Montelukast EP Impurity C

[1-[[[1-[3-[(E)-2-(7-Chloroquinolin-2-yl)ethenyl]phenyl]-3-[2-(1-hydroxy-1-methylethyl)phenyl]propyl]sulfinyl]methyl]cyclopropyl]acetic acid; Montelukast Sulfoxide (Mixture of Diastereomers); Montelukast Sulfoxide Impurity (USP);