Dimethyl-4-(2-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate which is impurity of amlodipine besilate was synthesized. Hantzsch condensation of methyl acetoacetate with O-chlorobenzadehyde in isopropanol at reflux temperature for about 10 hours yielded the yellow powder. This product was purified by column chromatography and the structure was identified by spectrocospic methods (IR, MS, NMR), that was characterised amlodipine impurity G (dimethyl -4-(2-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate).
The quality of the impurity was determined by high performance liquid chromatography method validation according to The International Conference on Harmonisation (ICHQ2A) and established impurity reference standard as World Health Organization (WHO technical series 941) and determined homogeneity and assigned value as International Organisation for Standardisation (ISO 13528).
Keywords: Hantzsch condensation, amlodipine impurity G, WHO, ISO 13528.