Velpatasvir R Isomer is a stereoisomeric impurity of the antiviral agent velpatasvir, characterized by an inverted configuration at the chiral center adjacent to the pyrazine core. The molecule incorporates a substituted piperazine ring linked via an amidine bridge, with a methoxyphenyl ether substituent and a pyridine moiety. Its structural divergence from the parent drug arises from the R-configuration at the key stereocenter, which disrupts the optimal pharmacophore alignment. This impurity is synthesized via enantioselective catalytic hydrogenation of a prochiral intermediate. It serves as a critical HPLC reference standard for enantiomeric purity analysis in velpatasvir API batches.
