Syntheses and highly enantioselective fluorescent recognition of α-hydroxyl/amino carboxylic acid anions in protic solutions

The multibinding-site macrocycle R-4 was synthesized and the interactions of R-4 with various α-hydroxyl/amino carboxylate were studied in DMSO/H2O system (1:1, 0.01 M Tris–HCl buffer, pH 7.4) by fluorescence titration experiments. The sensor R-4 was found to present high enantioselective fluorescent sensing ability to α-hydroxyl/amino carboxylate. It was observed that within a certain concentration range, the senor R-4 enantioselective responded to d-α-hydroxyl/amino carboxylates rather l-α-hydroxyl/amino carboxylates according to the fluorescence intensity. The results indicated that the sensor R-4 was very promising to be used as a fluorescent sensor in determining the enantiomeric composition of α-hydroxyl/amino carboxylates in DMSO/H2O system.