Clarithromycin lacto isomer

Clarithromycin lacto isomer is a structurally related impurity derived from the 14-membered macrolactone core of clarithromycin, featuring a hydroxyl group at position 6 and a methyl-substituted amino group at position 7. The lacto isomerization introduces a distinct stereochemical configuration at the lactone ring junction, altering the compound's conformational flexibility and hydrogen-bonding capacity. This isomer arises via acid-catalyzed ring rearrangement during synthesis or thermal degradation pathways. It serves as a critical HPLC reference standard for quantifying process-specific impurities in clarithromycin formulations.