HPLC Separation of the ZZ, ZE, EZ, and EE Geometric Isomers and EE Isomer Enantiomers of a Substituted Pentadienyl Carboxamide Using Achiral/Chiral Column Switching

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Abstract
The four geometric isomers of a substituted pentadienyl carboxamide were separated on an achiral aminopropyl column coupled with a silica precolumn. The R and S enantiomers of the biologically active EE isomer (RO 24–0238 and RO 24–2099) were resolved (Rs 1.65) on a cellulose-based chiral stationary phase (Chiracel OF). The coupled silica and aminopropyl columns were connected to the Chiralcel OF column through a six port switching valve that enabled transfer to the EE isomer to the chiral phase for enantiomer resolution. By examining the selectivity for separation of the geometric isomers of various achiral stationary phases using hexane-isopropanol mobile phases, a method was developed which linked the achiral separation of the geometric isomers with the chiral separation of the EE enantiomers.