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Aim. To synthesize 2-(4,6-di(pyrrolidin-1-yl)-1,3,5-triazin-2-yl)-N-(alkyl, aryl)hydrazine-1-carbothioamides and study their antiviral activity against yellow fever virus (YFV).

Results and discussion. The target 2-(4,6-di(pyrrolidin-1-yl)-1,3,5-triazin-2-yl)-N-(alkyl, aryl)hydrazine-1-carbothioamides were obtained in three-step format from cyanuric chloride in good to high yields. The carbothioamides synthesized were estimated to possess the antiviral activity against YFV. The results obtained indicate that most of the compounds studied show the inhibitory activity against YFV in concentrations ≤10 μg/mL. For the most active substances, EC₉₀ was in the range of 0.06 – 2.2 μg/mL. Good effective concentration values were accompanied by low levels of cytotoxicity resulting in excellent selectivity index values. The data obtained also indicate that the presence of an alkyl substituent in ortho-position of the N-aryl fragment is crucial for an effective inhibition of YFV growth.

Experimental part. 2-(4,6-Di(pyrrolidin-1-yl)-1,3,5-triazin-2-yl)-N-(alkyl, aryl)hydrazine-1-carbothioamides were synthesized starting from cyanuric chloride in three steps by its successive interaction with two equivalents of pyrrolidine, hydrazine and a series of alkyl-/arylisothiocyanates. The antiviral and cytotoxic activities of the target carbothioamides were studied in the Southern Research Institute (SRI, Birmingham, Alabama) by the viral cytopathic effect reduction assay and the virus yield reduction assay.

Conclusions. 2-(4,6-Di(pyrrolidin-1-yl)-1,3,5-triazin-2-yl)-N-(alkyl, aryl)hydrazine-1-carbothioamides synthesized have been proven to be a promising class of compounds for treating such a severe viral disease as yellow fever.

Aim. To provide a brief literature review regarding the structure of the human coronavirus SARS-CoV-2, the mechanism of its replication and the role of viral proteases in this process; to analyze the ability of the known antiviral agents and compounds synthesized de novo in order to bind and inhibit the coronavirus main protease using computer simulation tools.

Results and discussion. COVID-19 coronavirus has become a worldwide challenge in recent months. Taking into account the rapid spread and severity of COVID-19 among a significant part of the population there is an urgent need to develop effective medicines and appropriate treatment protocols, which, unfortunately, are not yet available. Currently, the search for molecules with an acceptable toxicity profile that are able to inhibit and/or stop coronavirus SARS-CoV-2 replication in the human body is very relevant. In this study, the virtual screening and molecular docking of both antiviral agents known and new compounds synthesized have been performed based on the structure of the main protease M^pro of SARS-CoV-2. The regularities identified during our study can be useful for searching and developing new antiviral drugs to control COVID-19 and other coronavirus infections. The analysis of the results of calculations of physicochemical characteristics of antiviral agents, as well as the determination of their binding sites with the main viral protease M^pro gives an optimistic assessment of the possibility to develop new drugs based on the structures of the known antiviral drugs or their modified analogs.

Experimental part. Based on recent studies of the crystal structure of the virus main protease M^pro in the complex with various inhibitors (Protein Data Bank http://www.rcsb.org/pdb, the structure code – 6LU7) the virtual screening and molecular docking of 100 known antiviral agents and 50 novel compounds synthesized were performed. The screening data for the in vitro antimalarial activity of the compounds synthesized were presented. The following binding and physicochemical parameters of the ligand–protein interaction for all virus main protease potential inhibitors were calculated: binding affinity score (BAS), binding energy, lipophilicity (clogP) and topological polar surface area (TPSA). The protein and ligand structures were studied using Jmol, PyMol, and Avogadro graphics software packages. The virtual screening and molecular docking, as well as the analysis of the results were performed using a LigandScout 4.4 software package. Data on the antimalarial activity of 50 compounds synthesized were obtained from the Laboratory of Microbiology, Parasitology and Hygiene of theUniversity ofAntwerp (Belgium).

Conclusions. According to the results of the virtual screening and molecular docking with protein 6LU7 it has been found that a number of the known antiviral drugs have a certain potential for their use as inhibitors of SARS-CoV-2 coronavirus main protease. Remdesivir and ritonavir substances have shown higher activity than the reference compound of the 6LU7 complex. The molecular docking of a series of compounds recently synthesized with the proven in vitro antimalarial activity has revealed that L1 – L6 compounds are promising candidates for further modification and development of new antiviral drugs to control coronavirus infection.

Received: 02.04.2020
Revised: 23.05.2020
Accepted: 29.05.2020