Structure Assignment of a Pharmacopeial Impurity of Meloxicam

The most characteristic impurity of the meloxicam drug substance is an N-methylated derivative, equally formed in the various known manufacturing syntheses of the compound. An N-methylated impurity is listed in the European Pharmacopeia monograph of meloxicam as Impurity C, although no evidence has been published for its structure. An unambiguous structure proof of the N-methylated impurity formed in our manufacturing synthesis is disclosed in the present paper, demonstrating its identity with Impurity C.