Amlodipine EP Impurity I Catalogue A236739 CAS 331258-31-2 M.W 481.97 M.F C23H32CIN3O6 Specifications FAQs diethyl 2,6-bis((2-aminoethoxy)methyl)-4-(2-chlorophenyl)-1,4-dihydropyridine-3,5-dicarboxylate