Novel monoterpene-based hydroxamic acids of two structural types were synthesized for the first time. The first type consisted of compounds with a hydroxamate group directly bound to acyclic, monocyclic and bicyclic monoterpene scaffolds. The second type included hydroxamic acids connected with the monoterpene moiety through aliphatic (hexa/heptamethylene) or aromatic linkers. An in vitro analysis of biological activity demonstrated that some of these molecules had powerful HDAC6 inhibitory activity, with the presence of a linker area in the structure of compounds playing a key role. In particular, it was found that hydroxamic acids containing a hexa- and heptamethylene linker and (-)-perill fragment in the Cap group exhibit excellent inhibitory activity against HDAC6 with IC₅₀ in the submicromolar range from 0.56 ± 0.01 µM to 0.74 ± 0.02 µM. The results of the study of antiradical activity demonstrated the presence of moderate ability for some hydroxamic acids to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2ROO^• radicals. The correlation coefficient between the DPPH radical scavenging activity and oxygen radical absorbance capacity (ORAC) value was R² = 0.8400. In addition, compounds with an aromatic linker based on para-substituted cinnamic acids, having a monocyclic para-menthene skeleton as a Cap group, 35a, 38a, 35b and 38b, demonstrated a significant ability to suppress the aggregation of the pathological β-amyloid peptide 1-42. The 35a lead compound with a promising profile of biological activity, discovered in the in vitro experiments, demonstrated neuroprotective effects on in vivo models of Alzheimer’s disease using 5xFAD transgenic mice. Together, the results obtained demonstrate a potential strategy for the use of monoterpene-derived hydroxamic acids for treatment of various aspects of Alzheimer’s disease.

Background. Antibiotic resistance of bacteria is a serious concern for modern medicine. The search for new compounds with a pronounced antibacterial effect is an urgent task of pharmaceutical chemistry. The aim of the study was to assess nfluence of the structure of benzimidazole and its derivatives the ability to inhibit the growth of gram-positive bacteria Bacillus subtilis. Materials and methods. Antibacterial activity of diazaheterocycles was evaluated by the method of serial dilutions. Сoncentrations from 0,06 to 1000 µg/l were used. Тhe minimum inhibitory concentration (MIC) of benzimidazole derivatives against Bacillus subtilis BKM B-407 was determined. The antibacterial effect of the studied halogen- and nitrobenzimidazoles was compared with the antimicrobial activity of benzimidazole. Results. The antimicrobial activity of the 12 benzimidazole derivatives was established. 2-trifluoromethylbenzimidazoles containing halogen atoms in the phenylene fragment had the most pronounced inhibitory effect. The dihalogenated derivatives exhibited greater antibacterial activity than the compounds with one halogen atom in the benzene ring. 5,6-dibromo-2-(trifluoromethyl)benzimidazole was the most active compound with an MIC of 0.49 µg/mL, comparable to the commercial antibiotic tetracycline. The antibacterial activity of erythromycin is a half that of this substance. Conclusions. Polyhalogen derivatives of benzimidazole are promising compounds for the development of new antimicrobial drugs against Gram-positive bacteria.

A facile synthesis of para-quinones derived from fused benzimidazoles with a bridgehead nitrogen atom was developed. The heterocyclic quinone core formed as a result of reductive cyclization of ortho-nitroarenes containing alicyclic and aromatic azaheterocycles. Functionalization of 1,2,3,4-tetrahydro- and pyrido[1,2-a]benzimidazoles via S_EAr, condensation, and reduction reactions allowed synthesis of amino derivatives which were oxidized with KNO₃ in H₂SO₄ to obtain novel heterocyclic quinones.