8-Hydroxy-5-nitroquinoline as a C-nucleophilic reagent in the reaction of C, C-coupling with quinazoline

The first example of the reaction of 5-nitro-8-hydroxyquinoline as a C-nucleophile with quinazoline is described. As a result of the reaction of C, C-coupling, a stable σ-adduct containing the drug nitroxalin on a heterocyclic carrier was obtained. The structure of the resulting adduct was confirmed by 2D 1H-13C HSQC, 1H-13C HMBC, and 1H-15N HMBC spectra

RADICAL C–H AMINATION OF CYCLIC NITRONES ENABLED BY IODINE CATALYSIS

This work was financially supported by the Russian Science Foundation, project # 20-43-01004

Redox Conversions of 5-Methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4triazolo[1,5-a]pyrimidinide l-Arginine Monohydrate as a Promising Antiviral Drug

This article presents the results of a study of electrochemical transformations in aqueous and aprotic media of 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidinide l-arginine monohydrate (1a, Triazid) obtained by electrochemical methods and ESR spectroscopy. The effect of pH on the current and the reduction potential of 1a in an aqueous Britton–Robinson buffer solution was studied. It was found that 1a is irreversibly reduced in aqueous acidic media on a glassy carbon electrode in one stage with the participation of six electrons and the formation of 5-methyl-6-amino-7-oxo-1,2,4-triazolo[1,5-a]pyrimidin. The electroreduction of 1a in DMF on a background of tetrabutylammonium salts proceeds in two stages, controlled by the kinetics of second-order reactions. In the first stage, the reduction of 1a is accompanied by protonation by the initial compound of the basic intermediate products formed in the electrode reaction (self-protonation mechanism). The second quasi-reversible stage of the electroreduction 1a corresponds to the formation of a dianion radical upon the reduction of the heterocyclic anion 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidin, which is formed upon the potentials of the first peak. The ESR spectrum of the radical dianion was recorded upon electroreduction of Triazid in the presence of Bu4NOH. The effect of the formation of ion pairs on the reversibility of the second peak of the 1a transformation is shown. A change in the rate and regioselectivity of the protonation of the dianion radical in the presence of Na+ and Li+ ions is assumed. The results of studying the electroreduction of 1a by ESR spectroscopy with a TEMPO trap make it possible to assume the simultaneous formation of both a nitroxyl radical and a radical with the spin density localized on the nitrogen at the 4 position of the six-membered ring. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This work was supported by the Russian Foundation for Basic Research (RFBR, project No. 19-29-08015 mk)

TEFLON-4 IN HIGH-DOSE EPR DOSIMETRY FOR ROUTINE MEASUREMENTS

In this work the possibility of using PTFE as a detector of dosimetric EPR-systems for control of radiation technologies is considered. A series of experimental results confirming the principal possibility of using PTFE-based detectors in high-dose dosimetry of ionizing radiation have been obtained.Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта № 20-38-90239

COMPARISON AND ANALYSIS OF EPR-SPECTRA OF TEFLON-4 AND TEFLON-40

In this paper the prospects of using Teflon-40 as a detector for dosimetric EPR systems are discussed. Experimental data shows its increased radiation resistance compared to Teflon-4.Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта № 20-38-90239

New TEMPO–Appended 2,2′-Bipyridine-Based Eu(III), Tb(III), Gd(III) and Sm(III) Complexes: Synthesis, Photophysical Studies and Testing Photoluminescence-Based Bioimaging Abilities

Linked to Alzheimer’s disease (AD), amyloids and tau-protein are known to contain a large number of cysteine (Cys) residues. In addition, certain levels of some common biogenic thiols (cysteine (Cys), homocysteine (Hcy), glutathione (GSH), etc.) in biological fluids are closely related to AD as well as other diseases. Therefore, probes with a selective interaction with the above-mentioned thiols can be used for the monitoring and visualizing changes of (bio)thiols in the biological fluids as well as in the brain of animal models of Alzheimer’s disease. In this study, new Eu(III), Tb(III), Gd(III) and Sm(III) complexes of 2,2′-bipyridine ligands containing TEMPO fragments as receptor units for (bio)thiols are reported. The presence of free radical fragments of the ligand in the complexes was proved by using the electronic paramagnetic resonance (EPR) method. Among all the complexes, the Eu(III) complex turned out to be the most promising one as luminescence- and spin-probe for the detection of biogenic thiols. The EPR and fluorescent titration methods showed the interaction of the resulting complex with free Cys and GSH in solution. To study the practical applicability of the probes for the monitoring of AD in-vivo, by using the above-mentioned Eu(III)-based probe, the staining of the brain of mice with amyloidosis and Vero cell cultures supplemented with the cysteine-enriched medium was studied as well as the fluorescence titration of Bovine Serum Albumin, BSA (as the model for the thiol moieties containing protein), was carried out. Based on the results of fluorescence titration, the formation of a non-covalent inclusion complex between the above-mentioned Eu(III) complex and BSA was suggested. © 2022 by the authors.Ministry of Education and Science of the Russian Federation, Minobrnauka, (075-15-2020-777)This work was supported by the Ministry of Science and Higher Education of the Russian Federation (Grant no.: 075-15-2020-777)

TEFLON EPR DETECTORS

A series of experimental results was obtained showing the possibility of using the domestic EPR / PTFE dosimetry system for routine dose measurements. Also was investigate signal fading electron paramagnetic resonance (EPR) in PTFE detector

Proton Activity in Nanochannels Revealed by Electron Paramagnetic Resonance of Ionizable Nitroxides: A Test of the Poisson-Boltzmann Double Layer Theory

Chemical and physical processes occurring within the nanochannels of mesoporous materials are known to be determined by both the chemical nature of the solution inside the pores/channels as well as the channel surface properties, including surface electrostatic potential. Such properties are important for numerous practical applications such as heterogeneous catalysis and chemical adsorption including chromatography. However, for solute molecules diffusing inside the pores, the surface potential is expected to be effectively screened by counter ions for the distances exceeding the Debye length. Here, we employed electron paramagnetic resonance spectroscopy of ionizable nitroxide spin probes to experimentally examine the conditions for the efficient electrostatic surface potential screening inside the nanochannels of chemically similar silica-based mesoporous molecular sieves (MMS) filled with water at ambient conditions and a moderate ionic strength of 0.1 M. Three silica MMS having average channel diameters of D = 2.3, 3.2, and 8.1 nm (C 12 MCM-41, C 16 MCM-14, and SBA-15, respectively) were chosen to investigate effects of the channel diameter at the nanoscale. The results are compared with the classical Poisson-Boltzmann (PB) double layer theory developed for diluted electrolytes and applied to a cylindrical capillary of infinite extent. While the surface electrostatic potential was effectively screened by the counter ions inside the largest channels of 8.1 nm in diameter (SBA-15), the effect of the surface electrostatic potential on local effective pH was significant for the 3.2 nm channels (C 16 MCM-14). The smaller channels of C 12 MCM-41 (2.3 nm in diameter) provided the most critical test for the PB equation that is based on a continuum electrostatic model and demonstrated its inapplicability likely due to the discrete nature of molecular systems at the nanoscale and nanoconfinement effects, leading to larger spatial heterogeneity. © 2018 American Chemical Society.*E-mail: [email protected] (E.G.K.). *E-mail: [email protected] (A.I.S.). ORCID Alex I. Smirnov: 0000-0002-0037-2555 Author Contributions The manuscript was written through contributions from all the authors. All authors have given approval to the final version of the manuscript. Funding E.G.K., L.S.M., D.O.A., D.P.T., and A.N.T. acknowledge the financial support of the Program 211 of the Government of the Russian Federation no. 02.A03.21.0006, RFBR grants 17-03-00641 and 18-29-12129mk, and the State Task from the Ministry of the Education and Science of the Russian Federation nos. 4.9514.2017/8.9 and 4.7772.2017/8.9. A.M. and A.I.S. acknowledge the financial support of the U.S. DOE Contract DE-FG02-02ER15354 (modeling of electrostatic phenomena in the nanochannels and the final preparation of the manuscript). Notes The authors declare no competing financial interest

MnO2-Mediated Oxidative Cyclization of “Formal” Schiff’s Bases: Easy Access to Diverse Naphthofuro-Annulated Triazines

A different type of MnO2-induced oxidative cyclization of dihydrotriazines has been developed. These dihydrotriazines are considered as a “formal” Schiff’s base. This method provided easy access to naphthofuro-fused triazine via the C-C/C-O oxidative coupling reaction. The reaction sequence comprised the nucleophilic addition of 2-naphthol or phenol to 1,2,4-triazine, followed by oxidative cyclization. The scope and limitations of this novel coupling reaction have been investigated. Further application of the synthesized compound has been demonstrated by synthesizing carbazole-substituted benzofuro-fused triazines. The scalability of the reaction was demonstrated at a 40 mmol load. The mechanistic study strongly suggests that this reaction proceeds through the formation of an O-coordinated manganese complex

EPR SPECTROMETRY FOR FOOD RESEARCH

In this work, a qualitative analysis is carried out by EPR methods in the middle region. Processes occurring in a number of plant foods when exposed to various doses. Using the EPR method, it was found that the starting materials contain a small amount of steam, magnetic centers of free radicals