Calpain is a cytosolic cysteine endopeptidase that has been implicated in a number of disorders including cancer. We have synthesized and studied the μ-calpain inhibitory activity and cytotoxicity of peptidyl aldehydes and peptidyl α-ketoamides with N-substituted d- proline or l-thiaproline residues at the P2-postion. The most potent and most selective members of the series were (R)-1-(4-nitrophenylsulfonyl)-N-((R, S)-1-oxo-3-phenylpropan ...
