Nucleosides .8. Synthesis of 2',3'-dideoxy- and 2',3'-didehydro-2',3'-dideoxyisoguanosine as potential antiretroviral agents

2',3'-Didehydro-2',3'-dideoxyisoguanosin (2) and 2',3'-dideoxyisoguanosine (3) have been synthesized by utilizing the Corey-Winter approach starting from isoguanosine. The 6-amino and 5'-hydroxy biprotected isoguanosine derivative was converted to the corresponding 2',3'-thionocarbonate, which was heated with triethyl phosphite to afford the 2',3'-olefinic product. Either a tert-butyldimethylsilyl or a 4,4'-dimethoxytrityl group was used in the protection of 5'-hydroxy function. Compounds 2 and 3 were found inactive against human immunodeficiency virus (HIV), human cytomegalovirus (HCMV), and herpes simplex virus type 1 (HSV-1).