Novel 6-azapyrimidine-2'-deoxy-4'-thionucleosides: synthesis, biological evaluation and conformational analysis.

We report the synthesis of novel 1-(2'-deoxy-4'-thio-beta-D-erythro-pentofuranosyl)-(6-azapyrimidine) nucleosides and the subsequent preparation of a series of N3-substituted analogues. All the novel compounds were evaluated against a range of viruses, however they lacked any measurable activity. The lack of anti-herpetic activity may be a result of the parent nucleoside having poor affinity for herpes simplex virus type 1 thymidine kinase. Conformational analysis of the parent nucleoside showed a twist (3T2) sugar conformation commonly displayed by 2'-deoxy-4'-thionucleosides and the anti-human immunodeficiency virus type 1 agents zidovudine and 3'-fluoro-ddT.