(S)-Indacaterol

(S)-Indacaterol is the enantiomerically pure (S)-configured oxazolidinone derivative of the long-acting β2-agonist indacaterol, featuring a 3-indolyl-5-naphthyl oxazolidin-2-one core with a (S)-stereochemistry at the chiral center. This impurity arises from partial enantiomeric resolution during the synthesis of the parent drug, differing solely in the spatial orientation of the oxazolidinone ring. It serves as an HPLC reference standard for enantiomeric purity analysis of indacaterol APIs.