Acyclic analogs of 2'-deoxynucleosides related to 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine as potential antiviral agents

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Abstract
A series of acyclic analogs of 2''-deoxynucleosides related in structure to 9[(1,3-dihydroxy-2-propoxy)methyl]guanine (DHPG, 1) were synthesized and evaluated for antiviral activity against herpes simplex virus type 1 (F strain). The ability of these analogs to function as substrates for the virus-specified thymidine kinase was examined. Phosphorylation by this kinase is essential for antiviral activity. Although the acyclic 4-oxopyrimidine nucleosides were substrates for the kinase, they were devoid of antiviral activity. In the purine series, most analogs similar in structure to DHPG did exhibit significantly lower antiviral activity, indicating that even small modifications in the purine substituents substantially reduce the antiviral potency. The most active agent, 2,6-diaminopurine 27, was only poorly phosphorylated by the viral kinase; therefore, its activity was most likely due to a prior enzymatic deamination to give DHPG. Evaluation of 27 in a mouse encephalitis model showed it to be nearly as potent as (1).