Rosuvastatin 3R,5R-Isomer calcium

Rosuvastatin 3R,5R-Isomer calcium is a stereoisomeric calcium salt derived from the chiral centers at positions 3 and 5 of the Rosuvastatin core structure. It retains the pyrimidine-5-carboxylic acid sulfonamide moiety and fluorinated cyclohexyl substituent characteristic of the parent drug but exhibits distinct stereochemistry, conferring unique physicochemical properties. The calcium coordination modifies its solubility profile and stability under analytical conditions. This isomer arises as a synthetic byproduct during enantiomeric resolution processes of Rosuvastatin. It serves as an HPLC reference standard for quantifying stereoisomeric impurities in Rosuvastatin active pharmaceutical ingredient batches.