Design, Synthesis, and Antiviral Activity of Adenosine 5‘-Phosphonate Analogues as Chain Terminators against Hepatitis C Virus

A series of adenosine 5‘-phosphonate analogues were designed to mimic naturally occurring adenosine monophosphate. These compounds (1−5) were synthesized and evaluated in a cellular hepatitis C virus (HCV) replication assay. To improve cellular permeability and enhance the anti-HCV activity of these phosphonates, a bis(S-acyl-2-thioethyl) prodrug for compound 5 was prepared, and its cellular activity was determined. To elucidate the mechanism of action of these novel adenosine phosphonates, their diphosphate derivatives (1a−5a) were synthesized. Further nucleotide incorporation assays by HCV NS5B RNA-dependent RNA polymerase revealed that 2a and 3a can serve as chain terminators, whereas compounds 1a, 4a, and 5a are competitive inhibitors with ATP. Additional steady-state kinetic analysis determined the incorporation efficiency of 2a and 3a as well as the inhibition constants for 1a, 4a, and 5a. The structure−activity relationships among these compounds were analyzed, and the implication for nucleoside ph...