Montelukast Sodium EP Impurity A

Chemical Name: 1-[[[(1S)-1-[3-[(1E)-2-(7-Chloro-2-quinolinyl)ethenyl]phenyl]-3-[2-(1-hydroxy-1-methylethyl)phenyl]propyl]sulfanyl]methyl]cyclopropyl]acetic acid sodium salt (as per EP);