(S)-BINOL-based boronic ester fluorescence sensors for enantioselective recognition of α-phenylethylamine and phenylglycinol

Four chiral fluorescence sensors (S)-L1-4 incorporating boronic ester and (S)-1,1'-bi-2-naphthol (BINOL) moieties were synthesized and developed for the enantioselective recognition of alpha-phenylethylamine and phenylglycinol enantiomers. The sensor (S)-L1 shows an obvious fluorescence quenching turn-off response towards enantiomers of both alpha-phenylethylamine and phenylglycinol. Interestingly, the sensor (S)-L2 can exhibit remarkable fluorescent enhancement turn-on response behavior towards (S)alpha-phenylethylamine, but shows no response towards phenylglycinol enantiomers. The Stern-Volmer constant (K-sv) values of (S)-L1 are 0.63 x 10(3) L mol(-1) and 4.48 x 10(3) L mol(-1) for (L)-and (D)phenylglycinol, respectively, and the value of the enantiomeric fluorescence difference ratio (ef) of (S)-L2 is 4.6 for alpha-phenylethylamine, demonstrating that (S)-L2 could be used as a fluorescence sensor for simple and direct visual discrimination of organic molecule enantiomers. On the contrary, no fluorescence enantioselective recognition response could be observed when using the (S)-BINOL-based boronic ester sensors (S)-L3 and (S)-L4 incorporating bigger naphthyl or 8-methoxyquinolinyl substituent groups.