Enantiomer Excess Determination of Amines and Dipeptides by ESI and FAB Mass Spectrometry Coupled with the Enantiomer-Labeled Host Method

Abstract

The enantiomeric excess (e.e.) determination of organic amines and dipeptides has been examined using ESI and FAB mass spectrometry. Here, an equimolar amount of labeled and unlabeled enantiomeric host pair compounds is mixed with a given e.e.-unknown guest compound. This is called the enantiomer labeled (EL)-host method. The enantiomeric host pairs employed were (1) chiral podands having galactose end-groups and (2) chiral crown ethers. Three sets of the I_e (intensity excess)-e.e. plot showed excellent linear relationships, indicating that the e.e.-value of e.e.-unknown amine compounds can be determined by the simple ESIMS or FABMS coupled with the EL-host method, within the mean error of 1.5-4%e.e.