Synthesis of benzamide derivatives with thiourea-substituted benzenesulfonamides as carbonic anhydrase inhibitors.

The novel compounds with the chemical structure of N-({4-[N'-(substituted)sulfamoyl]phenyl}carbamothioyl)benzamide (1a-g) and 4-fluoro-N-({4-[N'-(substituted)sulfamoyl]phenyl}carbamothioyl)benzamide (2a-g) were synthesized as potent and selective human carbonic anhydrase (hCA) I and hCA II candidate inhibitors. The aryl part was changed to sulfacetamide, sulfaguanidine, sulfanilamide, sulfathiazole, sulfadiazine, sulfamerazine, and sulfametazine. The Ki values of compounds 1a-g were in the range of 20.73 ± 4.32 to 59.55 ± 13.07 nM (hCA I) and 5.69 ± 0.43 to 44.81 ± 1.08 nM (hCA II), whereas the Ki values of compounds 2a-g were in the range of 13.98 ± 2.57 to 75.74 ± 13.51 nM (hCA I) and 8.15 ± 1.5 to 49.86 ± 6.18 nM (hCA II). Comparing the Ki values of the final compounds and acetazolamide, compound 1c with the sulfanilamide moiety (Ki  = 5.69 ± 0.43 nM, 8.8 times) and 2f with the sulfamerazine moiety (Ki  = 8.15 ± 1.5 nM, 6.2 times) demonstrated promising and selective inhibitory effects against the hCA II isoenzyme, the main target protein in glaucoma. Furthermore, compounds 1d (Ki  = 20.73 ± 4.32, 4 times) and 2d (Ki  = 13.98 ± 2.57, 5.9 times), which have the sulfathiazole moiety, were found as potent hCA I inhibitors. Compounds 1c and 2f can be considered as the lead compounds determined in the present study, which can be investigated further to alleviate glaucoma symptoms.