Enantiomeric Separation Of Several Oxirane Derivatives By High Performance Liquid Chromatography On Polysaccharide-Based Chiral Stationary Phases

Five polysaccharide based chiral stationary phases have been used for separation of enantiomers of fourteen heterocyclic oxiranes. The polysaccharide based chiral stationary phases used in this study are Chiralak AD, Chiralpak AS, Chiralcel OD, Chiralcel OG, and Chiralcel OJ. From the chiral separation results, the chiral separation ability for the selected compounds show the order of Chiralpak AD > Chiralcel OD > Chiralcel OJ > Chiralcel OG > Chiralpak AS. Chiralcel OD appears to be quite versatile, since 8 out of 11 oxiranes with pi-aromatic system were successfully resolved, yet no resolution was obtained for those oxirane derivatives, which lacks the pi-aromatic system. Although Chiralcel OD is also versatile, it was not as effective; since the separation factors (alpha) are much smaller. The results indicate that dipole interactions have a strong impact on the retention mechanism, and extended pi systems are essential. The spatial arrangement of the substituent groups around the analyte stereogenic center plays an important role in enantiomeric separations. The closer a group is to the chiral center, the more likely is the chiral recognition and enantioselectivity.