Medicinal chemistry of (10) annulenes and related compounds. 1. 11-Azatricyclo(4.4.1.0 1,6 )undecane, 11-azatricyclo(4.4.1.0 1,6 )undeca-3,8-diene, and 11-azabicyclo(4.4.1)undeca-1,3,5,7,9-pentaene as antiviral agents.