Synthesis and biological evaluation of chromone carboxamides as calpain inhibitors

Excessive calpain activations contribute to serious cellular damage and have been found in many pathological conditions. Novel chromone carboxamides derived from ketoamides were prepared and evaluated for μ-calpain inhibition. Among synthesized, compound 2i was the most potent calpain inhibitor with an IC50 value of 0.24 ± 0.11 μM comparable to the activity of peptide aldehyde calpain inhibitor MDL 28,170. Furthermore, compound 2i showed higher selectivity for μ-calpain over two related cysteine proteases cathepsin B and cathepsin L, suggesting the chromone ring as a good scaffold for selective μ-calpain inhibitors.