Determination of the enantiomeric composition of chiral amines based on the quenching of the fluorescence of a chiral calixarene

The synthesis of three chiral calixarene derivatives is described. One of these, an (S)-di-2-naphthylprolinol tetramer, is shown to exhibit significant ability to discriminate between enantiomers of l-phenylethylamine (PEA) and norephedrine on the basis of the quenching of the (S)-di-2-naphthylprolinol fluorescence emission in chloroform. The chiral discrimination appears to arise from preorganization of the four (S)-di-2-naphthylprolinol substituents on the calixarene, which define a three-dimensional chiral space. The ability to measure the enantiomeric composition of PEA and norephedrine to within an error of 4.1% and 2.6%, respectively, on the basis of a single fluorescence measurement is demonstrated.