On the basis of the lead compound 4-(N-acetylamino)-3-guanidinobenzoic acid (BANA 113), which inhibits influenza A sialidase with a K i of 2.5 μM, several novel aromatic inhibitors of influenza sialidases were designed. In this study the N-acetyl group of BANA 113 was replaced with a 2-pyrrolidinone ring, which was designed in part to offer opportunities for introduction of spatially directed side chains that could potentially interact with the 4-, 5-, ...