Velpatasvir Intermediate-I SS-Isomer

Velpatasvir Intermediate-I SS-Isomer is a stereoisomeric byproduct arising during the synthesis of the NS5A inhibitor Velpatasvir, characterized by a (2S,4S)-configured piperazine core linked to a substituted tetrahydrofuran moiety. The compound features a tertiary amine, two adjacent chiral centers, and a 2-hydroxy-4-methylthiazole side chain, conferring distinct diastereomeric properties compared to the parent drug. Its SS-configuration introduces steric hindrance critical during key coupling steps, leading to regioselective impurity formation. This intermediate serves as an HPLC reference standard for quantifying stereoisomeric impurities in Velpatasvir API batches.