Clevidipine butyrate Impurity 3 Catalogue D155223 CAS 1898262-46-8 M.W 313.18 M.F C15H14Cl2O3 Specifications FAQs methyl 2',3'-dichloro-5-methyl-3-oxo-1,2,3,6-tetrahydro-[1,1'-biphenyl]-2-carboxylate