2-Aryl-1-hydroxyimidazoles possessing antiviral activity against a wide range of orthopoxviruses, including the variola virus.

Scientific interest in orthopoxvirus infections and search for new highly effective compounds possessing antiviral activity against orthopoxviruses have significantly increased as a result of worldwide mpox outbreak in 2022. The present work deals with the synthesis of new 2-arylimidazoles exhibiting in vitro activity not only against the vaccinia virus, cowpox virus and ectromelia (mousepox) virus but also against the variola virus. Among the imidazole derivatives under consideration (1-hydroxyimidazoles, 1-methoxyimidazoles, 1-benzyloxyimidazoles, and imidazole N-oxides), the most promising antiviral activity is demonstrated by 1-hydroxyimidazoles, which may exist as two prototropic tautomers. Both of these tautomers may be manifested in different crystal structures of these compounds, according to single-crystal X-ray diffraction analysis, while predominantly one of them (N-hydroxy-tautomeric form) is present in DMSO-d 6 solutions and in the gaseous state, as shown by NMR spectroscopy and quantum-chemical calculations. The leader compound 1-hydroxy-2-(4-nitrophenyl)imidazole 4a demonstrated the highest selectivity indices against the vaccinia virus (SI = 1072) and the variola virus (SI = 373).