Enantioselective HPLC combined with spectroscopic methods: A valid strategy to determine the absolute configuration of potential β-secretase inhibitors

A direct HPLC enantioseparation of three representative compounds of a new family of potential non-peptide β-secretase inhibitors was performed on the immobilized Chiralpak IA chiral stationary phase. Semipreparative amounts of enantiopure forms were collected and submitted to stereochemical characterization. The absolute configuration was assigned by a multi-step methodology based on the combination of Mosher's method with circular dichroism (CD) spectroscopy. The results from the NMR/CD study fully correlated the configurational assignment obtained by a second approach involving single crystal X-ray diffraction.