Amantadine derivatives have been the only drugs marketed as M2 inhibitors of influenza A for decades. The identification of pinanamine as a novel M2 inhibitor suggests that M2 ion channels can accommodate more types of hydrophobic scaffolds. Herein, we further investigated the M2 ion channels and identified camphor derivatives as new types of M2 inhibitors. Compound 18 was found to be more potent than amantadine against wild-type influenza virus. The molecular docking revealed that compound 18 occupies more space in the M2 ion channel than amantadine and thus exhibits enhanced activity.

3-Pinanamine is a prevalent motif in medicinal chemistry and asymmetric synthesis. In line with the pursuit of novel 3-pinanamine based anti-influenza virus A agent, the direct functionalization of 3-pinanamine was achieved by using Pd-catalyzed C(sp3)–H activation logic. Good substrate scope and functional group tolerance were observed. The reaction represents a rare example of a direct functionalization of an aliphatic amine at the remote δ position.