The similarity of human carbonic anhydrase (CA) active sites makes it difficult to design selective inhibitors for one or several CA isoforms that are drug targets. Here we synthesize a series of compounds that are based on 5-[2-(benzimidazol-1-yl)acetyl]-2-chloro-benzenesulfonamide (1a) which demonstrated picomolar binding affinity and significant selectivity for CA isoform five A (VA), and explain the structural influence of inhibitor functional groups to the binding affinity and selectivity. A series of chloro-substituted benzenesulfonamides bearing a heterocyclic tail, together with molecular docking, was used to build inhibitors that explore substituent influence on the binding affinity to the CA VA isoform.