Enantioselective sensing of amino acids by copper(II) complexes of phenylalanine-based fluorescent β-cyclodextrins

The synthesis and full characterisation of two modified cyclodextrins 6-deoxy-6-N-[Nα-(N2-dansylaminoethyl)-R-(or S)-phenylalaninamide]-β-cyclodextrin, containing a metal binding site and a dansyl fluorophore, are described. Both cyclodextrins were shown to form copper(II) complexes with fluorescence quenching. Addition of d- or l-amino acids to the copper(II) complexes induced a ‘switch on’ of the fluorescence which was enantioselective for Pro, Phe and Trp. The enantioselective fluorescence effect was used for the determination of the optical purity of proline.