Amlodipine EP Impurity B

Amlodipine EP Impurity B is a structurally related dihydropyridine derivative featuring a substituted phenyl ring with a chlorine atom at the para position relative to the methoxy group, coupled with a hydroxylated ester moiety on the dihydropyridine core. This impurity arises via oxidative degradation of the parent amlodipine molecule, involving hydroxylation and esterification at the 3-position of the dihydropyridine ring. The compound retains the 2-methoxy-5-chlorobenzyl side chain but exhibits altered electronic properties due to the hydroxyl substitution. It serves as a critical HPLC reference standard for quantifying degradation products in amlodipine formulations.