Clarithromycin impurity D

Clarithromycin impurity D is a degradation byproduct formed via oxidative cleavage of the 14-membered lactone ring in Clarithromycin, yielding a truncated macrocyclic core with a hydroxylated side chain at the C-9 position. The structure retains the characteristic macrolide backbone but exhibits a modified glycosylated substituent and an additional hydroxyl group, distinguishing it from the parent compound. This impurity arises during thermal or oxidative stress conditions and is utilized as an HPLC reference standard for quantifying degradation pathways in Clarithromycin drug substance analysis.