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2,2’‐Diformyl‐1,1’‐binaphthyl is found to exhibit highly enantioselective fluorescence enhancement in the presence of various β‐amino alcohols and base. It provides a new method to determine the enantiomeric composition of those substrates and has potential for high throughput analysis. Based on detailed spectroscopic analyses, it is proposed that a stereoselective cyclization of a β‐amino alcohol with the probe should occur to form a rigid macrocyclic intermediate, contributing to the greatly enhanced fluorescence.

 

The enantiomers of chiral amino acids play versatile roles in biological systems including humans. They are also very useful in the asymmetric synthesis of diverse chiral organic compounds. Therefore, identifying a specific amino acid and distinguishing it from its enantiomer are of great importance. Although significant progress has been made in the development of fluorescent probes for amino acids, most of them are not capable of conducting simultaneous chemoselective and enantioselective detection of a specific amino acid enantiomer. In this article, several fluorescent probes have been designed and synthesized for chemoselective as well as enantioselective recognition of certain amino acid enantiomers. ( S )-1 shows greatly enhanced fluorescence in the presence of l -glutamic acid and l -aspartic acid, but produces no or little fluorescence response toward their opposite enantiomers and other amino acids. ( R )-4 in combination with Zn 2+ shows greatly enhanced fluorescence in the presence of l -serine. ( S )-6 is designed for the selective recognition of histidine. Micelles made of an amphiphilic diblock copolymer are used to encapsulate the water-insoluble compound ( S )-8 which shows chemoselective as well as enantioselective fluorescence enhancement with l -lysine in the presence of Zn 2+ in aqueous solution. The same micelles are also used to encapsulate several ( S )-1,1′-binaphthyl-based monoaldehydes ( S )-10 for the chemoselective and enantioselective fluorescence recognition of l -tryptophan in the presence of Zn 2+ in aqueous solution. These findings have demonstrated that highly selective fluorescence identification of a specific amino acid enantiomer can be achieved by incorporating certain functional groups at the designated locations of the 1,1′-binaphthyls. The binaphthyl core structure of these probes provides both a chirality source and highly tunable fluorescence properties. Matching the structure and chirality of these probes with those of the specific amino acid enantiomers can generate structurally rigid reaction products and give rise to greatly enhanced fluorescence. The strategies of this work can be further expanded to develop fluorescent probes for the specific identification of many amino acids of interest. This should facilitate the analysis of chiral amino acids in various applications. The outlook of this research and its comparison with other methods are also discussed. 

A chemoselective as well as enantioselective fluorescent probe has been developed to determine both the concentration and enantiomeric composition of the biologically important amino acid histidine by measuring the fluorescence responses when excited at two different wavelengths. 

A highly chemoselective as well as enantioselective fluorescent probe has been discovered for the recognition of the acidic amino acids, including glutamic acid and aspartic acid. This study has established a novel amino acid recognition mechanism by an aldehyde-based fluorescent probe. 

A series of BINOL-based monoaldehydes have been designed and synthesized as fluorescent probes for l - and d -tryptophan. It is found that in the presence of a diblock copolymer PEG-PLLA, these probes can be encapsulated into micelles which in combination with Zn 2+ have exhibited chemo- and enantioselective fluorescent enhancement with tryptophan in aqueous media.