Diltiazem Ep imp-G

Diltiazem Ep imp-G is a stereoisomeric impurity derived from the parent calcium channel blocker diltiazem, featuring an epimeric inversion at the chiral center adjacent to the 1,4-dihydropyridine core. This structural alteration introduces distinct diastereomeric configurations while preserving the sulfonamide and methoxyphenyl moieties. The compound retains the characteristic thiazine ring system but exhibits altered conformational flexibility, impacting its pharmacokinetic profile. It is synthesized as a byproduct during asymmetric synthesis steps involving chiral catalysts. This impurity is employed as an HPLC reference standard for quantifying epimeric variants in diltiazem drug substance batches.