Pyruvic acid catalytic hydrogenation

On addition of the acetic acid, a small amount of black solid settles out, but this dissolves when the solution is swirled for several minutes. The potassium salt of ethyl o-nitrophenyl-pyruvate, although it undergoes no apparent change in color, does not keep indefinitely in the dry state. After 3 weeks of storage at room temperature, the salt still produced a yellow solution when dissolved in acetic acid, but, after 3 months of storage, the dry salt produced a deep-red solution from which an oil, rather than crystalline ester, was obtained after catalytic hydrogenation. 

Reaction of benzo[6]thiophene-2-carboxaldehyde with pyruvic acid yields the keto acid (321), the oxime of which gives a-amino-y-(2-benzo[6]thienyl)butyric acid (322) on catalytic hydrogenation, and j9-(2-benzo[6]thienyl)acrylonitrile on treatment with acetic anhydride the latter yields 8-(2-benzo[6]thienyl)acrylic acid on hydro-... 

The use of proline methyl ester as a chiral auxiliary in the asymmetric synthesis of alanine is shown on the following page. The idea is to start with 2-oxopropanoic acid (pyruvic acid), which has the correct carbon skeleton, and replace tire oxygen on carbon 2 with an amino group and a hydrogen. This must be done in such a manner as to produce only the S-enantiomer of the amino acid, that is, L-alanine. This is accomplished by first attaching a chiral auxiliary, the methyl ester of L-proline, to the acid. In the critical step of the process, the catalytic hydrogenation, the chirality of the... 

This ring closure takes place readily whenever the carbonyl and amino groups occur in the relative positions shown above. Reduction of o-nitro-phenylacetonitrile by stannous chloride produces indole rather than the corresponding amino aldehyde. The synthesis is most useful for the preparation of indole-2-carboxylic acid by reduction of o-nitrophenyl-pyruvic acid with ferrous sulfate and ammonia or with sodium hydrosulfite. The ethyl ester is obtained by a similar reduction with zinc and acetic acid or by catalytic hydrogenation of ethyl o-nitrophenyl-pyruvate over platinum oxide catalyst. ... 

The catalytic hydrogenation of the benzoylformic acid amides of optically active amino acid esters was carried out. When the (5)-amino acid ester was used, the resulting mandelic acid had the (R)-con-figuration. When pyruvic acid amides of optically active benzylic amines were hydrogenated over palladium, optically active lactic acid was obtained in relatively high enantiomeric excess (ee 60%). The... 

Studies on the transamination reaction between f-butyl esters of optically active amino acids and methyl pyruvate were carried out, as shown in Scheme 7. The resulting iminodicarboxylic acid (16) was partially hydrolyzed and then oxidized with f-butyl hypochlorite to form alanine. The oxidation is a generally applicable one, and the optical purity of alanine is high (50-70%). Similar asymmetric transamination between an (S)-amino acid and ketones was carried out. Catalytic hydrogenation of the Schiff s bases prepared from a-keto acid esters and amino acid esters was carried out, and a substituent and temperature effect observed (de 40-70%). ... 

Heterogeneous catalytic hydrogenation of the methyl esters of a-keto acids over modified metal catalysts other than nickel have been studied using a cinchonidine-modified platinum catalyst. " Methyl pyruvate and methyl benzoylformate were hydrogenated to form methyl (R)-lactate and (R)-mandelate with high ee (81-84%). 

Catalytic hydrogenation of the carbonyl group of benzoylformic acid and pyruvic acid bound to an optically active alcohol [(— )-menthol, (+ )-bomeol] or an optically active amine or amino isobutylester yields chiral mandelic acid and lactic acid °. The... 

Asymmetric catalytic hydrogenation of the Schiff base prepared from ethyl pyruvate and an optically active amine in different solvents was carried out and supports the chelation hypothesis. Figure 1 shows solvent effects in the synthesis of alanine and a-aminobutyric acid( ). When (g.)-benzylic cimine was used as the asymmetric moiety, the optical purity of the resulting cotiino acid increased with a decrease in solvent polarity(, 2) A temperature effect was also observed, and the optical purity of the cimino acids increased upon lowering the reaction temperature(, , 10). ... 

In the sequel, we will discuss a generalization of the chelation hypothesis as it applies to reactions other than hydrogenation of Schiff bases of a-keto acids with chiral amines. The catalytic hydrogenation of pyruvic acid amide resulted in the formation of lactcimide in high optical purity (75-99% diastereomeric excess)(] ). This might be explained by the chelate conformation of the substrate-catalyst complex shown in Scheme 8. 

The initial syntheses of Cypridina luciferin and its analogues were performed in low yields by reaction of appropriate 2-aminopyrazines with a-keto acids, followed by reduction with aluminum amalgam or catalytic hydrogenation, and treatment of the product with dicyclohexyl-carbodiimide. For example, 2-amino-5-phenylpyrazine (36) on reaction with pyruvic acid gave the product 37, which was reduced to give an intermediate formulated as 38, which was then cyclized to give the 0x0 compound 39 in 7% yield. It was later discovered that these products could be obtained in high yield in one step by reaction of aminopyrazines such as 36 with a-keto aldehydes such as pyruvaldehyde (MeCOCHO). Condensation of the appropriate aminopyrazine with... 

Besides several diastereoselective heterogeneous catalytic hydrogenations [1-3] only two enantioselective hydrogenation reactions are known the reduction of p-keto-esters with Raney-nickel modified by tartaric acid and of pyruvic acid esters with Pt modified by cinchona alkaloids. Garland and Blaser [4] described the reduction of pyruvic acid ester as a "ligand-accelerated" reaction with the adsorption of the modifier new active sites are generated on the catalyst surface. On these new centers the selective reaction is faster and the increased reaction rate is accompanied by greater enantioselectivities. 

Although cinchona alkaloids and especially cinchonidine, Cnd, proved to be the most effective chiral modifier for the catalytic system of Pt-alumina, in the liquid phase enantioselective hydrogenations of the carbonyl group in pyruvic acid esters, efforts to understand the mechanism of action of this catalyst system has continued to the present. The efforts may be divided into two categories finding natural modifiers other than cinchona alkaloids and examining new effective amino alcohols, which are modeled after the structure of known cinchona modifiers. 

Hiskey and Northrup (1961) have prepared optically active a-amino acids by successive catalytic hydrogenation and hydro-genolysis, starting with an a-keto acid in the presence of an optically active primary amine. The reaction scheme is illustrated in Fig. 20 for pyruvic acid and amino acid of high optical purity are shown in Table III. 

Mizuhara [65] developed a more adequate model by demonstrating that thiamine catalyzes the decarboxylation of pyruvic acid in basic aqueous solution (pH 8.8). Acetoin is the final product of the reaction. Breslow [66] later showed that the hydrogen in position 2 of the thiazole ring of the coenzyme is exchanged with deuterium when deuterium oxide (D2O) is added to the incubation system. Thus, carbon 2 of the thiamine appears to react in this chemical process. The hydrogen in position 2 is acidic and is thus readily ionized to an anion in basic media (see Fig. 4-7). On the basis of these findings, researchers have proposed the following sequence of reactions to explain the catalytic action of carboxylase. The carbon 2 of the thiazo-... 

Ochoa s attention was next concentrated upon one of the central issues of that period the mechanisms of oxidative degradation of pyruvic acid to CO2 and H2O. In the previous decades, Torsten Thunberg had discovered the oxidative capacity of tissue extracts for a number of dicarboxylic acids. Albert Szent-Gyorgyi had observed the catalytic effect of succinic, fumaric, malic and oxaloacetic acids in the respiratory process and related these observations to the metabolism of carbohydrates. The oxidative process implied the formation of CO2 and hydrogen, the latter being eventually accepted by respiratory oxygen to form water with the participation of cytochrome. 

For example, the Pt-alumina-alkaloid catalytic systems proved to be the best for enantioselective hydrogenations of 2-oxocarboxylic acids and their esters, especially the pyruvates (Blaser Baiker ), and the formates (Orito et al. ), originally studied in the "Orito Reaction" (see Bartok et... 

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