Clevidipine butyrate Impurity 1 Catalogue D155221 CAS 1801167-49-6 M.W 313.18 M.F C15H14Cl2O3 Specifications FAQs methyl 2',3'-dichloro-3-methyl-5-oxo-1,2,5,6-tetrahydro-[1,1'-biphenyl]-2-carboxylate