Russian Chemical Bulletin最新文献

Microwave-assisted reactions of 10-chlorotetrahydrobenzo[b][1,6]naphthyridines with N-, S-, and C-nucleophiles resulted in the introduction of various structural moieties in position 10 to give new tetrahydrobenzo[b][1,6]naphthyridine derivatives. Substituted 10-phenyl tetrahydrobenzo[b][1,6]naphthyridines were modified at the nitrogen atom of the tetrahydropyridine moiety using activated alkynes. The esterase profile and the antioxidant activity of the obtained compounds were studied. A compound active towards acetylcholinesterase (IC₅₀ = 15.0±0.9 µmol L⁻¹) and a number of compounds selectively inhibiting butyrylcholinesterase (IC₅₀ of up to 17.5±1.4 µmol L⁻¹) were identified. Compounds with a moderate antioxidant activity in ABTS and FRAP assays were found.

The comparative analysis of the calculated and experimental ¹⁹⁵Pt NMR chemical shifts for a wide range of model platinum complexes shows that the density functional theory well reproduces the experimental data. The ¹⁹⁵Pt NMR chemical shifts can be calculated with high accuracy within the fully relativisitic four-component matrix Dirac—Kohn—Sham formalism (4c-mDKS) (R² = 0.998, RMSE = 52 ppm, and MDR = 0.9%). The PBE0/{6–31+G(d); Pt(SDD)} approximation may be sufficient for geometry optimization of the complexes. However, the presence of heavy atoms directly bound to platinum requires consideration of their scalar relativistic effects on the geometry at the optimization stage. The problems of shielding calculation for the common [PtCl₆]²⁻ reference can be minimized performing an empirical linear correction. At the same time, if the pseudorelativistic approximation based on application of all-electron relativistically contracted basis sets (NMR-DKH) is used, the accuracy of estimation is several-fold worse (R² = 0.968, RMSE = 200 ppm, and MDR = 2.9%), even with linear correction for reducing large systematic errors.

Water-soluble hybrid nanocomposites consisting of zero-valent bismuth nanoparticles with a size of 8.0–22.0 nm have been synthesized for the first time using the stabilizing ability of natural polysaccharide arabinogalactan. The structure of the nanocomposites was characterized by a complex of physicochemical methods: phase X-ray diffraction (XRD), transmission electron microscopy, and dynamic light scattering. Ecotoxicity and antimicrobial activity of the prepared bismuth-containing nanocomposites were studied using available biological test systems of various types. The latter has a pronounced dose-dependent character.

The rate constants of the reactions of β-alanyl-β-alanine with 2,4-dinitro- and 2,4,6-trinitrophenyl benzoates in a water—1,4-dioxane system under polythermal conditions were determined in the present kinetic study. The rate constants vary in a range of 0.7–30.58 L mol⁻¹ s⁻¹. The found activation parameters of dipeptide N-acylation are comparable (within the determination error) with the kinetic characteristics of the reactions of the same family. A twofold increase in the water content in the water—1,4-dioxane solvent results in a 2–2.5 times increase in the average value of the rate constant. A comparison of the kinetic parameters of the reactions under study with the earlier obtained results for reactions involving other dipeptides revealed the following order of the reactivity of dipeptides: β-Ala-β-Ala > Gly-Gly > Ala-Val > Gly-Leu > Tyr-Pro. This sequence is consistent with the order of decreasing basicity of these dipeptides and indicates a substantial influence of the basicity on the reactivity of dipeptides. Based on the results of quantum chemical calculations of the potential energy surfaces of the model reaction of β-alanyl-β-alanine with phenyl acetate in the gas phase and under the conditions of hydration of the amino group of dipeptide by a water molecule, a conclusion can be made that the bimolecular concerted nucleophilic substitution on the carbonyl reaction center is possible.

An effect of the substituents in pyridinium ylides on oxidative 1,3-dipolar cycloaddition to nitrostilbenes, the scope and limitations of this transformation were studied. This reaction depending of the nature of the substituents gave either 1,2-diarylindolizines or 3,4-diarylisoxazoline N-oxides.

A series of dispiro-fused imidazothiazolotriazine-pyrrolidine-oxindoles with two ester groups in the pyrrolidine ring was synthesized by the [3+2] cycloaddition of azomethine ylides to dipolarophiles, functionalized imidazothiazolotriazines bearing tetrasubstituted double bonds. The treatment of the synthesized compounds with bases resulted in the selective hydrolysis of one of the two ester groups thus providing possibility for the target modification of the compound functionality and synthesis of the corresponding carboxylic acids and then amides in good yields.

Reaction of readily available 1-aryl-1-chlorocyclopropanes with alcohols in the KOH—DMSO system at 80–100 °C affords corresponding 1-alkoxy-2-arylcyclopropanes in up to 92% yield. The procedure is simple to implement, provides high stereoselectivity, and in most cases allows one to obtain products with trans-arrangement of the alkoxy group and aryl fragment. The results obtained suggest that isomerization of 1-alkoxy-2-arylcyclopropanes can occur under the strongly basic conditions used due to inversion of the configuration of the cyclopropane carbon atom located at the aromatic substituent.

The regioselectivity of the cyclization of 7-[(E)-2-(dimethylamino)vinyl]pyrazolo-[1,5-a]pyrimidine-6-carbonitriles was studied in the reactions with hydrazine hydrate. Depending on the conditions, the reaction in acetic acid or DMF affords either linear 6-(1H-pyrazol-5-yl)pyrazolo[1,5-a]pyrimidin-7-amines via the ANRORC rearrangement or fused 6-iminopyrazolo[1,5-a]pyrido[3,4-e]pyrimidin-7(6H)-amines. The preliminary in vitro screening of the antibacterial activity of the synthesized compounds was performed against E. coli and S. aureus.

Inorganic nano- and microparticles offer great opportunities for use as microfertilizers and carriers of both high- and low-molecular-weight compounds. This review examines the principal types of inorganic nano- and microparticles, namely, metal and metal oxide nanoparticles, particles based on silicon compounds and insoluble calcium salts, as well as the methods for their preparation and their potential applications in plant growing.

Composites based on physically cross-linked polyvinyl alcohol (PVA) alcogels containing electrically conductive polypyrrole (PPy) were obtained. For the first time, polyvinyl alcohol gels (antifreeze-PVA) were formed by gelation of a PVA solution in aqueous ethanol under conditions that prevented freezing of the gel-like composition. During gelation, oxidative polymerization of pyrrole took place. It was shown that addition of ethanol into the system increases the PPy content in anti-freezing PVA gel compared to PVA cryogel (cryo-PVA). The resulting dried composites were characterized by scanning electron microscopy, energy dispersive X-ray microanalysis, and IR spectroscopy. The conductivity of antifreeze-PVA—PPy composites was an order of magnitude higher than that of cryo-PVA—PPy; with the increase in the PPy content, the current–voltage characteristics acquired a non-Ohmic nature.