Release Of Aldehyde Research Articles

Substituted 1,3,5-Triazaadamantanes: Biocompatible and Degradable Building Blocks

Substituted 1,3,5-Triazaadamantanes: Biocompatible and Degradable Building Blocks

Reduction of Carboxylic Acids by Nocardia Aldehyde Oxidoreductase Requires a Phosphopantetheinylated Enzyme

Aldehyde oxidoreductase (carboxylic acid reductase (Car)) catalyzes the magnesium-, ATP-, and NADPH-dependent reduction of carboxylic acids to their corresponding aldehydes. Heterologous expression of the car gene in Escherichia coli afforded purified recombinant enzyme with a specific activity nearly 50-fold lower than that of purified native Nocardia sp. enzyme. The 5-fold increase in specific activity obtained by incubating purified recombinant Car with CoA and Nocardia cell-free extracts indicated that post-translational phosphopantetheinylation of Car is required for maximum enzyme activity. Nocardia phosphopantetheine transferase (PPTase) expressed in E. coli was isolated and characterized. When incubated with [(3)H]acetyl-CoA and Nocardia PPTase, the labeled acetylphosphopantetheine moiety was incorporated into recombinant Car. Coexpression of Nocardia Car and PPTase in E. coli gave a reductase with nearly 20-fold higher specific activity. Site-directed mutagenesis in which Ser(689) was replaced with Ala resulted in an inactive Car mutant. The results show that Car expressed in Escherichia coli is an apoenzyme that is converted to a holoenzyme by post-translational modification via phosphopantetheinylation. Doubly recombinant resting E. coli cells efficiently reduce vanillic acid to vanillin.

Effect of whey protein on the in vivo release of aldehydes.

Retention of aldehydes by whey proteins in solutions buffered at a range of pH values was studied under static and dynamic headspace conditions and in vivo in exhaled air. Static headspace measurements showed a clear increase in retention in the presence of whey proteins for aldehydes with longer carbon chains and for buffer solutions with higher pH values. For in vivo aldehyde release measurements, these effects were much less pronounced. The presence of saliva or the binding of aldehydes to the surface of the oral cavity was not responsible for this effect. This difference can be explained by the highly dynamic conditions of in vivo aroma release of liquid products, due to the relatively large flow of air during exhalation. After swallowing, a thin film of aldehyde solution remains in the pharynx; subsequent exhalation will release both the free aldehydes present in this film and those reversibly bound to the whey protein.

Theoretical Study on the Mechanism of Catalysis of Coenzyme B12-Dependent Diol Dehydratase

The energy profile of the diol dehydratase reaction is discussed from theoretical calculations at the B3LYP/6-311G* level of density functional theory. The differences between the energy diagrams of models with and without K+ ion are rather small except for the substrate binding and the OH group migration. The most important role of K+ ion in the diol dehydratase catalysis is to fix substrates and intermediates in proper positions in order to ensure the hydrogen abstraction and recombination between them and the adenosyl group. In the course of the reaction, substrates and reaction intermediates would always be kept bound to K+ ion until the release of product aldehyde from the active site. Given the neutral radical state of the substrate, the OH group migration proceeds in a concerted mechanism. In this process, K+ ion can work as an inhibitor of intramolecular hydrogen bond, which decreases the activation energy by 4.0 kcal/mol, due to the destabilization of reactant 1,2-dihydroxypropyl radical. The low...

Ruthenium-catalyzed hydration of 1-alkynes to give aldehydes: insight into anti-Markovnikov regiochemistry.

The mechanism of the selective conversion of 1-alkynes to aldehydes by hydration was investigated by isolating organic and organometallic byproducts, deuterium-labeling experiments, and DFT calculations. The D-labeled acetylenic hydrogen of 1-alkyne was found exclusively in the formyl group of the resulting aldehydes. After the reaction, the presence of metal-coordinated CO was confirmed. All of the experimental results strongly suggest the involvement of a metal-acyl intermediate with the original acetylenic hydrogen also bound to the metal center as a hydride, with the next step being release of aldehyde by reductive elimination. Theoretical analyses suggest that the first step of the catalytic cycle is not oxidative addition of acetylene C [bond] H or tautomerization of eta(2)-alkyne to a vinylidene complex, but rather protonation of the coordinated 1-alkyne at the substituted carbon to form a metal-vinyl intermediate. This cationic intermediate then isomerizes to Ru(IV)-hydride-vinylidene via alpha-hydride migration of the vinyl group to the metal center, followed by attack of the vinylidene alpha-carbon by OH(-) to give the metal-hydride-acyl intermediate.

ChemInform Abstract: Efficacious Modification of the Procedure for the Aldehyde Release from 2‐Substituted Thiazoles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

2-Thiazolyl α-Amino Ketones: A New Class of Reactive Intermediates for the Stereocontrolled Synthesis of Unusual Amino Acids

The thiazole-based one carbon homologation of four α-amino acids (L-phenylalanine, L-leucine, L-threonine, and L-serine) to the corresponding α-hydroxy β-amino aldehydes and acids in both configurations at Cα, is described. The methodology involves the following key operations: (i) the conversion of an α-amino ester to a 2-thiazolyl α-amino ketone; (ii) the stereocontrolled reduction of a ketone carbonyl to either syn or anti α,β-amino alcohols; (iii) the aldehyde release from the thiazole ring; (iv) the oxidation of the aldehyde to a carboxylic acid. The methodology was only partially applied to L-phenylglycine because of some limitations in operation (i).

Efficacious modification of the procedure for the aldehyde release from 2-substituted thiazoles

Efficacious modification of the procedure for the aldehyde release from 2-substituted thiazoles

ChemInform Abstract: Organic Synthesis with Sulfur Heterocycles (Thiazoles) as Auxiliaries. The Thiazole Route to Carbohydrates and Biologically Active Derivatives

Abstract Functionally-substituted thiazoles at C-2, namely 2-trimethylsilylthiazole (2-TST), 2-thiazolylmethylenetriphenylphosphorane (2-TMP) and 2-thiazolylcarbonitle N-oxide (2-TNO) serve as effective auxiliaries in new synthetic strategies for the stereoselective synthesis (THIAZOLE ROUTE) of long-chain protected polyhydroxyaldehydes, i.e. carbohydrate-like materials, starting from readily available precursors such as chiral hydroxy- and aminoaldehydes. These methodologies are based on two essential operations, both chemically and stereochemically very efficient; i) the coupling between the functionally-substituted thiazole and an appropriate substrate by a carbon-carbon bond forming reaction; ii) the aldehyde release in the resulting adduct by thiazole into formyl conversion. Some compounds obtained in this way are transformed by functional group elaborations into molecules of biological relevance such as deoxy- and aminosugars, and sphingosines.

Organic Synthesis with Sulfur Heterocycles (Thiazoles) as Auxiliaries. The Thiazole Route to Carbohydrates and Biologically Active Derivatives

Abstract Functionally-substituted thiazoles at C-2, namely 2-trimethylsilylthiazole (2-TST), 2-thiazolylmethylenetriphenylphosphorane (2-TMP) and 2-thiazolylcarbonitle N-oxide (2-TNO) serve as effective auxiliaries in new synthetic strategies for the stereoselective synthesis (THIAZOLE ROUTE) of long-chain protected polyhydroxyaldehydes, i.e. carbohydrate-like materials, starting from readily available precursors such as chiral hydroxy- and aminoaldehydes. These methodologies are based on two essential operations, both chemically and stereochemically very efficient; i) the coupling between the functionally-substituted thiazole and an appropriate substrate by a carbon-carbon bond forming reaction; ii) the aldehyde release in the resulting adduct by thiazole into formyl conversion. Some compounds obtained in this way are transformed by functional group elaborations into molecules of biological relevance such as deoxy- and aminosugars, and sphingosines.

Determination of the release rate of aldehyde pheromones from insect lures by cold trapping and direct bioluminescence analysis

A rapid and sensitive procedure for measuring the release rate of aldehyde pheromones from insect lures has been developed. Using cold traps to condense aldehydes released into an airstream, the amount of pheromone in the aqueous condenstate could be directly analyzed using a luminescence assay based on the response of bacterial luciferase to long chain aldehydes. A high recovery (∼70%) of aldehyde pheromone in the cold trap was obtained even when amounts as low as 10 ng were released into the airstream. Trapping times as low as 5 min can be used and analysis requires only a few seconds after temperature equilibration of the sample. This approach was applied to measure the release rate of 11-tetradecenal from different spruce budworm lures as well as to demonstrate that the release of aldehyde from a lure containing [ 14C]- cis-9-hexadecenal correlated closely to the release rate of radioactive material.

Carbon 13 magnetic resonance studies of DL-2-(alpha-hydroxyethyl) thiamin and related compounds. Relation of kinetic acidity to electronic factors in thiamin catalysis.

Carbon 13 NMR spectra have been obtained for aqueous solutions of DL-2-(alpha-hydroxyethyl)thiamin, DL-2-(alpha-hydroxybenzyl)thiamin, DL-2-(alpha-hydroxybenzyl)oxythiamin, and related N-3 methyl and N-3 benzyl analogs. The unusually large downfield shift of the 13C resonance of C-2 of hydroxyethylthiamin suggests that this carbon bears a partial positive charge. This result stands in contrast to results of x-ray crystallographic studies of hydroxyethylthiamin, which place a partial negative charge on C-2 (Pletcher, J., and Sax, M. (1974) J. Am. Chem. Soc. 96, 155-165). A partial positive charge on C-2 helps to explain the facility of carbanion formation at the alpha carbon both enzymatically and in model systems. The rates of proton-deuteron exchange of (C-alpha)-H with solvent deuterium, and of release of aldehyde to regenerate thiamin have been measured for hydroxyethylthiamin and analogs. The differences in kinetic acidity of (C-alpha)-H and of rates of aldehyde release are rationalized in terms of differing electron-withdrawing abilities of the substituents attached to N-3, and appear not to be related to intramolecular basic catalysis of these processes by the C-4' amino group.

Kinetic studies on oxidized nicotinamide--adenine dinucleotide-facilitated reactions of D-glyceraldehyde 3-phosphate dehydrogenase.

The kinetics of the acylation of d-glyceraldehyde 3-phosphate dehydrogenase from pig muscle by 1,3-diphosphoglycerate in the presence of NAD(+) has been analysed by using the relaxation temperature-jump method. At pH7.2 and 8 degrees C the rate of acylation of the NAD(+)-bound (or holo-) enzyme was 3.3x10(5)m(-1).s(-1) and the rate of phosphorolysis, the reverse reaction, was 7.5x10(3)m(-1).s(-1). After a temperature-jump perturbation the equilibrium of NAD(+) binding to the acyl-enzyme was re-established more rapidly than that of the acylation. The rate of phosphorolysis of the apoacylenzyme from sturgeon muscle and of aldehyde release from the d-glyceraldehyde 3-phosphate-apoenzyme complex were </=40m(-1).s(-1) and </=12s(-1) respectively at pH8.0 and 22 degrees C, which means that both processes are too slow to contribute significantly to the reaction pathway of the reversible NAD(+)-linked oxidative phosphorylation of d-glyceraldehyde 3-phosphate. Phosphorolysis of both acyl-apoenzyme and acyl-holoenzyme was first-order in P(i) up to 100mm-P(i) and more. PO(4) (3-) could be the reactive species of the phosphorolysis of the acyl-holoenzyme, in which case phosphorolysis is a diffusion-controlled reaction, although other kinetically indistinguishable rate equations for the reaction are possible.