Sulfonamides incorporating piperazine bioisosteres as potent human carbonic anhydrase I, II, IV and IX inhibitors.

Starting from the molecular simplification of (R) 4-(3,4-dibenzylpiperazine-1-carbonyl)benzenesulfonamide 9a, a compound endowed with selectivity for human Carbonic Anhydrase (hCA) IV, a series of piperazines and 4-aminopiperidines carrying a 4-sulfamoylbenzamide moiety as Zn-binding group have been designed and tested on human isoforms hCA I, II, IV and IX, using a stopped flow CO2 hydrase assay. The aim of the work was to derive structure-activity relationships useful for designing isoform selective compounds. These structural modifications changed the selectivity profile of the analogues from hCA IV to hCA I and II, and improved potency. Several of the new compounds showed subnanomolar activity on hCA II. X-ray crystallography of ligand-hCAII complexes was used to compare the binding modes of the new piperazines and the previously synthesized 2-benzyl-piperazine analogues, explaining the inhibition profiles.