Oxcarbazapine Impurity B

Oxcarbazapine Impurity B is a synthetic byproduct arising from the incomplete methylation of the 10H-dibenz[b,f]azepine-5-carboxamide core during oxcarbazepine production. It retains the fused benzene rings and the terminal carboxamide group but lacks the 7-methoxy substitution characteristic of the parent drug, featuring instead a free phenolic hydroxyl group at the C7 position. This structural deviation creates a distinct chromophore, enabling differentiation via UV-Vis spectroscopy. The compound serves as a critical HPLC reference standard for quantifying methylation efficiency in oxcarbazepine synthesis.