Separation and analysis of the diastereomers and enantiomers of cypermethrin and related compounds

The diastereomers of cypermethrin and permethrin have been resolved on an irregular silica column. Complete separation of three of the four enantiomeric pairs of cypermethrin was achieved with reasonable retention times (<50 min) by direct injection of the separated diastereomers onto a cellulose based chiral HPLC column. The order of elution was established; structures were confirmed by NMR and comparison with the retention times of authentic enantiomeric standards. For the unseparated pair, improved resolution was achieved with a slightly longer retention time (80 min). injection of alpha-cypermethrin onto the chiral system under the same conditions gave excellent separation of the two enantiomers. (C) 1997 Elsevier Science B.V.