Structural optimization of salicylamide-based hemagglutinin (HA) inhibitor 1 resulted in the identification of cis-3-(5-hydroxy-1, 3, 3-trimethylcyclohexylmethylamino) benzenesulfonamide 28 and its derivatives as potent anti-influenza agents. The lead compound 28 and its 2-chloro analogue 40 can effectively prevent cytopathic effects (CPE) caused by infection of influenza A/Weiss/43 strain (H1N1) with EC50 values of 210 and 86 ...