Synthesis and biological evaluation of pyrrolidine-functionalized nucleoside analogs

Inhibition of viral reverse transcriptases and mammalian DNA polymerases by unnatural nucleoside analogs is a proven approach in antiviral and anticancer therapy, respectively. The majority of current nucleoside drugs retain the canonical nucleobase structure, which is fused to an unnatural sugar. In the present work, a series of novel pyrrolidine-functionalized purine and pyrimidine nucleosides was prepared via PyBOP-catalyzed SNAr addition-elimination reactions of commercial halogenated precursors and tested for their antiviral and anticancer activity. The newly synthesized nucleoside analogs showed limited biological activity, probably as a result of their poor cellular uptake and their inefficient bioactivation to the corresponding nucleoside monophosphates. A phosphoramidate prodrug had an improved cell permeability and was metabolized to the nucleoside monophosphate form in human cells, as revealed by HPLC-MS/MS analyses.