The related 3C and 3C-like proteinase (3Cpro and 3CLpro) of picornaviruses and coronaviruses, respectively, are good drug targets. As part of an effort to generate broad- spectrum inhibitors of these enzymes, we screened a library of inhibitors based on a halopyridinyl ester from a previous study of the severe acute respiratory syndrome (SARS) 3CL proteinase against Hepatitis A virus (HAV) 3Cpro. Three of the compounds, which ...