 164) is missing a mass of 16 (possibly oxygen). Several other products remained in the aqueous phase after solvent extraction. We presumed that they represented a low molecular weight fraction comprised of formaldehyde, acetaldehyde, crotonaldehyde, acetol, and pyruvic acid, for example (18, ). 

Aerobic living features metabolize sugars and fatty acids to carbon dioxide. Accordingly, there are some kinds of decarboxylation reactions. TPP-mediated decarboxylation of pyruvic acid to acetaldehyde is one of the most important steps of the metabolism of sugar compounds (Fig. 1). When the intermediate reacts with lipoic acid instead of a proton, pyruvic acid is converted to acetylcoenzyme A, which is introduced to TCA cycle (Fig. 2). 

The one-pass yield of pyruvic acid reached 50 mol%. The main side reactions are the formation of acetaldehyde and CO2 by oxydative C-C bond fission of lactic acid and that of acetic acid and CO2 by oxidative C-C bond fission of the produced pyruvic acid. 

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