Synthesis and biological activity of 4'-thio-2'-deoxy purine nucleosides

The evolution of nucleoside analogue antivirals: A review for chemists and non-chemists. Part 1: Early structural modifications to the nucleoside scaffold

This is the first of two invited articles reviewing the development of nucleoside-analogue antiviral drugs, written for a target audience of virologists and other non-chemists, as well as chemists who may not be familiar with the field. Rather than providing a simple chronological account, we have examined and attempted to explain the thought processes, advances in synthetic chemistry and lessons learned from antiviral testing that led to a few molecules being moved forward to eventual approval for human therapies, while others were discarded. The present paper focuses on early, relatively simplistic changes made to the nucleoside scaffold, beginning with modifications of the nucleoside sugars of Ara-C and other arabinose-derived nucleoside analogues in the 1960's. A future paper will review more recent developments, focusing especially on more complex modifications, particularly those involving multiple changes to the nucleoside scaffold. We hope that these articles will help virologists and others outside the field of medicinal chemistry to understand why certain drugs were successfully developed, while the majority of candidate compounds encountered barriers due to low-yielding synthetic routes, toxicity or other problems that led to their abandonment.

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This is the first of two invited articles reviewing the development of nucleoside-analogue antiviral drugs.

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It is written for a target audience of virologists and other non-chemists, and for chemists unfamiliar with the field.

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Numerous modifications have been made to the nucleoside scaffold in order to impart therapeutic benefits.

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Nucleoside modifications led to the development of potent antivirals such as acyclovir, entecavir, and tenofovir.

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We examine thought processes, progress in synthetic chemistry and results of antiviral testing that led to approved drugs.

Bis(tBuSATE) phosphotriester prodrugs of 8-azaguanosine and 6-methylpurine riboside; bis(pom) phosphotriester prodrugs of 2'-deoxy-4'-thioadenosine and its corresponding 9alpha anomer

As an extension of previous work with bis(POM) nucleotide prodrugs, we report the synthesis and biological evaluation in tumor cell culture of the bis(pivaloyloxymethyl) phosphotriester prodrug of slightly cytotoxic 2'-deoxy-4'-thioadenosine and its alpha-anomer. We have experienced need for an alternative phosphate masking group, particularly with purine nucleosides. Accordingly, we report synthesis and biological evaluation of the bis(tBuSA TE) phosphotriester prodrugs of 8-azaguanosine and 6-methylpurine riboside, nucleoside analogs with moderate to significant cytotoxicity. All four prodrugs were examined in tumor cell culture in parallel with the parent nucleosides. Synthetic routes and biological data are presented.