Velpatasvir Intermediate 1

Velpatasvir Intermediate 1 is a structurally related API impurity derived from the pyrazine-piperazine core of velpatasvir, featuring a substituted benzimidazole moiety and a terminal hydroxyl group in lieu of the final drug's esterification. The compound retains the 4-amino-1H-pyrazolo[3,4-b]pyridine scaffold but lacks the C-terminal methoxybenzyl ester, presenting a free carboxylic acid functionality. This intermediate serves as a critical synthetic precursor in the velpatasvir pathway, enabling regioselective coupling during late-stage API synthesis. It functions as an HPLC reference standard for impurity profiling in velpatasvir drug substance analysis.