To prepare the derivatives, abacavir, acyclovir, adefovir, amantadine, amprenavir, darunavir, didanosine, oseltamivir, penciclovir, and tenofovir were used as mother ligand molecules, respectively. The functional group of each mother ligand molecule was substituted by Cl, F, NCH3, N(CH3)2, OH-, NH2-, HOOC-, or NO- [40 ]. Since there were no methods to predict which functional group that could increase the antiviral activity, its selection was based on ‘trial and error’ principles.