Design and synthesis of dipeptidyl α′,β′-epoxy ketones, potent irreversible inhibitors of the cysteine protease cruzain

The dipeptidyl epoxy ketone 4 is a potent, irreversible inhibitor of cruzain, a cysteine protease isolated from Trypanosoma cruzi, with an apparent second order inhibition rate constant of 330,000 sec−1M−1.