Dipeptidyl aspartyl fluoromethylketones as potent caspase inhibitors: SAR of the N-protecting group

This article describes the synthesis and biological evaluation of a group of N-protected Val-Asp-fmk as caspase inhibitors. The protecting group was found to contribute to caspase-3 inhibiting activity, and compounds with a large group such as Cbz are more active than compounds with a small group such as Ac. Compounds with more hydrophobic protecting groups were found to be more active in cell apoptosis protection assays, probably due to increased cell permeability. MX1122, 2,4-di-Cl-Cbz-Val-Asp-fmk, is identified as a potent broad-spectrum caspase inhibitor and is selective for caspases versus other proteases, with good activity in the cell apoptosis protection assays as well as good efficacy in the mouse liver apoptosis model.