Ketoacids, synthesis

Ju L, Bode JW (2010) Amide formation by decarboxylative condensation of hydroxylamines and alpha-ketoacids synthesis of N-[(lS)-l-phenylethyl]-benzeneacetamide. Organic Synth 87 218-225... 

Synthesis No control is need because only the ketoacid can enolise and the aldehyde is more electrophilic. TM 89 is formed in 80% yield when the two starting materials are mixed in MeOH with KOH at room temperature tHelv. Chim. Acta. 1931,14, 783). 

In addition to /3-diketones, /3-ketoacids and /3-ketoesters, cyanoacetic ester and related compounds are suitable starting materials. The arylhydrazones 4 thus obtained are of great importance as starting materials for the Fischer indole synthesis, as well as for the preparation of other iV-heterocycles. ... 

Ketoacid (1) is an Isomer of a compound made In the book (p T 39) and both were needed for the synthesis of potential fungicides, ... 

In preparation for scale-up of the strigol synthesis described by Sih (8), efforts were made to improve the yield of some of the seven steps involved in the scheme. Of these steps, nine are satisfactory from the standpoint of yield and experimental conditions. For three of the steps, we have improved the yield and/or experimental conditions such that the yield of (+ )-strigol would be raised to 2.85% overall from citral rather than 1.53% based on Sih s procedure and reported yields. Improvements were developed preparation of a-cyclocitral (III), the oxidation of the hydroxyaldehyde (V) to the ketoacid (VII), and for the preparation of the hydroxybutenolide (XVII). For the remaining five steps, our attempts to change experimental conditions have failed to improve, and in most cases to even obtain, the yields reported in the literature (8). We have considered the preparation of strigol analogs and determined the conditions and limitations for the preparation of a series of alkoxybutenolides (XVI) and a butenolide dimer (XVIII). Modification of the literature procedure (11) to eliminate the use of the mesylate (XX) and the use of polar aprotic solvents gave better yields of the 2-RAS (XXI). 

According to de Duve, thioesters on the young Earth were capable of a broad spectrum of chemical reactions for example, of phosphorolysis leading to acylphos-phates (Fig. 7.8a) or of reductive thioester cleavage, which (after carbonylation) made possible the synthesis of ketoacids (Fig. 7.8b). 

Bicyclic lactams 189 are uniquely suited as precursors for the synthesis of chiral substituted 4,5-dihydro-277-pyridazinones 190 by hydrolysis with NH2NH2 and HC1 in dioxane at 85 °C. The reaction gave, as a side product, the ketoacid 191 in some cases (Equation 32) <2003TL7997>. 

A very simple synthesis of the pheromone exo-brevicomin (4i) proceeds via an electrochemical Kolbe condensation between the unsaturated carboxylic acid 39 and the ketoacid 40, followed by hydroxylation of the double bond with OSO4, as... 

In isocitrate, there is a CHOH group that is available for oxidation via the coenzyme NAD+ and the enzyme isocitrate dehydrogenase. NADH will then be reoxidized via oxidative phosphorylation, and lead to ATP synthesis. The oxidation product from isocitrate is oxalosuccinate, a -ketoacid that easily... 

Relatively acidic carbon acids such as malonic esters and jS-keto esters were the first class of carbanions for which reliable conditions for alkylation were developed. The reason being that these carbanions are formed using easily accessible alkoxide ions. The preparation of 2-substiuted /i-kcto esters (entries 1, 4, and 8) and 2-substituted derivatives of malonic ester (entries 2 and 7) by the methods illustrated in Scheme 1.5 are useful for the synthesis of ketones and carboxylic acids, since both /1-ketoacids and malonic acids undergo facile decarboxylation ... 

Enantioselective C-C bond formation is gaining more and more importance in bioorganic synthesis. This reaction is efficiently catalyzed by 2-ketoacid decarboxylases (E.C. 4.1.l.X) as well as by hydroxynitrile lyases (E.C. 4.1.2.X). 

The project encompassed the comparative characterization of pyruvate decarboxylase from Z. mohilis (PDC) and benzoylformate decarboxylase from P. putida (BED) as well as their optimization for bioorganic synthesis. Both enzymes require thiamine diphosphate (ThDP) and magnesium ions as cofactors. Apart from the decarboxylation of 2-ketoacids, which is the main physiological reaction of these 2-ketoacid decarboxylases, both enzymes show a carboligase site reaction leading to chiral 2-hydroxy ketones (Scheme 2.2.3.1). A well-known example is... 

The C-allyl ketoester 69 represents a key precursor for the stereoselective synthesis of the disaccharide analogue 70 in which an ulosonic residue could be installed via the dihydroxylation of the double bond of 69 (equation 98). These glucidic a-ketoacids are involved in biosynthetic pathways of bacteria and constitute important targets for the design of new antibacterial agents. 

Substituted phenylglyoxals (6) are the starting cr-dicarbonyl compounds for the synthesis of 2-arylquinoxalines (7)," and the corresponding aryl a-ketoacids (8) yield 3-aryl-2-quinoxalinones (9)." 12... 

In contrast to transamination reactions that transfer amino groups, oxidative deamination by gutamate dehydrogenase results in the lib eration of the amino group as free ammonia (Figure 19.11). These reactions occur primarily in the liver and kidney. They provide a-ketoacids that can enter the central pathway of energy metabolism, and ammonia, which is a source of nitrogen in urea synthesis. 

D-Amino acid oxidase D-Amino acids (see p. 5) are found in plants and in the cell walls of microorganisms, but are not used in the synthesis of mammalian proteins. D-Amino acids are, hew ever, present in the diet, and are efficiently metabolized by 1he liver. D-Amino acid oxidase is an FAD-dependent enzyme that catalyzes the oxidative deamination of these amino acid isomers. The resulting a-ketoacids can enter the general pathways of amino acid metabolism, and be reaminated to L-isomers, or cafe balized for energy. 

Some of the best-known examples of decarboxylation in organic chemistry include the conversion of 3-ketoacids to ketones in the acetoacetic ester synthesis and the conversion of malonate derivatives to substituted carboxylic... 

However, the key disadvantage of the reaction described in [199] is observed in the first step—synthesis of unsaturated ketoacids 236 with very low yields (20-30%) [200]. The same authors [201] proposed a multicomponent approach to azolopyr-imidinecarboxylic acids. The reactions of pyruvic acid 239 and aromatic aldehydes 240 with 2-aminobenzimidazole, 5-aminotetrazole 156 and 3-amino-1,2,4-triazole 147 in alcohols, DMF and acetic acid were studied (Scheme 3.67). 

---