Naphthalimide-Based Chiral Fluorescence Sensor Employing (S)-BINOL Unit for Highly Enantioselective Recognition of α-Amino Alcohols with Opposite Chiral Selectivity

A new naphthalimide-based fluorescent probe [(S)-1 and (S)-2] employing (S)-BINOL unit as a chiral responsive group has been designed and synthesized. Ligand (S)-1 showed greater fluorescence enhancement towards (R)-amino alcohol and the value of enantiomeric fluorescence difference (ef) ratio reached as high as 7.07 for phenylalaninol while (S)-phenylalaninol did not show much enhancement in fluorescence, whereas ligand (S)-2 showed ef value of 4.49 for phenylalaninol. The fluorescence enhancement can be attributed to imine formation and H-bonding. Further, the R/S chiral selectivity of ligands (S)-1 and (S)-2 is opposite. The chiral discrimination ability of (S)-1 and (S)-2 was tested via fluorescence, NMR and CD spectral analysis. The results indicated that the sensor (S)-1 was very promising for use as a fluorescent sensor in determining the enantiomeric composition of -amino alcohols.