Reaction Of Pyridoxal Research Articles

Synthesis, characterization, and applications of novel Co(II)‐pyridoxalphosphate‐Schiffbase/SBA‐15 as a nanocatalyst for the green synthesis of benzothiazole heterocycles

AbstractMesoporous heterogeneous santa barbara amorphous (SBA)‐15‐supported cobalt complex, as a novel nanocatalyst containing N–O chelating Schiff‐base ligand was successfully synthesized by the reaction of SBA‐15 and Cobalt(II)‐Schiff‐base complex. The Co(II)‐Schiff base complex also was prepared for the first time, by the reaction of pyridoxal 5′‐phosphate or PLP (biological active form of vitamin B6), 3‐(aminopropyl)‐triethoxysilane in methanol that complexation with CoCl2. The subsequent grafting of entitled complex to SBA‐15 afforded Co(II)‐PLP‐Schiff base/SBA‐15 mesoporous catalyst. Characterization of the product was carried out with powder X‐ray diffraction, Brunauer–Emmett–Teller nitrogen adsorption–desorption, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, atomic absorption spectroscopy, and inductively coupled plasma, Fourier‐transform infrared spectroscopy. The results revealed the retention of the textural properties and hexagonally uniform structures of SBA‐15 during the grafting procedure. This nanocatalyst was applied successfully for one‐pot synthesis of various benzothiazole heterocycles under green conditions. This catalyst is an active, reusable, and stable nanomaterial with no leaching of metal ions to the reaction medium. It was used for the synthesis of desired benzothiazole heterocycles by the cyclo‐condensation of aryl‐aldehydes with 2‐aminothiophenol with good to excellent yields and under green conditions.

Reactions of pyridoxal with aromatic diamines

Pyridoxal monoimines were obtained by the reaction of pyridoxal with aromatic diamines. A change in the ratio of the reagents or introduction of another aromatic aldehyde into the reaction leads to the formation of symmetric and asymmetric diimines. In some cases, the initially formed diimines are transformed into the corresponding benzimidazoles. The products of the reaction of pyridoxal with 1,3-diaminobenzene have a furopyridine structure.

Reactions of Pyridoxal with Heterocycles Containing Primary Amino Group

New nitrogen-containing derivatives of pyridoxal were obtained as a result of its reaction with various amines. The reactions with amines bearing a heterocyclic fragment (pyridine, pyrimidine, quinoline, piperidine) furnished the final products stabilized in an aminoacetal form. The product prepared from 2-aminomethylpiperidine has an imidazolidine fragment in the molecule.

Combination of nutrients in a mammalian cell culture medium kills cryptococci.

We found that a large inoculum of Cryptococcus gattii cells, when plated on Dulbecco's modified eagle's medium (DMEM) incorporated into agar, died within a few hours provided that DMEM agar plates had been stored in darkness for approximately 3 days after preparation. Standard conditions were developed for quantification of killing. The medium lost its fungicidal activity when exposed to visible light of wave length ∼400nm. The amount of energy required was estimated at 5.8 × 104 joules @ 550nm. Liquid DMEM conditioned by incubation over DMEM agar plates stored in darkness was fungicidal. We found that fungicidal activity was heat-stable (100°C). Dialysis tubing with MWC0 < 100 Daltons retained fungicidal activity. Neutral pH was required. Strains of Cryptococcus were uniformly sensitive, but some Candida species were resistant. Components of DMEM required for killing were pyridoxal and cystine. Micromolar amounts of iron shortened the time required for DMEM agar plates to become fungicidal when stored in the dark. Organic and inorganic compounds bearing reduced sulfur atoms at millimolar concentrations inhibited fungicidal activity. Our results point to a light-sensitive antifungal compound formed by reaction of pyridoxal with cystine possibly by Schiff base formation.

Azomethines Based on Pyridoxal-Derived Aromatic Aldehydes

The reaction of pyridoxal with 2,4-dihydroxybenzaldehyde in a hydrochloric acid solution gave 1-(5-formyl-2,4-dihydroxyphenyl)-7-hydroxy-6-methyl-1,3-dihydrofuro[3,4-c]pyridin-5-ium chloride. Treatment of the latter with sodium hydride in ethanol afforded a free aldehyde in 85% yield. A series of azomethines and imidazolidines was obtained by reacting the obtained aldehyde with various amines and diamines.

Reactions of pyridoxal with aromatic carboxylic acids in alcoholic medium

Reactions of pyridoxal with benzoic acid and its derivatives in alcoholic medium afforded alkoxyfuropyridinium salts with potential biological activity.

Reaction of pyridoxal and its azomethines with hydrophosphoryl compounds

GRAPHICAL ABSTRACT

Reaction of Pyridoxal with Hydrophosphoryl Compounds

AbstractThe products of carbonyl phosphonylation of pyridoxal with dialkylphosphinous acid, alkylphosphinic acid ethyl esters, and phosphorous acid dialkyl (or diphenyl) esters have been obtained for the first time. In some cases, the products of addition are hydrolytically unstable and stabilized by forming internal betaine structures. The reaction of pyridoxal with phosphorous acid in alcohol solutions gives alkoxyfuropyridines possessing the iminium nitrogen atom. The structure and composition of the prepared compounds have been established by 31P and 1H NMR spectroscopy, mass spectrometry (MALDI‐TOF), and X‐ray analysis.

Pyridoxal reactions with amines and aliphatic diamines

Interaction of pyridoxal (3-hydroxy-5-hydroxymethyl-2-methylisonicotinaldehyde) with amines, mono- and disubstituted diamines led to the formation of compounds having in their structure imine, imidazolidine, and pyrimidine moieties. Structure of the obtained compounds was proved by IR data, 1H NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis.

ChemInform Abstract: Reaction of Pyridoxal with Phenols: Synthesis of Novel 1‐Aryl‐Substituted Furopyridines.

AbstractThe new method is based on the acid‐catalyzed reaction of pyridoxal with polyfunctional phenols for the synthesis of potentially biologically active furopyridine derivatives.

Chemical transformations of the condensation products of pyridoxal with L-α-alanine and D-α-alanine

The kinetics and mechanism of the reactions of pyridoxal with L- and D-α-alanine were studied. Under comparable conditions, the condensation of L- and D-α-alanines with pyridoxal includes three kinetically different steps. The first fast step is addition of the amino acid to pyridoxal with formation of the corresponding amino alcohol, the second (slower) step is dehydration of the amino alcohol to give Schiff base, and the third (very slow) step is elimination of α-hydrogen atom from the L-α-amino acid fragment or decarboxylation of the D-α-amino acid fragment, followed by isomerization of the Schiff base to quinoid structure whose subsequent hydrolysis yields pyridoxamine and pyruvic acid or acetaldehyde, respectively. A scheme was proposed for chemical transformations of the pyridoxal condensation products with L- and D-α-alanines.

Pyridoxal 5′ –phosphate as photosensitizer in photo inactivation of multienzyme complexes

The reaction of pyridoxal 5′ phosphate(PLP) with fatty acid synthetase(FAS) from pigeon liver both in the presence and absence of light resulted in inactivation of overall FAS activity. Under both conditions similar kinetics of inactivation was observed for the first 8 min. NADPH showed a 60% of protection of the illuminated sample suggesting that modification of the essential residues is involved in the binding of the coenzyme. Although the PLP-treated enzyme in the dark was reactivated by subsequent dilution with the buffer but the illuminated enzyme sample was not reactivated on dilution. Spectrophotometric examination of the pyridoxal-phosphate treated fatty acid synthetase in the light and in dark suggested that the environment of PLP bound to the enzyme is altered by a nearby group resulting in appearance of a new fluorescence maxima at 445 nm when excited at 325 nm in the absence of reduction with sodium borohydride. This observation indicated that PLP and lysine of an active site of FAS formed a schiff base which has undergone an attack by a nearby nucleophilic group resulting in an irreversible and inactive enzyme-PLP complex. It appears that imidazole group of a histidine residue may be the nucleophilic agent involved in the photo-modification. These studies with pigeon liver FAS showed that lysine and histidine residues are present in enoyl –CoA reductase domain.

N,N'-ethylenebis(pyridoxylideneiminato) and N,N'-ethylenebis(pyridoxylaminato): synthesis, characterization, potentiometric, spectroscopic, and DFT studies of their vanadium(IV) and vanadium(V) complexes.

The Schiff base N,N'-ethylenebis(pyridoxylideneiminato) (H(2)pyr(2)en, 1) was synthesized by reaction of pyridoxal with ethylenediamine; reduction of H(2)pyr(2)en with NaBH(4) yielded the reduced Schiff base N,N'-ethylenebis(pyridoxylaminato) (H(2)Rpyr(2)en, 2); their crystal structures were determined by X-ray diffraction. The totally protonated forms of 1 and 2 correspond to H(6)L(4+), and all protonation constants were determined by pH-potentiometric and (1)H NMR titrations. Several vanadium(IV) and vanadium(V) complexes of these and other related ligands were prepared and characterized in solution and in the solid state. The X-ray crystal structure of [V(V)O(2)(HRpyr(2)en)] shows the metal in a distorted octahedral geometry, with the ligand coordinated through the N-amine and O-phenolato moieties, with one of the pyridine-N atoms protonated. Crystals of [(V(V)O(2))(2)(pyren)(2)].2 H(2)O were obtained from solutions containing H(2)pyr(2)en and oxovanadium(IV), where Hpyren is the "half" Schiff base of pyridoxal and ethylenediamine. The complexation of V(IV)O(2+) and V(V)O(2) (+) with H(2)pyr(2)en, H(2)Rpyr(2)en and pyridoxamine in aqueous solution were studied by pH-potentiometry, UV/Vis absorption spectrophotometry, as well as by EPR spectroscopy for the V(IV)O systems and (1)H and (51)V NMR spectroscopy for the V(V)O(2) systems. Very significant differences in the metal-binding abilities of the ligands were found. Both 1 and 2 act as tetradentate ligands. H(2)Rpyr(2)en is stable to hydrolysis and several isomers form in solution, namely cis-trans type complexes with V(IV)O, and alpha-cis- and beta-cis-type complexes with V(V)O(2). The pyridinium-N atoms of the pyridoxal rings do not take part in the coordination but are involved in acid-base reactions that affect the number, type, and relative amount of the isomers of the V(IV)O-H(2)Rpyr(2)en and V(V)O(2)-H(2)Rpyr(2)en complexes present in solution. DFT calculations were carried out and support the formation and identification of the isomers detected by EPR or NMR spectroscopy, and the strong equatorial and axial binding of the O-phenolato in V(IV)O and V(V)O(2) complexes. Moreover, the DFT calculations done for the [V(IV)O(H(2)Rpyr(2)en)] system indicate that for almost all complexes the presence of a sixth equatorial or axial H(2)O ligand leads to much more stable compounds.

Intermediate Species Absorbing in the 500-nm Region in Al(III) Catalyzed Nonenzymatic Transamination.

Course of the formation of a quinonoid species absorbing in the 500-nm region, which should serve as a model for the key intermediate in reactions catalyzed by pyridoxal phosphate enzymes, was studied in the reaction of pyridoxal, ethyl L-alaninate and Al(III) in methanol by means of UV-visible spectroscopy, chromatography with a multi-UV detector, optical rotation and 1H-NMR. The species was chromatographically separated in the form of the Al(III) chelate and its quantitative transformation to the aldimine chelate was observed. The formation of the species in the transamination reaction of pyridoxamine, ethyl pyruvate and Al(III) was also studied.

3,5-Di-tert-butyl-1,2-benzoquinone Cleaves a CC-bond in Vicinal Aminobenzyl Alcohols

Two vicinal aminobenzyl alcohols, L-threo-1-(4-methylthiophenyl)-2-amino-1,3-propanediol (IIa) and 1-phenyl-2-amino-1,3-propanediol (IIb), underwent, under mild conditions, CC-bond cleavage with 3,5-di-tert-butyl-1,2-benzoquinone (I) producing in high yields 4-methylthiobenzaldehyde (Va) and benzaldehyde (Vb), respectively, and 2-hydroxymethyl-4,6-di-tert-butylbenzoxazole (VII). Ethanolamine (VIII) under identical conditions produced benzoxazole VII. The reported reaction is a second case in which quinone I mimics reactions of pyridoxal.

ChemInform Abstract: X=Y‐ZH Systems as Potential 1,3‐Dipoles. Part 10. The Decarboxylative Route to Azomethine Ylides. Background and Relevance to Pyridoxal Decarboxylases.

AbstractThe reaction of pyridoxal (I) with α‐amino acids such as (II) in the presence of N‐phenylmaleimide (III) gives rise to two series of cycloadducts.

Micellar-catalyzed reactions for flow-injection systems : Determination of pyridoxal

The advantages of applying the solubilization and catalytic properties of aqueous micelle solutions to reactions taking place in flow-injection systems are demonstrated. The reaction of pyridoxal (a B 6 vitamin) with cyanide was investigated in both aqueous and micellar cetyltrimethylammonium bromide (CTAB) solution. Higher sensitivities and lower limits of detection were obtained for the micellar carrier, with the pseudo-first-order reaction rate increasing by a factor of two in 0.05 M CTAB relative to water carrier. Because the micellar aggregates also increase fluorescence quantum yields, use of fluorescence detection gave further signal enhancement, with the limit of detection lowered by a factor of three. Measurement of dispersion in the two systems was also investigated and compared. A new method of characterizing dispersion in flow-injection systems, based on moment analysis of exponentially modified Gaussian peak shapes, is described.

ChemInform Abstract: REACTION OF PYRIDOXAL 5′‐PHOSPHATE WITH TRIS

Kinetic and equilibrium studies are presented on the reaction of pyridoxal 5′-phosphate withTris. Upon raising thepH from 7.3 to 9.3 at 25°C, the second-order rate constant increases from 1.05 M−1 s−1 to 3.79 M−1 s−1, whereas the apparent dissociation constant varies from 2 to 8 mM. These results demonstrate the significance of this reaction whenTris buffer is used in studies of pyridoxal 5′-phosphate-dependent enzymes.

Reaction of pyridoxal 5′-phosphate with TRIS

Kinetic and equilibrium studies are presented on the reaction of pyridoxal 5′-phosphate withTris. Upon raising thepH from 7.3 to 9.3 at 25°C, the second-order rate constant increases from 1.05 M−1 s−1 to 3.79 M−1 s−1, whereas the apparent dissociation constant varies from 2 to 8 mM. These results demonstrate the significance of this reaction whenTris buffer is used in studies of pyridoxal 5′-phosphate-dependent enzymes.

The reactions of pyridoxal 5′-phosphate with the M 4 and H 4 isoenzymes of pig lactate dehydrogenase

The H 4 and M 4 isoenzymes of pig lactate dehydrogenase are both inactivated by reaction with pyridoxal 5′-phosphate. In the early stages, inactivation is largely reversible by the addition of lysine in excess, but may be made irreversible by reduction with borohydride. This indicates that modification of lysine residues probably causes the initial inactivation. Both isoenzymes also undergo a slower process of irreversible inactivation which becomes more evident with increasing concentrations of pyridoxal 5′-phosphate and higher temperature. Although coenzymes give only partial protection of enzyme activity, they nevertheless completely prevent irreversible inactivation. Neither pyruvate nor lactate alone gives any protection. With the M 4 isoenzyme, complete protection against inactivation by pyridoxal 5′-phosphate may be achieved in ternary complexes, but no conditions have been found for complete protection of the H 4 isoenzyme. In the course of irreversible inactivation of H 4 lactate dehydrogenase, complete loss of activity can be correlated with the loss of approximately two free thiol groups per subunit. Present findings with regard to the importance of temperature and reagent concentration in determining the outcome of the chemical modification appear to resolve earlier controversy.