sofosbuvir D-isomer of phosphonide

The D-isomer of sofosbuvir phosphonide is a stereoisomeric impurity arising from the chiral phosphorus center in the phosphonate prodrug moiety of the parent antiviral agent sofosbuvir. It retains the uracil nucleobase and 2'-C-methylribofuranosyl structure but features the D-configuration at the phosphorus stereocenter, contrasting with the L-isomer in the active drug. This compound exhibits distinct chromatographic and reactivity profiles due to its inverted stereochemistry, necessitating precise enantiomeric resolution during quality control. It serves as a critical HPLC reference standard for enantiomeric purity assessment in sofosbuvir API synthesis.