3-Epi empagliflozin R furanose

3-Epi empagliflozin R furanose is a stereoisomeric impurity derived from empagliflozin, featuring an inverted C-3 hydroxyl configuration and a furanose ring in the R configuration. This compound retains the core glucose scaffold with a 1,5-anhydro-3,4-dihydroxy-6-(4-hydroxyphenyl) hexane-2,5-diol framework, but exhibits altered stereochemistry at the anomeric center. The furanose ring adopts a five-membered cyclic hemiacetal structure, differing from the parent drug's pyranose configuration. This impurity arises via epimerization during synthetic processes or thermal degradation pathways. It serves as a critical HPLC reference standard for quantifying C-3 positional isomer impurities in empagliflozin active pharmaceutical ingredient batches.