parecoxib butyl amide impurity

Parecoxib butyl amide impurity is a sulfonamide-linked amide derivative arising from the substitution of the methyl ester group in parecoxib with a butyl amide moiety. Its structure features a 4-pyridinylmethyl sulfonamide core connected to a benzhydryl group via an amide bond, with a four-carbon butyl chain extending from the amide nitrogen. This impurity likely forms during synthetic processes involving acyl chloride intermediates or amidation reactions. The compound serves as a critical HPLC reference standard for quantifying process-related amide impurities in parecoxib drug substance batches.