New 1 H ‐indole‐2,3‐dione 3‐thiosemicarbazones with 3‐sulfamoylphenyl moiety as selective carbonic anhydrase inhibitors

1-Methyl/ethyl/benzyl-5-(un)substituted 1H-indole-2,3-diones (2, 3, and 4) were synthesized by reaction of 5-(un)substituted 1H-indole-2,3-diones (1) with methyl iodide, ethyl chloride, and benzyl bromide. (3-Sulfamoylphenyl)isothiocyanate (6) was obtained by the treatment of 3-aminobenzenesulfonamide (5) with thiophosgene. Compound 6 was reacted with hydrazine to yield 4-(3-sulfamoylphenyl)thiosemicarbazide (7). Novel 1-(un)substituted/methyl/ethyl/benzyl-5-(un)substituted 1H-indole-2,3-dione 3-[4-(3-sulfamoylphenyl)thiosemicarbazone] derivatives (8-11) were prepared by condensation of 7 and 1-4. The structures of the synthesized compounds were confirmed by elemental analysis and spectral data. Inhibition of the widely distributed cytosolic off-targets human carbonic anhydrases (hCAs) I and II, and two tumor-associated membrane-bound isoforms (hCAs IX and XII), by 8-11 was investigated. The hCA II inhibitory effects of all tested compounds were in the subnanomolar to low nanomolar levels (K-i = 0.32-83.3 nM), and generally high selectivity for hCA II isoenzyme over hCA I, IX, and XII isoenzymes was observed. The strongest inhibitors of hCA II, 1-benzyl-5-(trifluoromethoxy)-substituted 11c (K-i = 0.32 nM) and 1-ethyl-5-chloro-substituted 10e (K-i = 0.35 nM), were docked within the enzyme active site. Molecular modeling studies with the most effective hCA IX and XII inhibitors were also carried out.