Many efforts have been undertaken to make derivatives of
amantadine in order to find new M2 inhibitors against these mutant
M2 proteins Fig. 2). Replacement of the amine group with
pyrrolidine, azetidine, and aziridine rings did not lead to compounds
with better antiviral activities11–13. In 2010, Zarubaev, et al.14,
reported a tetrazole derivative of adamantane (1) which exhibits a
highly potent antiviral activity against a rimantadine-resistant
influenza strain containing a S31N mutation. More recently,
DeGrado and coworkers15 rationally designed a spirane-
adamantane derivative (2) with potent efficacy against both the
V27A and L26P mutant strains of influenza virus with an activity
comparable to amantadine to the wide-type strain. They also further
developed the arylmethyl substituted amantadine derivative
M2WJ332 (3) and the benzyl-substituted derivative (4). These
two compounds showed both inhibitory activity against S31N and
wild type M2 proteins. Notably, M2WJ332 has shown an even