An Efficient Synthesis of 3H‐1,5‐Benzodiazepine Derivatives Catalyzed by Heteropolyacids as a Heterogeneous Recyclable Catalyst

3H‐1,5‐benzodiazepines were synthesized by the condensation of o‐phenylendiamine and various 1,3‐diketones in the presence of various heteropolyacid (HPA) catalysts under mild conditions in very good yields and with high selectivity.     

BF3·SiO2: an efficient alternative for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes

Silica-supported boron trifluoride (BF₃·SiO₂) is an efficient, readily available, and reusable catalyst for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes by condensation of 2-naphthol and aldehydes. This reaction under heating or sonication conditions is very simple, affording good to excellent yields of products.     

Use of volatile organic solvents in headspace liquid‐phase microextraction by direct cooling of the organic drop using a simple cooling capsule

A low‐cost and simple cooling‐assisted headspace liquid‐phase microextraction device for the extraction and determination of 2,6,6‐trimethyl‐1,3 cyclohexadiene‐1‐carboxaldehyde (safranal) in Saffron samples, using volatile organic solvents, was fabricated and evaluated. The main part of the cooling‐assisted headspace liquid‐phase microextraction system was a cooling capsule, with a Teflon microcup to hold the extracting organic solvent, which is able to directly cool down the extraction phase while the sample matrix is simultaneously heated. Different experimental factors such as type of organic extraction solvent, sample temperature, extraction solvent temperature, and extraction time were optimized. The optimal conditions were obtained as: extraction solvent, methanol (10 μL); extraction temperature, 60°C; extraction solvent temperature, 0°C; and extraction time, 20 min. Good linearity of the calibration curve (R² = 0.995) was obtained in the concentration range of 0.01–50.0 μg/mL. The limit of detection was 0.001 μg/mL. The relative standard deviation for 1.0 μg/mL of safranal was 10.7% (n = 6). The proposed cooling‐assisted headspace liquid‐phase microextraction device was coupled (off‐line) to high‐performance liquid chromatography and used for the determination of safranal in Saffron samples. Reasonable agreement was observed between the results of the cooling‐assisted headspace liquid‐phase microextraction high‐performance liquid chromatography method and those obtained by a validated ultrasound‐assisted solvent extraction procedure.     

Synthesis,structure, and electrochemistry of <Emphasis Type="Italic">trans</Emphasis>-[Co<Superscript>III</Superscript>{(BA)<Subscript>2</Subscript>pn}(L)<Subscript>2</Subscript>]ClO<Subscript>4</Subscript> complexes

The structure, spectroscopic, and electrochemical properties of [Co{(BA)₂pn}(L)₂]ClO₄ complexes, where (BA)₂pn = N,N′-bis(benzoylacetone)-1,3-propylenediimine dianion and the two ancillary ligands (L) are pyridine, py (1), and 4-methylpyridine, 4-Mepy (2), have been investigated. These complexes have been characterized by elemental analyses, IR, UV–Vis and ¹H-NMR spectroscopy. The crystal structure of [Co{(BA)₂pn}(py)₂]ClO₄ (1) has been determined by X-ray diffraction. The coordination geometry around cobalt(III) is best described as a distorted octahedron. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial N(py)–cobalt bonds. This process becomes quasi-reversible upon the addition of excess py ligands. The second reduction step of Co^II/I shows reversible behavior and is not influenced by the nature of the axial ligands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Characterization of hydrocortisone biometabolites and 18S rRNA gene in Chlamydomonas reinhardtii cultures

A unicellular microalga, Chlamydomonas reinhardtii, was isolated from rice paddy-field soil and water samples and used in the biotransformation of hydrocortisone (1). This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25 degrees C for 14 days of incubation. The products obtained were chromatographically purified and characterized using spectroscopic methods. 11b,17 beta-Dihydroxyandrost-4-en-3-one (2), 11 beta-hydroxyandrost-4-en-3,17-dione (3), 11 beta,17 alpha,20 beta,21-tetrahydroxypregn-4-en-3-one (4) and prednisolone (5) were the main products of the bioconversion. The observed bioreaction features were the side chain degradation of the substrate to give compounds 2 and 3 and the 20-ketone reduction and 1,2-dehydrogenation affording compounds 4 and 5, respectively. A time course study showed the accumulation of product 2 from the second day of the fermentation and of compounds 3, 4 and 5 from the third day. All the metabolites reached their maximum concentration in seven days. Microalgal 18S rRNA gene was also amplified by PCR. PCR products were sequenced to confirm their authenticity as 18S rRNA gene of microalgae. The result of PCR blasted with other sequenced microalgae in NCBI showed 100% homology to the 18S small subunit rRNA of two Chlamydomonas reinhardtii spp.     

Modification of carbonic anhydrase II with acetaldehyde, the first metabolite of ethanol, leads to decreased enzyme activity

Background

Bacillus thuringiensis Cry1Aa insecticidal protein is the most active known B. thuringiensis toxin against the forest insect pest Lymantria dispar (gypsy moth), unfortunately it is also highly toxic against the non-target insect Bombyx mori (silk worm).

Results

Surface exposed hydrophobic residues over domains II and III were targeted for site-directed mutagenesis. Substitution of a phenylalanine residue (F328) by alanine reduced binding to the Bombyx mori cadherin by 23-fold, reduced biological activity against B. mori by 4-fold, while retaining activity against Lymantria dispar.

Conclusion

The results identify a novel receptor-binding epitope and demonstrate that virtual elimination of binding to cadherin BR-175 does not completely remove toxicity in the case of B. mori.     

Toric degenerations of flag varieties from matching field tableaux

We present families of tableaux which interpolate between the classical semi-standard Young tableaux and matching field tableaux. Algebraically, this corresponds to SAGBI bases of Plücker algebras. We show that each such family of tableaux leads to a toric ideal, that can be realized as initial of the Plücker ideal, hence a toric degeneration for the flag variety.     

Polybenzimidazole‐decorated carbon nanotube: A high‐performance proton conductor

Interaction between negatively charged Nafion^® and a positively charged polybenzimidazole‐decorated carbon nanotube leads to the formation of an ionic complex with high charge density for proton conduction, which can lead to an improvement in transport properties. Here we investigate the high‐temperature and low‐humidity proton conductivity of this nanocomposite membrane as a potential membrane for fuel cell applications.

     

Study on the interaction between dinaphthosulfide-substituted macrocyclic diamides and some metal ions: experimental measurements vs. quantum mechanical calculations

Complexation properties of dinaphthosulfide-substituted macrocyclic diamides 1 and 2 with some metal cations that have been obtained by conductometric method are described with quantum mechanics calculations. To do this, the most stable structures of ligands, Hg²⁺-ligand complexes, ligand-MeOH and ClO₄ ^?–MeOH are optimized at HF/Lanl2dz level of theory and the most important interactions are analyzed by atoms in molecules (AIM) theory. These calculations predict the existence of strong interaction between Hg²⁺ cation and ligands 1 and 2, particularly, S–Hg²⁺ interaction. The different conductometric behaviors of complexation of ligands 1 and 2 with metal ions are interpreted on the basis of the calculated intramolecular hydrogen bonds in ligands and intermolecular hydrogen bonds between ligands and methanol as a solvent and perchlorate as a counter ion. In addition, binding energies between Hg²⁺ and ligands are also calculated by HF/Lanl2dz level of theory. Results show that all theoretical predictions are in line agreement with the experimental data.     

Shape control of nickel selenides synthesized by a simple hydrothermal reduction process

Nickel selenide (NiSe) nanoparticles were prepared from the reaction of a SeCl₄ aqueous solution with a NiCl₂·6H₂O aqueous solution in the presence of polyvinyl alcohol (PVA) as a capping agent and hydrazine hydrate (N₂H₄·H₂O) as a reductant through a hydrothermal method. The size, morphology, chemical composition and purity of these nanoparticles depend on the capping agent, reductant, reaction temperature and time.