Velpatasvir impurity 1

Velpatasvir impurity 1 is a structurally related byproduct arising from the synthetic pathway of the antiviral agent velpatasvir. It retains the core pyrazine-sulfonamide scaffold but features a truncated alkyl chain substitution at the 5-position, replacing the ethyl group with a hydrogen atom. This modification introduces a distinct hydrophobic profile while maintaining key hydrogen-bonding capabilities via the sulfonamide moiety. The compound serves as a critical HPLC reference standard for monitoring synthetic consistency and degradation pathways in velpatasvir formulations.