Linagliptin Regio isomer

Linagliptin Regio isomer is a structurally distinct isomer of the antidiabetic agent linagliptin, characterized by a pyrazine core linked to a tetrahydropyridine ring with an alternative positioning of the amino substituent relative to the parent compound. This isomer exhibits a unique spatial arrangement of the sulfonamide and aromatic moieties, leading to altered physicochemical properties while retaining the core scaffold. It arises as a minor byproduct during linagliptin synthesis via regioselective substitution pathways. This compound serves as a critical HPLC reference standard for impurity profiling in linagliptin drug substance characterization.