Linagliptin S isomer

Linagliptin S isomer is the non-active enantiomer of the DPP-4 inhibitor linagliptin, characterized by the (S)-configuration at the chiral pyrrolidin-2-one center. It retains the core structure of the parent drug, including a substituted biphenyl group, a sulfonamide linkage, and a pyrrolidinone ring, but exhibits distinct stereochemistry that confers reduced pharmacological activity. This impurity arises during enantioselective synthesis or racemic resolution processes. Its structural similarity enables competitive inhibition in chiral HPLC analysis, serving as a critical reference standard for enantiomeric purity assessment in pharmaceutical development.