This proposal presents a unique and novel approach to the treatment and control of viral infections. Interferon has been established as a natural inhibitor of viral protein synthesis within the infected cell. We have shown that c-AMP and certain 3',5'-cyclic monophosphate derivatives related thereto can significantly enhance the antiviral action of interferon in vitro. It is the purpose of the present proposal to prepare certain new 3',5' cyclic nucleotides related to tubercidin which will transport intracellularly and be so designed that they will resist degradation by phosphodiesterase. These nucleotides should be 50 to 100 times more potent than c-AMP in enhancing the action of interferon in its inhibition of viral infection. It is hoped that these new c-nucleotides will possess c-AMP like action in initiating the synthesis of new antiviral protein within the cell. These new analogs containing the pyrrolo(2,3-d)pyrimidine ring system should offer an excellent study in structure-activity relationship so that eventually an extremely potent c-nucleotide might be prepared for study. These c-nucleotides will first be studied in vitro as to their ability to activate c-AMP dependent protein kinase from several sources. In vitro assays will also be performed against phosphodiesterase and the best compounds be selected for study in viral infected cells. Certain selected analogs will be studied in vivo by Professor Robert W. Sidwell, Virologist at the Utah State University, Logan, Utah.