Search for new antibacterial agents with dihydrofolate reductase-inhibitory activity among N-(R-carbamothiol)cycloalkylcarboxamides using in silico and in vitro methodology, SAR analysis to optimize the synthesis of new potential antinicrobials. Methods. Molecular docking, in vitro DHFR inhibition assay, antimicrobial evaluation, SAR analysis, statistical methods. Results. According to the results of molecular docking to the active center of dihydrofolate reductase (DHFR), namely affinity, the main types of interactions and arrangement in the active center of the enzyme, several N-(R-carbamothioyl)cycloalkylcarboxamides were selected for their inhibitory effect. Based on in vitro screening, few promising compounds with high ability to inhibit DHFR were identified. It was found, that diacylsemicarbazides are more effective inhibitors of DHFR compared to acylthioureas. The studies on antibacterial activity have revealed several promising compounds, namely N-(2-R-hydrazine-1-carbonothioyl)cycloalkanecarboxamides, as highly active antimicrobial agents against E. сoli and St. aureus (MIC 3.125-25.0 μg/ml) with high DHFR-inhibitory effect, the activity of which competes with the comparison drug "Nitrofurazone". This justifies the continuation of systematic research in this direction. Conclusions. A well-founded search among N-(R-carbamothiol)cycloalkylcarboxamides for new antibacterial agents with dihydrofolate reductase-inhibitory activity, using in silico and in vitro methodology, established relationship between the chemical structure and activity aimed at further design of new potential drug agents.

It is known that carboxyl groups bonded to aryl or hetaryl moieties play a role of the "pharmacophore" fragment in most NSAID molecules. It should be mentioned that the carboxyl group may cause the appearance of toxic effects and is characterized by unsatisfactory pharmacokinetic properties. The structural modification of the carboxyl group, including its bioisosteric replacement, is among the most widely used approaches in medicinal chemistry to improve pharmacodynamic, pharmacokinetic and technological characteristics. Aim. To develop the synthetic procedures for functional derivatives of 3-R-2,8-dioxo-7,8-dihydro-2Н-pyrrolo[1,2-а]-[1,2,4]triazino[2,3-с]quinazoline-5а(6Н)-carboxylic(-propanoic) acids, study the effect of the carboxyl group chemical modification on the LOX-inhibiting and antiradical activity as a possible mechanism of the pharmacological activity. Results and discussion. The synthesis of esters of 3-(2,8-dioxo-3-R 1-7,8-dihydro-2H-pyrrolo[1,2-a][1,2,4]triazino[2,3-c]quinazolin-5a(6H)-yl)carboxylic(propanoic) acids was conducted by esterification of the corresponding acids and tandem heterocyclization of 2-(6-R 1-2,5-dihydro-5-оxo-1,2,4-triazino-3-yl)anilines with diethyl 4-oxoheptanedioate. The synthesis of amides was conducted by aminolysis of N-acylimidazolides generated in situ. The antiradical and LOX-inhibiting activities of the compounds obtained were studied as possible mechanisms of the anti-inflammatory activity. The series of the compounds revealed the LOX-inhibiting activity that was comparable with the effect of the reference compound-nordihydroguaiaretic acid. Experimental part. The synthetic procedures were conducted according to the commonly used methods. The purity and the structure of the compounds obtained were proven by modern physicochemical methods (1 H and 13 C NMR-spectroscopy, LC-MS-spectrometry). The antiradical activity was measured by the ability to scavenge a DPPH-radical. The study of the LOX-inhibiting activity was performed using soybean LOX as an enzyme and linolenic acid as a substrate. Conclusions. The methods for the synthesis of esters and amides of 2,8-dioxo-3-R 1-7,8-dihydro-2Hpyrrolo[1,2-a][1,2,4]triazino[2,3-c]quinazolin-5a(6H)-carboxilic(propanoic) acids have been developed. The abovementioned transformations were conducted by alcoholysis of generated in situ acyl halides and aminolysis of N-acylimidazolides, respectively. The more efficient approach for the synthesis of the target esters via condensation of 2-(6-R 1-2,5-dihydro-5-oxo-1,2,4-triazino-3-yl)anilines with diethyl 4-oxoheptanedioate has been proposed. It has been found that the highest radical scavenging and LOX-inhibiting activities are characteristic for hetarylpropanoic acids that contain electron withdrawing substituents in position 3, as well as fluorine atoms in positions 11 and 12. The chemical modification of the carboxylic group in most cases results in a decrease or the loss of the activity.