Completion of the impurity profile of lymecycline: Formal identification of impurities E and F

Lymecycline is the drug substance (DS) used in the Galderma drug product Tetralysal® capsules with 7 impurities currently described in the pharmacopeia labelled as A-G. In the current monograph, the structural identity of all impurities except E and F have been formally identified. In this manuscript, through both formal synthesis and preparative chromatography, we are the first group to confirm the structural identity, response factor of Impurity F and conditions which exacerbate the formation of both impurities. •Impurities E and F have been prepared for the first time by synthesis and purification of a degraded sample of lymecycline.•Structures of E and F have been elucidated as C5a-5 dehydro-tetracycline and 4-desmethylamino tetracycline, respectively.