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In this work, comprehensive studies of 2,4-dinitroanisole (2,4DNAN) were carried out using powder thermorentgenography of the internal standard. The time of the complete polymorphic transition in the solid phase β→α in 2,4DNAN under various combinations of conditions has been determined. It has been established that, regardless of the season of manufacture of the substance, when it is stored for 8–9 months, with a change in ambient temperature from minus 30 °C to plus 30 °C, a complete polymorphic transition β→α occurs. When stored in conditions below minus 5 °C, polymorphic transition does not occur. When stored in conditions above plus 30 °C in a closed container, polymorphic transition occurs within 3 weeks. The polymorphic transition is accompanied by a decrease in density by 1.3%–1.5% and an increase in melting temperature by 10–12 °C, depending on the degree of purity of the starting substance. The activation energy of the molecular rearrangement was 68–70 kJ/mol (16.5 ± 3 kcal/mol). The mechanism of polymorphic transition has been evaluated, which is presumably based on internal homodiffusion and energy transfer to the surface of the mass of powder particles and the product. The average activation energy of the polymorphic transition process was 110 ± 6.2 kJ/mol (26.2 kcal/mol). In an open container, reactions proceed by a homogeneous mechanism, and in a closed container by a heterogeneous mechanism involving the gas phase.

Background. The COVID-19 pandemic, caused by the SARS-CoV-2 coronavirus, originated in Wuhan, China, has claimed millions of lives around the world. In this regard, the search for effective drugs, including the repurposing of existing ones, has become an urgent task. A promising treatment strategy appears to be drug disruption of viral reproduction. RNA-dependent RNA polymerase (RdRp) is the central subunit of the RNA synthesis process for all positive-strand RNA viruses and is therefore an attractive target for antiviral inhibitors.The aim of this work is an experimental study of the antiviral activity of various drugs based on 6-fluoro-3-hydroxy-2-pyrazinecarboxamide (Favipiravir) in vitro and in vivo against the SARS-CoV-2 coronavirus (COVID-19).Material and methods. The experiments were carried out on a permanent culture of African green monkey kidney cells — Vero Cl008. The effectiveness of the drugs was assessed by suppressing the reproduction of the virus in vitro. Biological activity was assessed by titration of the virus-containing suspension in Vero Cl008 cell culture by the formation of negative colonies. Syrian golden hamsters orally infected with the SARS-CoV-2 virus, variant B, were used in the study. The effectiveness of the drug was assessed by the coefficient of therapeutic action.Results. The results of the study revealed that the compounds FP-1 and Avifavir in the concentration range of 100–400 µg/ml almost completely suppress the reproduction of the SARS-CoV-2 virus; the CTI index for the drug FP-1 was 4, for Avifavir it was 2. The ED₅₀ value for FP-1 was 26 µg/ml, for Avifavir it was 36 µg/ml. Preparations T-705 and Coronavir revealed antiviral activity only at extremely high concentrations. The CTI was 1. During the study on Syrian golden hamsters orally infected with the SARS-CoV-2 virus, variant B, at a dose of 5×105 PFU, it was shown that the use of Avifavir and FP-1 has a high protective efficacy, while Coronavir and T-705 cause a moderate suppression of virus reproduction in the target organ. According to the complex of clinical-virological, biochemical, and hematological indicators, the disease severity index (DSI) and the therapeutic index (TI) were calculated. For the drug Avifavir, the DSI was 0.269; the TI was 71.3% with a probability of 99.9%.Conclusion. Of the studied compounds, Avifavir and FP-1 showed the highest antiviral activity.

A series of 2,4-disubstituted pyrrolo[2,1-f][1,2,4]triazines containing both aryl and thienyl substituents were synthesized by exploiting the 1,3-cycloaddition reaction of N(1)-ethyl-1,2,4-triazinium tetrafluoroborates with dimethyl acetylenedicarboxylate. The antiviral activity of the synthesized compounds against influenza virus strain A/Puerto Rico/8/34 (H1N1) was studied in experiments on Madin-Darby canine kidney (MDCK) cell culture. Among the pyrrolo[2,1-f][1,2,4]triazine derivatives, compounds with low toxicity and high antiviral activity were identified. Dimethyl 4-(4-methoxyphenyl)-7-methyl-2-p-tolylpyrrolo[2,1-f][1,2,4]triazine-5,6-dicarboxylate was found to demonstrate the best antiviral activity (IC50 4 µg/mL and selectivity index 188). Based on the results of in vitro tests and molecular docking studies performed, a plausible mechanism of action for these compounds was suggested to involve inhibition of neuraminidase.

A synthetic strategy based on reactions of cyclic imine oxides, namely 2H-imidazole 1-oxides, with thiophenols mediated by acetyl chloride was successfully applied as a convenient tool to obtain a series of novel azaheterocyclic molecules, including water-soluble hydrochloride forms. Optimized reaction conditions found herein for the nucleophilic substitution of hydrogen (SNH) in non-aromatic azaheterocyclic substrates via the “addition-elimination” (SNH AE) scheme enabled 15 arylthiolated 2H-imidazoles to be prepared in yields of up to 90%. The developed methodology discloses an original synthetic way to obtain numerous azaheterocyclic molecules, which are of interest in the field of medicinal chemistry and materials science.

Two series of novel [1,2,4]triazolo[4,3-c]- and [1,2,4]triazolo[1,5-c]quinazoline fluorophores with 4′-amino[1,1′]-biphenyl residue at position 5 have been prepared via Pd-catalyzed cross-coupling Suzuki–Miyaura reactions. The treatment of 2-(4-bromophenyl)-4-hydrazinoquinazoline with orthoesters in solvent-free conditions or in absolute ethanol leads to the formation of [4,3-c]-annulated triazoloquinazolines, whereas [1,5-c] isomers are formed in acidic media as a result of Dimroth rearrangement. A 1D-NMR and 2D-NMR spectroscopy, as well as a single-crystal X-ray diffraction analysis, unambiguously confirmed the annelation type and determined the molecular structure of p-bromophenyl intermediates and target products. Photophysical properties of the target compounds were investigated in two solvents and in the solid state and compared with those of related 3-aryl-substituted [1,2,4]triazolo[4,3-c]quinazolines. The exclusion of the aryl fragment from the triazole ring has been revealed to improve fluorescence quantum yield in solution. Most of the synthesized structures show moderate to high quantum yields in solution. Additionally, the effect of solvent polarity on the absorption and emission spectra of fluorophores has been studied, and considerable fluorosolvatochromism has been stated. Moreover, electrochemical investigation and DFT calculations have been performed; their results are consistent with the experimental observation.

Treatment of recurrent oropharyngeal candidiasis (OPC) in HIV-infected patients is a serious clinical problem due to the emergence of resistant Candida strains, the risk of invasive disease, and high economic costs, which warrants the need for new treatment regimens. Aim. To improve the treatment regimen of OPC in the later stages of HIV infection by combining the complex herbal medicinal product Tonsilgon N with fluconazole and evaluate the effectiveness of this combination. Materials and methods. A comparative randomized clinical study included 65 patients divided into observation and comparison groups, receiving fluconazole plus Tonsilgon H and fluconazole monotherapy, respectively, for 7 days. On days 1 and 8, the severity of OPC clinical signs was assessed using a visual analog scale. The secretory immunoglobulin A in saliva was measured as a criterion for changing the level of local mucosal protection of the oral cavity and pharynx. Conclusion. This treatment regimen for oropharyngeal candidiasis in patients with HIV infection in the later stages of the disease (IVBIVC) with fluconazole and Tonsilgon N is effective, which is confirmed by a significantly more pronounced regression of clinical signs (pMU0.01), as well as an increase in the level of secretory immunoglobulin A in the oral fluid (from 0.620.33 g/L to 0.810.18 g/L; p0.05).

[1,2,5]Oxadiazolo[3,4-b]pyrazines are of great interest due to their promising photophysical and electrochemical properties, as well their potential use in a wide range of electronic devices. Herein, we report on the preparation of the unexpected product derived from the interaction of 2′-([1,2,5]oxadiazolo[3,4-b]pyrazin-5-yl)-N,N-diphenyl-[1,1′-biphenyl]-4-amine with 2-cyanoacetic acid under basic conditions. The resulting product was characterized using 1H and 13C NMR spectra, high resolution mass spectrometry, Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction analyses. Furthermore, its photophysical and electrochemical properties were studied using cyclic voltammetry, UV–Vis, and emission spectroscopy. The experimental results have been further rationalized through theoretical DFT calculations.

We investigated the inhibitory activities of novel 9-phosphoryl-9,10-dihydroacridines and 9-phosphorylacridines against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and carboxylesterase (CES). We also studied the abilities of the new compounds to interfere with the self-aggregation of β-amyloid (Aβ42) in the thioflavin test as well as their antioxidant activities in the ABTS and FRAP assays. We used molecular docking, molecular dynamics simulations, and quantum-chemical calculations to explain experimental results. All new compounds weakly inhibited AChE and off-target CES. Dihydroacridines with aryl substituents in the phosphoryl moiety inhibited BChE; the most active were the dibenzyloxy derivative 1d and its diphenethyl bioisostere 1e (IC50 = 2.90 ± 0.23 µM and 3.22 ± 0.25 µM, respectively). Only one acridine, 2d, an analog of dihydroacridine, 1d, was an effective BChE inhibitor (IC50 = 6.90 ± 0.55 μM), consistent with docking results. Dihydroacridines inhibited Aβ42 self-aggregation; 1d and 1e were the most active (58.9% ± 4.7% and 46.9% ± 4.2%, respectively). All dihydroacridines 1 demonstrated high ABTS•+-scavenging and iron-reducing activities comparable to Trolox, but acridines 2 were almost inactive. Observed features were well explained by quantum-chemical calculations. ADMET parameters calculated for all compounds predicted favorable intestinal absorption, good blood–brain barrier permeability, and low cardiac toxicity. Overall, the best results were obtained for two dihydroacridine derivatives 1d and 1e with dibenzyloxy and diphenethyl substituents in the phosphoryl moiety. These compounds displayed high inhibition of BChE activity and Aβ42 self-aggregation, high antioxidant activity, and favorable predicted ADMET profiles. Therefore, we consider 1d and 1e as lead compounds for further in-depth studies as potential anti-AD preparations.

A series of novel [1,2,4]triazolo[1,5-b][1,2,4,5]tetrazines has been synthesized through oxidation reaction of the corresponding 3,6-disubstituted 1,2,4,5-tetrazines bearing amidine fragments. It is shown that the heterocyclic systems obtained can be modified easily at C(3) position in the reactions with aliphatic alcohols and amines. Also, the reactivity of [1,2,4]triazolo[1,5-b][1,2,4,5]tetrazines towards CH-active compounds has been studied. The obtained triazolo[1,5-b]annulated 1,2,4,5-tetrazines proved to be active in micromolar concentrations in vitro against filamentous anthropophilic and zooanthropophilic dermatophyte fungi (Trichophyton, Microsporum and Epidermofiton), which cause skin and its appendages (hair, nails) diseases.