Synthesis, Characterization, and Inhibitory Activities of Nucleoside α,β-Imido Triphosphate Analogues on Human Immunodeficiency Virus-1 Reverse Transcriptase

Six deoxynucleoside triphosphate (dNTP) analogues were synthesized, having the α,β-P-O-P bond replaced with an imido (P-N-P) functionality. They were all shown to be reasonably potent inhibitors of human immunodeficiency virus-1 reverse transcriptase (HIV-1 RT). This has permitted, for the first time, an estimate of the relative binding affinities of the parent triphosphates (dATP, TTP, dGTP, and dCTP) toward the enzymeʹs active site, in that they can be compared indirectly by correlation with the behavior of their α,β-imido analogues. Other complicating processes such as consecutive incorporation into the growing DNA chain can be excluded because the imido linkage cannot be cleaved by HIV-1 RT. The 5-iodo analog of deoxyuridine triphosphate (IdUMPNPP,5) was the most potent inhibitor, having an IC50value of 7 μM. A general route for the phosphorylation of purine and pyrimidine 5′-imidodiphosphates by pyruvate kinase was developed using phosphoenolpyruvate (PEP) as a phosphoryl group donor. Enzymatic phosphorylation was shown to be a more efficient approach than chemical methods.