4-Arylbenzenesulfonamides as Human Carbonic Anhydrase Inhibitors (hCAIs): Synthesis by Pd Nanocatalyst-Mediated Suzuki-Miyaura Reaction, Enzyme Inhibition, and X-ray Crystallographic Studies

Benzenesulfonamides bearing various substituted (hetero)aryl rings in the para-position were prepared by palladium nanoparticle-catalyzed Suzuki-Miyaura cross-coupling reactions and evaluated as human carbonic anhydrase (hCA, EC 4.2.1.1) inhibitors against isoforms hCA I, II, IX, and XII. Most of the prepared sulfonamides showed low inhibition against hCA I isoform, whereas the other cytosolic isoenzyme, hCA II, was strongly affected. The major part of these new derivatives acted as potent inhibitors of the tumor-associated isoform hCA XII. An opposite trend was observed for phenyl, naphthyl, and various heteroaryl substituted benzenesulfonamides which displayed subnanomolar hCA IX inhibition while poorly inhibiting the other tumor-associated isoform hCA XII. The inhibition potency and influence of the partially restricted arylaryl bond rotation on the activity/selectivity were rationalized by means of X-ray crystallography of the adducts of hCA II with several 4-arylbenzenesulfonamides.