High performance liquid chromatographic enantioseparation of chiral bridged polycyclic compounds on chiralcel OD‐H and chiralpak OT(+)

The HPLC enantiomeric separation of 29 racemic bridged polycyclic compounds was examined on commercially available Chiralcel OD‐H and Chiralpak OT(+) columns. The separations were evaluated under normal‐phase mode (hexane containing mobile phase) for Chiralcel OD‐H and under normal‐phase as well as under reversed‐phase mode (pure MeOH, temperature 5°C) for Chiralpak OT(+). Almost all compounds were resolved either on Chiralcel OD‐H or on Chiralpak OT(+), in some cases on both. The use of trifluoroacetic acid (TFA), as modifier of the hexanic mobile phase, had a beneficial effect on the enantioseparation of some polar and acidic compounds on Chiralcel OD‐H. The influence of small chemical structural modifications of the analytes on the enantioseparation behavior is discussed. A structure–retention relationship has been observed on both stationary phases. This chromatographic evaluation may provide some information about the chiral recognition mechanism: in the case of Chiralcel OD‐H, hydrogen bonding, π‐π and distereoselective repulsive are supposed to be the major analyte‐CSP interactions. In the case of Chiralpak OT(+), a reversed‐phase enantioseparation could take place through hydrophobic interactions between the aromatic moiety of the analytes and the chiral propeller structure of the CSP. The synthesis of some unknown racemic bromobenzobicyclo[2.2.1] analytes is also described. Chirality, 2009. © 2008 Wiley‐Liss, Inc.