On enantioselective separation of phenoxypropionates using permethylated β-cyclodextrin HPLC and GC columns

Investigations on chiral phenoxypropionates using permethylated β-cyclodextrin HPLC and GC columns showed a decrease in enantioselective separation efficiency from mecoprop-methyl and dichlorprop-methyl to the threefold chlorinated fenoprop-methyl. This corresponded to decreasing electron density in the aromatic system due to the increasing negative inductive effect of 3 chlorine substituents. Investigation on methyl-(RS)-2-(2,4-dichloro-3,6-dinitrophenoxy)-propionate confirmed the influence of electrophilic substituents while determination of ethyl-(RS)-2-methoxypropionate emphasized the necessity of an aromatic system for enantioselective separation on β-cyclodextrin stationary phases. For fenoprop-methyl as well as for the aryloxyphenoxypropionates diclofop-methyl and fluazifop-butyl, reversed phase HPLC showed higher separation performance than high resolution capillary GC.