Linagliptin Impurity V

Linagliptin Impurity V is a de-methylated analog of the parent DPP-4 inhibitor, featuring a 5-(4-((3R)-3-amino-1-oxo-1H-benzotriazol-5-yl)butyl)-2,3-dihydro-1,4-benzothiazepin-2-yl)carbamic acid tert-butyl ester core. The absence of the N-methyl substituent on the benzotriazole moiety distinguishes it structurally, rendering a primary amine functionality instead of the tertiary amine present in linagliptin. This impurity arises during synthetic pathways involving incomplete alkylation steps. It serves as a critical HPLC reference standard for quantifying process-related impurities in linagliptin active pharmaceutical ingredient batches.