Synthesis and Anticancer Evaluation of 4-Chloro-2-((5-aryl-1,3,4-oxadiazol-2-yl)amino)phenol Analogues: An Insight into Experimental and Theoretical Studies

We report herein the synthesis, docking studies and biological evaluation of a series of new 4-chloro-2-((5-aryl-1,3,4-oxadiazol-2-yl)amino)phenol analogues (6a-h). The new compounds were designed based on the oxadiazole-linked aryl core of tubulin inhibitors of IMC-038525 and IMC-094332, prepared in five steps and further characterized via spectral analyses. The anticancer activity of the compounds was assessed against several cancer cell lines belonging to nine different panels as per National Cancer Institute (NCI US) protocol. 4-Chloro-2-((5-(3,4,5-trimethoxyphenyl)-1,3,4-oxadiazol-2-yl)amino)phenol (6h) demonstrated significant anticancer activity against SNB-19 (PGI = 65.12), NCI-H460 (PGI = 55.61), and SNB-75 (PGI = 54.68) at 10 µM. The compounds were subjected to molecular docking studies against the active site of the tubulin–combretastatin A4 complex (PDB ID: 5LYJ); they displayed efficient binding and ligand 4h (with docking score = −8.030 kcal/mol) lay within the hydrophobic cavity surrounded by important residues Leu252, Ala250, Leu248, Leu242, Cys241, Val238, Ile318, Ala317, and Ala316. Furthermore, the antibacterial activity of some of the compounds was found to be promising. 4-Chloro-2-((5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)amino)phenol (6c) displayed the most promising antibacterial activity against both Gram-negative as well as Gram-positive bacteria with MICs of 8 µg/mL and a zone of inhibition ranging from 17.0 ± 0.40 to 17.0 ± 0.15 mm at 200 µg/mL; however, the standard drug ciprofloxacin exhibited antibacterial activity with MIC values of 4 µg/mL.