Synthesis and antitubercular evaluation of novel dibenzo[b,d]thiophene tethered imidazo[1,2-a]pyridine-3-carboxamides.

A series of novel dibenzo[b,d]thiophene tethered imidazo[1,2-a]pyridine carboxamides 7a-s were designed and synthesized. The required building block, 2-dibenzo[b,d]thiophenyl imidazo[1,2-a]pyridine carboxylic acid (5) was synthesized from commercial dibenzo[b,d]thiophene in good yields following five-step reaction sequence. The desired carboxamides 7a-s was prepared through coupling of acid 5 with various benzyl amines. All the new analogues 7a-s was characterized by their NMR and mass spectral analysis. Among nineteen new compounds 7a-s screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv, three compounds 7k (MIC: 0.78μg/mL); 7e and 7n (MIC: 1.56μg/mL) were identified as potent analogues with low cytotoxicity. The results reported here will help global efforts for identification of potential lead antimycobacterial agents.