A-Ketobutyric acid

Biological. Bacterial degradation of 2-methylphenol may introduce a hydroxyl group producing 3-methylcatechol (Chapman, 1972). In phenol-acclimated activated sludge, metabolites identified include 3-methylcatechol, 4-methylresorcinol, methylhydroquinone, a-ketobutyric acid, dihydrox-ybenzaldehyde, and trihydroxytoluene (Masunaga et al, 1986). 

Drosopterin (87a) and isodrosopterin (87b) have been prepared by treatment of 7,8-dihydropterin (593) with p-hydroxy-a-ketobutyric acid (595) or a-hy-droxyacetoacetic acid (601) (506). Their initially proposed structures (507) have been revised to 87 (see Scheme 76) on the basis of detailed, H-NMR spectral analysis of 6,7-dimethyldrosopterin (602), which was prepared by treatment of 7-methyl-7,8-dihydropterin (603) with a-hydroxyacetoacetic acid (601) (50S). Structures of other drosopterins (88-90) have not yet been established. 

Pham, T. T., Guichard, E., Schilch, P., and Charpentier, C. (1995). Optimal conditions for the formation of sotolon from a-ketobutyric acid in the French "vin jaune". ]. Agric. Food Chem. 43, 2616-2619. 

Ketals, of hexitols, IV, 223 Ketene, acetylation of starch with, I, 290 Keto acids, a- and 0-, specificity of carboxylase action on, V, 50 a-Keto acids, aromatic, V, 50 0-Keto acids, oxidation of, II, 148 a-Ketobutyric acid, V, 50 a-Ketocaproio acids, V, 50 Ketogenesis, in liver slices, II, 155 Ketolysis, II, 120, 146, 147, 158 in liver slices, II, 155 Ketolytic, II, 146... 

Several a-keto acids are easily obtained by hydrolysis of acyl cyanides. An improved procedure using cuprous cyanide in the preparation of the acyl cyanides is described. Hydrolysis of the acyl cyanides by cold concentrated hydrochloric acid is described for pyruvic acid (73%), a-ketobutyric acid, and benzoylformic acid (77%). Isovaleryl cyanide is not hydrolyzed under these conditions. Alkaline hydrolysis has been found to be more successful than acid hydrolysis in the preparation of the y-keto acid, a-phenyl-/S-benzoylpropionic acid (76%). ... 

Maleic acid Oxalic acid Citric acid Pyruvic acid Malonic acid a-Ketobutyric acid a-Ketovaleric acid Succinic acid Glycolic acid Lactic acid Formic acid... 

E.39) (E.39) Butanoic acid, 2-oxo-, 2-oxobutanoic acid, 2-oxobutyric acid, a-ketobutyric acid, methylpyruvic acid 600-18-0] FEMA 3733... 

The synthesis was identical to that of G.12, using propanal instead of acetaldehyde (Sulser et al., 1972). The same group (Sulser et al., 1967) previously achieved the synthesis by aldol condensation of a-ketobutyric acid followed by decarboxylation. 

The same authors described a formation pathway from threonine starting by the degradation to a-ketobutyric acid. 

This lactone is the flavoring compound formed by the aging of a-ketobutyric acid (Sulser et al., 1967). The flavor is described as malt, molasses, maple, burnt sugar (Chemisis, 1965), with a strong seasoninglike aroma at a concentration of 0.1 ppm and a taste threshold of 1-5 ppb for Sulser et al. (1972). Manley et al. (1980) reported a maple-like, remarkably persistent curry-like odor and wondered if the enolization or the instability of the compound could be responsible for the two notes. It is a potent odorant of roasted powder and brew of arabica coffee with odor descriptions similar to those of G.12, and an odor threshold of 2-4ng/m , air (Blank et al., 1992a,b), of 7.5 ppb in water (Semmelroch et al., 1995). 

Acetyl a-aminobutyric acid yields a-ketobutyric acid and propionaldehyde in accord with the above formulation. 

Imanari M, Iwane H, Suzuki M, Suzuki N. (1992). Process for preparing a-ketobutyric acid. US Patent 5155263. 

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