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Nonribosomal depsipeptides are natural products composed of amino and hydroxy acid residues. The hydroxy acid residues often derive from α-keto acids, reduced by ketoreductase domains in the depsipeptide synthetases. Biochemistry and structures reveal the mechanism of discrimination for α-keto acids and a remarkable architecture: flanking intact adenylation and ketoreductase domains are sequences separated by >1,100 residues that form a split 'pseudoAsub' domain, structurally important for the depsipeptide module's synthetic cycle.

Six optically active macroheterocycles bearing ester and dihydrazide moieties were synthesized from available natural (-)-α-pinene through the intermediate keto acid, (31R,33R)- 1-hydroxy-32,32-dimethyl-1,4-dioxopentaphane, using the [2+1] reaction of this keto acid with di- or triethylene glycols and the [1+1] condensation of the resulting α,ω-diketo diesters with dicarboxylic acid dihydrazides in the key steps.

Procedures for the analysis of free alpha-keto acids in human fluids (i.e. plasma, cerebrospinal fluid, urine, etc.) as well as for studying the dynamic free alpha-keto acid pools in differentiated tissues and organ cells have been the subject of growing clinical interest in the study of metabolic regulatory and pathophysiological phenomena. Due to the high instability and polarity of the alpha-keto acids being examined, the development of a quantitative and reproducible analysis of metabolically relevant intracellular alpha-keto acids still presents a substantial methodological challenge. The aim of small sample size, rapid, non-damaging and "metabolism-neutral" cell isolation, careful sample preparation and stability, as well as reproducible analytics technology is not often achieved. Only few of the methods described can satisfy the rigorous demands for an ultra-sensitive, comprehensive and rapid intracellular alpha-keto acid analysis.

A facile single-step synthesis of the title isocoumarins isolated from Xyris indica has been elaborated. Condensation of butanoyl chloride and 2-oxobutanoyl chloride with 3,4-methylenedioxyhomophthalic acid afforded xyridin A and xyridin B, respectively. Xyridin A was saponified to the corresponding keto acid, which on reduction gave the (±)-3,4-dihydro-6,7-methylenedioxy-3-propylisocoumarin in which diastereotopy of the methylenic protons around the stereogenic center was observed. A mass fragmentation mechanism for xyridins has also been suggested.

Recent advances in computational approaches for creating pathways for novel biochemical reactions has motivated the development of approaches for identifying enzyme-substrate pairs that are attractive candidates for effecting catalysis. We present an improved structural-based strategy to probe and study enzyme-substrate binding based on binding geometry, energy, and molecule characteristics, which allows for in silico screening of structural features that imbue higher catalytic potential with specific substrates. The strategy is demonstrated using 2-keto acid decarboxylation with various pairs of 2-keto acids and enzymes. We show that this approach fitted experimental values for a wide range of 2-keto acid decarboxylases for different 2-keto acid substrates. In addition, we show that the structure-based methods can be used to select specific enzymes that may be promising candidates to catalyze decarboxylation of certain 2-keto acids. The key features and principles of the candidate enzymes evaluated by the strategy can be used to design novel biosynthesis pathways, to guide enzymatic mutation or to guide biomimetic catalyst design.

2-Cetyl-3-20 keto acid(N-ethyl perfluorinated octyl sulfonamide) N- ethyl ester was synthesized by the reaction of N-ethyl-N-hydroxyethyl perfluorinated octyl sulfonamide and alky ketene dimer. The experimental results show that the yield of products can be 89% when the molar ratio of perfluorinated octyl sulfonamide to ketene dimer is 1:1.1 and the reaction lasts about four hours at 80 °C. The structure of the product was characterized by FTIR and 1HNMR. The product can dissolve in polar solvents such as NMP, DMAC, THF, DMSO, CHCl3, and 10% weight-loss temperature measured by TGA is 202 °C.

2-Arylidene-cyclohexanone1, -cyclopentanone2, -1-indanone3 and-1-tetralone4 react with acetoacetanilide5 yielding 2-oxo-4-aryl-3-carboxylic acid anilides derivatives of naphthalene7, indene8, fluorene9 and phenanthrene10. Reaction of1 and3 with benzoylacetanilide6 yields the corresponding Michael adducts11 and12.

Lack of both phosphorus and potassuium results in accumulation of all the keto acids and amino acids in 30 days and 20 days old peanut leaves respectively. This is due to te sluggish metabolism of the tissue under P and K deficienty. Decrease of all the keto acids in 20 days old plants suggests that their synthesis might be affecte under P and K deficiency.

Electrophoretic studies showed that 3-hydroxybutyrate dehydrogenase and aspartate aminotransferase patterns may prove useful for characterising Rhizobium strains. Although a relatively small number of strains was tested in this study, it was interesting thatR. trifolii andR. leguminosarum had similar patterns of both enzymes. Some preliminary studies on the possible roles of the three forms of aspartate aminotransferase in soybean nodules are also presented.

The stimulating effect of ascorbic acid, administered to colchicine-treated mycelia ofCunninghamella elegans, on respiration, keto acid production and carbohydrate accumulation was lower than the highly increased rate of sugar absorption. Furthermore, the increasing ascorbic acid concentration in colchicine media favoured lower carbohydrate accumulation, keto acid production, carbon dioxide output and highly stimulated the utilization of the absorbed sugars for the formation of non-carbohydrate compounds. In addition, the vitamin seemed to counteract the inhibitory effects of colchicine on nucleoprotein and soluble nucleotide synthesis by colchicine-treated mycelia particularly when the drug was administered at high levels.

The organism grown on Δ1-p-menthene was found to grow without any lag on methyl isopropyl ketone, isobutyrate, succinate, malate, lactate and acetate. Isobutyrate or acetate grown cells grew on Δ1-p-menthene after a lag and showed comparatively little growth on β-isopropyl pimelic acid.

The reaction of 3-phenylethynyl-2-quinoxalones with aliphatic and aromatic amines gives alkyl(aryl)imines of 3-phenacylidene-2-quinoxalone, the structures of which were proved by alternative synthesis from 3-phenacylidene-2-quinoxalone and the appropriate amines.

BeiPapaver somniferum L. wurde im Laufe der Ontogenese die Anwesenheit von Ketosauren des Zitronensaurecyclus verfolgt. Zur Blutezeit und nach dem Verbluhen konnten auch die aromatischen Ketosauren, Phenylbrenztraubensaure undp-Hydroxyphenylbrenztraubensaure nachgewiesen werden (2,4-Dinitrophenylhydrazone und nach Reduktion zu Aminosauren: Phenylalanin und Tyrosin).

THE nickel reaction, discovered by Katsuki et al.1, produces a red colour with pure cis isomers of α-keto-acid-2,4-dinitrophenylhydrazones and differentiates them from their corresponding trans isomers. We have found that this reaction applies to isomeric differentiation of the keto-acid hydrazones on paper chromatograms by the following procedures

DURING a study of plant keto-acids carried out by one of us (G. H. N. T.) under the direction of Prof. F. C. Steward at Cornell University, an unknown substance, hereafter designated compound I, was found in the keto-acid fraction of all plant tissues examined1. This substance was isolated in crystalline form (sint. 206°, decomp. 214°) from the keto-acid dinitrophenylhydrazone fraction of Mentha piperita leaves by elution from an alumina column with 1 per cent sodium carbonate. Its position on chromatograms was similar to that of the slower-moving spot of pyruvic acid dinitrophenylhydrazone (Fig. 1, ref. 1). The pyruvic acid spot developed a chocolate colour when sprayed with alkali, whereas compound I gave a yellow colour. On hydrogenation, compound I yielded a ninhydrin-reactive substance (compound II) which was chromatographically similar to γ-amino-butyric acid (Fig. 2, ref. 1). The infra-red absorption spectrum of compound I did not display the carboxyl peak characteristic of α-keto-acid dinitrophenyl-hydrazoness.