fexofenadine Imp-G

Fexofenadine Imp-G is a dimeric byproduct arising from the coupling of two fexofenadine molecules via their 4-hydroxy-3-methoxyphenyl moieties, forming a bis(ether) linkage. This impurity retains the core ethylamine backbone and piperidine ring of the parent drug but features an extended aromatic system with additional methoxy and hydroxy substituents. Its structural symmetry and conjugated π-system contribute to distinct chromatographic behavior. This compound serves as an HPLC reference standard for quantifying dimeric impurities in fexofenadine active pharmaceutical ingredient batches.