Syntheses and SH-enzyme inhibitory activities of new epoxysuccinic acid piperazine derivatives against mu-calpain and cathepsin B.

New chiral epoxysuccinic acid derivatives 5 approximately 23 bearing various amino acids and N-substituted piperazines were synthesized to evaluate their inhibitory activities against mu-calpain and cathepsin B. After screening these compounds, 1-[(2S,3S)-epoxysuccinyl-L-leucyl]-4-(2-chlorophenyl)piperazine 9 proved to exhibit fairly strong inhibitory activity against both cysteine proteases. L-Valyl derivative 19 exhibited selective inhibitory activity against cathepsin B in comparison with that against mu-calpain.