Ritonavir Impurity B

Ritonavir Impurity B is a diastereomeric byproduct arising from the partial reduction of a ketone moiety in the synthetic pathway of Ritonavir, characterized by a substituted pyrazine ring fused to a tetrahydrofuran core and a sulfonamide-linked benzyl ester. Its structure retains the 3-hydroxy-4-(phenoxy)butyl side chain but features an exo-methylene group at the cyclohexene ring junction, distinguishing it from the parent drug. This impurity serves as a critical HPLC reference standard for quantifying process-related deviations in antiretroviral drug substance purity profiling.