A-Ketovaleric acid

Thus we designed and synthesized a bicyclic pyridoxamine derivative carrying an oriented catalytic side arm (16) [11], Rates for conversion of the ketimine Schiff base into the aldimine, formed with 26 (below) and a-ketovaleric acid, indolepyruvic acid, or pyruvic acid, were enhanced 20-30 times relative to those carried out in the presence of the corresponding pyridoxamine derivatives without the catalytic side arm. With a-ketovaleric acid, 16 underwent transamination to afford D-norvaline with 90% ee. The formation of tryptophan and alanine from indolepyruvic acid and pyruvic acid, respectively, showed a similar preference. A control compound (17), with a propylthio group at the same stereochemical position as the aminothiol side arm in 16, produced a 1.5 1 excess of L-norvaline, in contrast to the large preference for D-amino acids with 16. Therefore, extremely preferential protonation seems to take place on the si face when the catalytic side arm is present as in 16. 

Ketosis, relation to carbohydrate oxidation, II, 145-159 theory of, II, 146 a-Ketovaleric acids, V, 50 Konigs-Knorr reaction, I, 79, 114 a-glycoside formation in, I, 84 Kojic acid, III, 373 from sucrose, IV, 322, 324... 

D-Amino oxidase is a peroxisomal enzyme that catalyzes the oxidative deamination of D-amino acids to give the corresponding a-keto acids, ammonia, and hydrogen peroxide. In this assay, a-ketovaleric acid from D-valine was quantitated. 

The quinoxalinol derivatives of a-ketovaleric acid and ketovaleric acid (internal standard) were separated on a LiChrospher 100 RP-8 column (4 mm x 250 mm). The mobile phase was a 60 40 ratio of 0.35 Af ammonium acetate and acetonitrile. The eluate was monitored by fluorescence with the excitation and emission wavelengths set at 340 and 420 nm, respectively. 

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

DL-Norvaline-3-C on administration to rats or on incubation with rat liver homogenates yielded radioactive a-ketovaleric acid, butyric acid, acetic acid, acetoacetate, and 3-hydroxybutyric acid HI). These compounds were isolated by column cluomatography and their identity established. Degradation of the butyric acid demonstrated that only C-2 was significantly labeled. This established that the butyrate was formed by a direct pathway from norvaline and not by the subsequent condoisation of two-carbon fragments. 

The conversion of a cycloheptanone to a bicyclo[5.3.0]decane derivative can be effected through ring opening of an intermediate furfurylidene derivative (57JA6023). Thus, condensation of 2-methylcycloheptanone with furfuraldehyde in the presence of sodium methoxide gave (61). On heating with concentrated hydrochloric acid in ethyl alcohol, the ketovaleric acid (62) was produced which on aldolization furnished the bicyclic ketone (63) in 17% overall yield (Scheme 15). 

The reaction mixture contained in 1.0 mL 20 /tinol of D-Val, 10 nmol of FAD, 10 fig of catalase, and 2 nmol of ketovaleric acid in 0.1 Af pyrophosphate buffer (pH 8.5). The enzymatic reaction was started by adding 10 to 100 fiL of beef kidney homogenate. At different times, 200 fiL aliquots were withdrawn and added to 100 fiL of ice-cold 6 Af HC1. After centrifugation, a... 

Upon incubating DL-norleucine-3-C with rat liver homogenate the radioactive products obtained were a-ketocaproic acid, valeric acid, and /S-hydroxyvaleric acid 140). The further oxidation of (8-hydroxyvaleric acid results in the formation of /3-ketovaleric acid then of acetic and propionic acids. The results support the scheme of catabolism shown in Fig. 10. 

In this communication we extend our prior observations and demonstrate the use of xylan-rich, hemicellulosic residual fractions of wood for the production of P(3HB-co-3HV) by B. cepacia. Levulinic acid, the secondary carbon source utilized in this bioconversion process, can be produced cost-effectively from a vast array of renewable carbohydrate-rich resources including cellulose-containing forest and agricultural waste residues 24,25). This five-carbon cosubstrate (4-ketovaleric acid) serves as a precursor to the 3-hydroxyvalerate (3HV) component of the B. cepacia-dtnved P(3HB-co-3HV) copolymer (Figure 1). Further, the mol % 3HV composition and associated physical/mechanical properties of the copolymer can be manipulated as a function of the substrate concentrations provided in the fermentation. Physical-chemical characterizations of such PHA copolymers are reported herein, as evidence supporting the potential of these biodegradable thermoplastics to serve as viable replacements for conventional, environmentally recalcitrant commodity plastics. 

Similar results were obtained on reduction of 3,4,5-trimethylisoxa-zole/ Further examples of such a cleavage were found later. Thus, j8-(3-halogenoisoxazol-5-yl) propionic acids (163) on treatment with sodium amalgam give a mixture of S-cyano-y-ketovaleric and succinic acids (163—> 164) The reaction can be interpreted as a result of... 

The hydrolysis of succinyl CoA permits a-ketoglutarate oxidation to proceed to completion in the presence of catalytic quantities of CoA, but it results in a waste of the potentially useful thioester bond. One use for the thioester group is to permit metabolism of certain jS-keto acids. A CoA transferase isolated from pig heart is absolutely specific for succinate and succinyl CoA, but only relatively specific for the 8-keto acid (XIV). The rate of reaction is greatest with acetoacetate, and decreases as the chain length is increased from 8-ketovalerate to 8-ketocaproate. Longer chains are not used. Branched chain /3-keto acids can also serve as substrates, but ,j3-unsaturated acids, /3-hydroxy acids, and dicar-boxylic acids cannot accept CoA in this transfer reaction. An enzyme... 

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