Compound 159 was further scrutinized by investigating the importance of the amide NH, and the effect of the substituent on the benzamide ring (160–164). Among them, compounds 163 and 164 exhibited the most potent enzymatic (163: IC50, 0.46 µM; 164: IC50, 1.23 µM) and cell‐based antiviral (163: EC50, 6.0 µM; 164: EC50, 5.2 µM) activities.