Virus infections which attack animals, including man, are normally contagious afflictions which are capable of causing great human suffering and economic loss. Unfortunately, the discovery of antiviral compounds is far more complicated and difficult than the discovery of antibacterial and antifungal agents. This is due, in part, to the close structural similarity of viruses and the structure of certain essential cellular components such as ribonucleic and deoxyribonucleic acids. Nevertheless, numerous non-viral "antiviral agents", i.e. substances "which can produce either a protective or therapeutic effect to the clear detectable advantage of the virus infected host, or any material that can significantly enhance antibody formation, improve antibody activity, improve non-specific resistance, speed convalescence or depress symptoms" [Herrman et al., Proc. Soc. Exptl. Biol. Med., 103, 625 (1960)], have been described in the literature. The list of reported antiviral agents includes, to name a few, interferon and synthetic materials such as amantadine hydrochloride, pyrimidines, biguanides, guanidine, pteridines and methisazone. Because of the rather narrow range of viral infections that can be treated by each of the antiviral agents commercially available at the present time, new synthetic antiviral agents are always welcomed as potentially valuable additions to the armamentarium of medical technology.
U.S. Pat. No. 3,906,044 discloses the antiviral activity of certain adamantyl amidine compounds of the formula: ##STR1## wherein n is 0 or 1, and Ad is adamantyl or bridgehead carbon atom-substituted alkyladamantyl. The antiviral activity of the compound N-[bis-phenyl-(2-methoxy-5-chloro-phenyl)-methyl]acetamidine is disclosed in British Patent No. 1,426,603.