Alkylamino derivatives of N-benzylpyrazine-2-carboxamide: synthesis and antimycobacterial evaluation

A series of alkylamino derivatives of N-benzylpyrazine-2-carboxamide was designed, synthesized and assayed in vitro for their antimycobacterial, antibacterial, antifungal as well as antiviral activities. Final structures were prepared from 6-chloro (1), 5-chloro (2) or 3-chloro (3) derivatives of N-benzylpyrazine-2-carboxamide by nucleophilic substitution of chlorine with n-alkylamines in the range from butylamine to octylamine (labelled a-e). Series 1a-e and 2a-e exerted higher activity against Mycobacterium tuberculosis H37Rv compared to the corresponding pattern compounds and the reference compound pyrazinamide. The most active derivatives reached an activity MIC = 4.6-10 mu M (M. tbc H37Rv). More importantly, activity was also observed against other tested mycobacterial strains (including drug-resistant strains). Substitution of 3-chlorine was disadvantageous and led to completely inactive compounds 3a-e. Some compounds showed activity against Gram-positive bacterial strains (including MRSA) or influenza virus, but no antifungal activity was observed.