Investigating the Inhibitory Properties of Diazo and Pyrazole‐Carboxamide‐Linked Benzenesulfonamides Against Carbonic Anhydrase Isoforms I, II, IX, and XII

A novel library of diazo and pyrazole-carboxamide-linked molecules containing the sulfonamide pharmacophore was developed and synthesized, yielding selective inhibitors of clinically relevant carbonic anhydrase (CA) isoforms. The synthesis method involved the production of diazonium salts from 4- and 3-aminobenzenesulfonamide precursors, followed by cyclization and further functionalization to yield structurally diverse pyrazole derivatives. All compounds were evaluated for their inhibitory efficacy against hCA I and II (cytosolic isoforms) and the tumor-associated isoenzymes hCA IX and XII; also, cytotoxicity and molecular modeling studies were conducted for the compounds. The newly synthesized hybrid compounds displayed extensive inhibitory activity, with most derivatives showing significant potency and selectivity for cancer-associated isoforms. More specifically, para-substituted analogs exhibited enhanced inhibitory properties relative to their meta-substituted counterparts. Compound 5f, with a 3,4-dichloro motif, exhibited the highest activity with a very low KI value of 1.8 nM against hCA IX, greatly surpassing the reference drug acetazolamide. Electron-withdrawing substituents improved inhibitory efficacy, whereas electron-donating groups often reduced activity. Furthermore, compounds 5f (A549: 41.17 μM; HCT116: 4.47 μM) and 6c (A549: 14.64 μM; HCT116: 4.03 μM) showed the lowest IC50 values in both cell lines. The findings emphasize diazo- and pyrazole-carboxamide-linked benzenesulfonamides as promising scaffolds for advancing isoform-selective carbonic anhydrase inhibitors.