Egor A. Nikiforov

An original, transition metal-free, two-step synthetic strategy based on sequential S_N ^H and S_N ^Ar reactions, namely C–H functionalization of nonaromatic 2H-imidazole 1-oxide with pentafluorophenyl lithium followed by aromatic fluorine substitution with arylthioles, was proposed. A series of new arylthio-tetrafluorobenzene-imidazole triad multifunctional compounds were prepared in good yields of 62–94%. The in silico study of the synthesized triads toward biotargets associated with endothelial dysfunction (PDE5a); cancer (EGFR, CDK2); and SARS-CoV-2 viral infection (M^pro) revealed that biotarget binding selectivity was highly sensitive to the positioning of substituents on the aromatic ring. The synthesized triads could be considered as perspective lead compounds in the design of agents for pharmaceutical applications. Received: 04 September 2025 Accepted after revision: 12 November 2025 Article published online: 09 December 2025 © 2025. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

The aim. To study the acute toxicity, endothelial- and cardioprotective properties of phenolic and thiophenolic derivatives of 2H-imidazoles.Materials and methods. The study was performed on white laboratory female BALB/c mice (n=57) and male C57Bl/6 mice (n=66). Acute toxicity was assessed according to the interstate standard GOST 32644-2014 with histological evaluation of internal organs. Endothelial dysfunction was modeled by 7-day intraperitoneal administration of N-nitro-L-arginine methyl ester (L-NAME). The studied small molecules were administered intragastrically using a probe. To assess the endothelial protective effect, the levels of systolic and diastolic blood pressure were evaluated, as well as the coefficient of endothelial dysfunction; for the cardioprotective effect, the results of stress tests on the myocardium were evaluated.Results. The study of acute toxicity of the studied small molecules allowed us to classify them as class 4 and 5. The administration of compounds 1(a–d) and 2(a–c) to mice at a dose equal to 1/10 of LD50 led to changes in blood pressure and restoration of the dynamics of pharmacological tests in response to the administration of acetylcholine and sodium nitroprusside. Molecules 1b and 2c showed statistically significant endothelial protective activity in 3 doses (1/10, 1/50 and 1/100 of LD50). Also, these hit compounds demonstrated cardioprotective effects, recorded by the restoration of the functional capabilities of the myocardium in response to load and in the adrenoreactivity test, and to a lesser extent, during resistance exercise.Conclusion. The studied compounds have low toxicity and have endothelial- and cardioprotective effects. This study may contribute to the formation of an idea about further directions in the study of the pharmacological activity of these molecules from the group of phenolic and thiophenolic derivatives of 2H-imidazoles.

Разработка новых фармакологических веществ для коррекции эндотелиальной дисфункции (ЭД) является перспективным направлением в фармакологии. В данном исследовании оценены острая токсичность, эндотелио- и кардиопротекторные свойства оригинальных малых молекул — 5-(пиррол-2-ил)- и 5-морфолинозамещенных производных 2H-имидазола. Фармакологическую активность исследовали на модели L-NAME (N-Nitroarginine Methyl Ester) индуцированной ЭД, кардиопротекторные свойства соединений оценивали на мышах путем проведения нагрузочных проб in vivo. Изучение острой токсичности исследуемых малых молекул позволило отнести их к 4 и 5 классу токсичности, соответственно. На модели L-NAME-индуцированной ЭД исследовали изучаемые соединения и эндотелиопротекторные свойства. При введении соединений в дозе 1/10 от ЛД50 систолическое АД в среднем снижалось на 17,3 %, диастолическое АД — на 16,5 % и коэффициент ЭД — в среднем на 49,4 % (p ≤ 0,05 для соединений 2-4). При введении веществ 2-4 в дозе 1/50 от ЛД50 систолическое АД в среднем уменьшалось на 18,3 %, диастолическое АД — на 20 %, а коэффициент ЭД — на 55,1 % (p ≤ 0,05). В группе животных, получавших соединения в дозе 1/100 от ЛД50, отмечали снижение уровня систолического АД на 13,7 %, диастолического АД — на 7,1 % (p ≥ 0,05), коэффициента ЭД — на 39,8 % (p ≤ 0,05 для соединений 2 и 3). Исследуемые соединения оказывали кардиопротекторный эффект в пробе с нагрузкой объемом и в пробе на адренореактивность, снижая уровень давления в левом желудочке. В пробе с нагрузкой давление в левом желудочке животных, получавших вещества в дозе 1/10 от ЛД50, в среднем снижалось на 26,3 %, в группе 1/50 от ЛД50 — на 19,3 %, в группе 1/100 от ЛД50 — на 18,1 %, по сравнению с группой L-NAME (p ≤ 0,05). При проведении пробы на адренореактивность показатель уровень давления в левом желудочке в среднем уменьшался в группе 1/10 от ЛД50 на 20,7 %, в группе 1/50 от ЛД50 — на 16,4 %, в группе 1/100 от ЛД50 — на 17,3 %, по сравнению с группой L-NAME (p ≤ 0,05).

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 (S_N^H) in non-aromatic azaheterocyclic substrates via the “addition-elimination” (S_N^H 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.

The strategy of the nucleophilic substitution of hydrogen (S_N^H) was first applied for the metal-free C-H/C-H coupling reactions of 4H-imidazole 3-oxides with indoles. As a result, a series of novel bifunctional azaheterocyclic derivatives were obtained in yields up to 95%. In silico experiments on the molecular docking were performed to evaluate the binding possibility of the synthesized small azaheterocyclic molecules to the selected biotargets (BACE1, BChE, CK1δ, AChE) associated with the pathogenesis of neurodegenerative diseases. To assess the cytotoxicity for the synthesized compounds, a series of in vitro experiments were also carried out on healthy human embryo kidney cells (HEK-293). The leading compound bearing both 5-phenyl-4H-imidazole and 1-methyl-1H-indole moieties was defined as the prospective molecule possessing the lowest cytotoxicity (IC₅₀ > 300 µM on HEK-293) and the highest binding energy in the protein–ligand complex (AChE, −13.57 kcal/mol). The developed compounds could be of particular interest in medicinal chemistry, particularly in the targeted design of small-molecule candidates for the treatment of neurodegenerative disorders.

The synthesis of inhibitors for oxidative stress-associated destructive processes based on 2H-imidazole-derived phenolic compounds affording the bifunctional 2H-imidazole-derived phenolic compounds in good-to-excellent yields was reported. In particular, a series of bifunctional organic molecules of the 5-aryl-2H-imidazole family of various architectures bearing both electron-donating and electron-withdrawing substituents in the aryl fragment along with the different arrangements of the hydroxy groups in the polyphenol moiety, namely derivatives of phloroglucinol, pyrogallol, hydroxyquinol, including previously unknown water-soluble molecules, were studied. The structural and antioxidant properties of these bifunctional 5-aryl-2H-imidazoles were comprehensively studied. The redox transformations of the synthesized compounds were carried out. The integrated approach based on single and mixed mechanisms of antioxidant action, namely the AOC, ARC, Folin, and DPPH assays, were applied to estimate antioxidant activities. The relationship “structure-antioxidant properties” was established for each of the antioxidant action mechanisms. The conjugation effect was shown to result in a decrease in the mobility of the hydrogen atom, thus complicating the process of electron transfer in nearly all cases. On the contrary, the conjugation in imidazolyl substituted phloroglucinols was found to enhance their activity through the hydrogen transfer mechanism. Imidazole-derived polyphenolic compounds bearing the most electron-withdrawing functionality, namely the nitro group, were established to possess the higher values for both antioxidant and antiradical capacities. It was demonstrated that in the case of phloroglucinol derivatives, the conjugation effect resulted in a significant increase in the antiradical capacity (ARC) for a whole family of the considered 2H-imidazole-derived phenolic compounds in comparison with the corresponding unsubstituted phenols. Particularly, conjugation of the polyphenolic subunit with 2,2-dimethyl-5-(4-nitrophenyl)-2H-imidazol-4-yl fragment was shown to increase ARC from 2.26 to 5.16 (10⁴ mol-eq/L). This means that the considered family of compounds is capable of exhibiting an antioxidant activity via transferring a hydrogen atom, exceeding the activity of known natural polyphenolic compounds.