Peptidyl aldehyde derivatives as potent and selective inhibitors of cathepsin L

A series of peptidyl aldehyde derivatives were synthesized and tested for their inhibitory effects on several cysteine proteases and a serine protease. These componds showed no inhibition for α-chymotrypsin at the concentration less than 1000 ng/ml, while they exhibited prominent inhibition for calpain II and cathepsins, especially cathepsin L.