Investigation of peptoid chiral stationary phases varied in absolute configuration

Based on chiral N-(1-phenylethyl) glycines, a series of peptoid chiral stationary phases (CSPs) terminated with achiral alkyl group (diisopropyl, t-butyl or n-butyl) and varied in absolute configuration of selector were investigated with nine axially chiral analytes. It is very interesting to observe that selectors with heterogeneous configuration form, such as S-R-R, S-R-S, S-S-R, generally performed better than S-S-S selectors. Moreover, longer S-R-S-R-S selector did not outperform the S-R-S one obviously, with several separations declined. In addition to the result that the elution order of most enantiomers depends on the asymmetric center adjacent to the terminus of selector, we presume that the moieties around this chiral center are the most important absorbing sites for chiral discrimination; the terminal group and other chiral blocks in selector may assist enantiorecognition by constructing appropriate conformation. Various terminal alkyl groups also resulted in a few differences in enantioselectivity.