Excessive calpain activation contributes to serious cellular damage in many pathological conditions. The involvement of mu-calpain in neurological disorders such as, stroke and Alzheimer's disease has attracted considerable interest in the use of calpain inhibitors as therapeutic agents. 6-Pyridone 2-carboxamides derived from ketoamides were synthesized as conformationally constrained structures resembling the well known peptidic mu-calpain inhibitor, MDL 28,170, and their mu-calpain inhibitory activities were evaluated. Of the compounds synthesized, compound 2a, which has a primary amide at warhead region of the inhibitor most potently inhibited mu-calpain with an IC(50) value of 2.81+/-1.26 microM, which is ca. 40-fold less than that of MDL 28,170.