Development of Novel Isatin-Tethered Quinolines as Anti-Tubercular Agents against Multi and Extensively Drug-Resistant Mycobacterium tuberculosis
Mohamed A. Abdelrahman, Hadia Almahli, Tarfah Al‐Warhi, Taghreed A. Majrashi, Marwa M. Abdel‐Aziz, Wagdy M. Eldehna, Mohamed A. Said
Abstract
We describe the design and synthesis of two isatin-tethered quinolines series (Q6a–h and Q8a–h), in connection with our research interest in developing novel isatin-bearing anti-tubercular candidates. In a previous study, a series of small molecules bearing a quinoline-3-carbohydrazone moiety was developed as anti-tubercular agents, and compound IV disclosed the highest potency with MIC value equal to 6.24 µg/mL. In the current work, we adopted the bioisosteric replacement approach to replace the 3,4,5-trimethoxy-benzylidene moiety in the lead compound IV with the isatin motif, a privileged scaffold in the TB drug discovery, to furnish the first series of target molecules Q6a–h. Thereafter, the isatin motif was N-substituted with either a methyl or benzyl group to furnish the second series Q8a–h. All of the designed quinoilne-isatin conjugates Q6a–h and Q8a–h were synthesized and then biologically assessed for anti-tubercular actions towards drug-susceptible, MDR, and XDR strains. Superiorly, the N-benzyl-bearing compound Q8b possessed the best activities against the examined M. tuberculosis strains with MICs equal 0.06, 0.24, and 1.95 µg/mL, respectively.