Tuning and predicting biological affinity: aryl nitriles as cysteine protease inhibitors

A series of aryl nitrile-based ligands were prepd. to investigate the effect of their electrophilicity on the affinity against the cysteine proteases rhodesain and human cathepsin L. D. functional theory calcns. provided relative reactivities of the nitriles, enabling prediction of their biol. affinity and cytotoxicity and a clear structure-activity relationship.