Synthesis and Modification of Cordycepin-Phosphoramidate ProTide Derivatives for Antiviral Activity and Metabolic Stability.

In our study, Prodrug nucleoTide (ProTide) technology was applied to cordycepin to enhance its antiviral activities and metabolic stability. Using cordycepin as starting material, we developed a synthetic method to access a series of stereospecific-phosphoramidate derivatives with various ester groups. We also successfully synthesized halogenated cordycepin derivatives via stannylation. Our 17 ProTide-cordycepin derivatives were pharmacologically evaluated for their antiviral activities. Phosphorus diastereomers 22 S and 22 R showed moderate inhibitory activity against corona and influenza viruses, while these compounds and derivatives (25 S, 27 S, and 27 R) demonstrated promising antiviral efficacy against dengue virus. Pharmacological screening indicated that Sp-isomers generally exhibited slightly greater inhibitory activity than their Rp-isomer counterparts against the dengue virus. The selected ProTides were assessed for their metabolic mechanism and stability via carboxypeptidase and microsomes. The hydrolysis rate of the Rp-isomers was observed to be slightly higher than that of the Sp-isomers, and the addition of a fluorine group also modestly increased this rate and fluorinated 39 S extended its half-life compared to nonfluorinated counterparts. These findings suggested not only structure-activity relationships of cordycepin ProTide but also the comprehensive synthetic route to access cordycepin derivatives for further antiviral development.