Substituted N-Benzylpyrazine-2-carboxamides: Synthesis and Biological Evaluation (†)

A series of twelve amides was synthesized via aminolysis of substituted pyrazinecarboxylic acid chlorides with substituted benzylamines. Compounds were characterized with analytical data and assayed in vitro for their antimycobacterial, antifungal, antibacterial and photosynthesis-inhibiting activity. 5-tert-Butyl-6-chloro-N-(4-methoxybenzyl)pyrazine-2-carboxamide (12) has shown the highest antimycobacterial activity against Mycobacterium tuberculosis (MIC = 6.25 µg/mL), as well as against other mycobacterial strains. The highest antifungal activity against Trichophyton mentagrophytes, the most susceptible fungal strain tested, was found for 5-chloro-N-(3-trifluoromethylbenzyl)-pyrazine-2-carboxamide (2, MIC = 15.62 µmol/L). None of the studied compounds exhibited any activity against the tested bacterial strains. Except for 5-tert-butyl-6-chloro-N-benzylpyrazine-2-carboxamide (9, IC(50) = 7.4 µmol/L) and 5-tert-butyl-6-chloro-N-(4-chlorobenzyl)pyrazine-2-carboxamide (11, IC(50) = 13.4 µmol/L), only moderate or weak photosynthesis-inhibiting activity in spinach chloroplasts (Spinacia oleracea L.) was detected.