pitavastatin 3S,5S -isomer

Pitavastatin 3S,5S-isomer is a stereoisomeric impurity derived from the parent drug's pyrrole-fused hydrogenated naphthalene core, characterized by S-configuration at C-3 and C-5 stereocenters. Its structure retains a 3β-hydroxyl group, 5α-alkyl ester, and a lactone ring, with altered stereochemistry inducing distinct chiral interactions. This isomer arises via partial racemization during synthetic resolution steps, forming a non-pharmacopoeial byproduct. It functions as a chiral HPLC reference standard for enantiomeric purity analysis in pitavastatin active pharmaceutical ingredient batches.