Montelukast Sodium Imp. D and E (EP): 1-[[[(1R or IS)-1-[3-[(1R)-1-[[[1-(carboxymethyl) cyclopropyl] methyl]thio]-2-(7-chloro-2-quinolinyl)ethyl]phenyl]-3-[2-(1-hydroxy-1-methylethyl)phenyl]propyl]thio]methyl]-Cyclopropaneacetic acid.