Velpatasvir intermediate R-Methyl SS isomer

Velpatasvir intermediate R-Methyl SS isomer is a stereoisomeric API impurity derived from the antiviral drug Velpatasvir, featuring a chiral methyl substituent in the R-configuration and SS-diastereomerism at adjacent stereocenters. Its core structure incorporates a 2-aminopyridine moiety linked to a sulfonamide-piperazine scaffold, with a methoxy group at the 4-position of the pyridine ring. The compound arises during Velpatasvir synthesis via stereoselective alkylation steps, where stereochemical control is critical. This isomer serves as an HPLC reference standard for quantifying stereoisomeric impurities in Velpatasvir active pharmaceutical ingredients.