Mechanistic Study on a BINOL-Coumarin-Based Probe for Enantioselective Fluorescent Recognition of Amino Acids

Self-Assembled Nanotubes Based on Chiral H8-BINOL Modified with 1,2,3-Triazole to Recognize Bi3+ Efficiently by ICT Mechanism

A novel fluorescent "off" probe R-β-D-1 containing a 1,2,3-triazole moiety was obtained by the Click reaction with azidoglucose using H8-BINOL as a substrate, and the structure was characterized by 1H NMR and 13C NMR and ESI-MS analysis. The fluorescence properties of R-β-D-1 in methanol were investigated, and it was found that R-β-D-1 could be selectively fluorescently quenched by Bi3+ in the recognition of 19 metal ions and basic cations. The recognition process of Bi3+ by R-β-D-1 was also investigated by fluorescence spectroscopy, SEM, AFM, etc. The complex pattern of R-β-D-1 with Bi3+ was determined by Job's curve as 1 + 1, and the binding constant Ka of R-β-D-1 and Bi3+ was valued by the Benesi-Hildebrand equation as 1.01 × 104 M-1, indicating that the binding force of R-β-D-1 and Bi3+ was medium. The lowest detection limit (LOD) of the self-assembled H8-BINOL derivative for Bi3+ was up to 0.065 µM. The mechanism for the recognition of Bi3+ by the sensor R-β-D-1 may be the intramolecular charge transfer effect (ICT), which was attributed to the fact that the N-3 of the triazole readily serves as an electron acceptor while the incorporation of Bi3+ serves as an electron donor, and the two readily undergo coordination leading to the quenching of fluorescence. The recognition mechanism and recognition site could be verified by DFT calculation and CDD (Charge Density Difference).

Effective enantioselective recognition by steady-state fluorescence spectroscopy: Towards a paradigm shift to optical sensors with unusual chemical architecture

A series of amino acid-derived 1,2,3-triazoles presenting the amino acid residue and the benzazole fluorophore connected by a triazole-4-carboxylate spacer was studied for enantioselective recognition using only steady-state fluorescence spectroscopy in solution. In this investigation, the optical sensing was performed with D-(-) and L-(+)-Arabinose and (R)-(-) and (S)-(+)-Mandelic acid as chiral analytes. The optical sensors showed specific interactions with each pair of enantiomers, allowing photophysical responses, which were used for their enantioselective recognition. DFT calculations confirm the specific interaction between the fluorophores and the analytes corroborating the observed high enantioselectivity of these compounds with the studied enantiomers. Finally, this study investigated nontrivial sensors for chiral molecules by a mechanism different than turn-on fluorescence and has the potential to broad chiral compounds with fluorophoric units as optical sensors for enantioselective sensing.

A Racemic Naphthyl-Coumarin-Based Probe for Quantitative Enantiomeric Excess Analysis of Amino Acids and Enantioselective Sensing of Amines and Amino Alcohols

A new racemic naphthyl-coumarin-based probe was found to bind covalently with amino acids in MeOH-KOH system and thereby generates distinct CD responses. The induced strong CD signals allowed quantitative enantiomeric excess analysis of amino acids and enantioselective sensing of amines and amino alcohols. The mechanism for the reaction of the coumarin-aldehyde probe with an amino acid was investigated by CD, UV-Vis, NMR, ESI-MS analyses and ECD calculation.

Recent Advances in Organic Synthesis of 3-Amino- or 4-Aminocoumarins

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Coumarin is a privileged scaffold that contains the unique 2H-chromen-2-one motif, and its derivatives are widely distributed in nature, especially in plants. In recent years, due to their diverse pharmacological activities and remarkable photochemical properties, they have attracted significant attention from scientists, which has also prompted the research on the synthesis approaches and the availability of substrates for these compounds. This article is a brief description of the methods for the synthesis of various coumarin derivatives via two- or multi-component reactions involving 3-amino or 4-aminocoumarin reported during 2015-2021. This review may help expand the development of various analogues with coumarin as the basic unit.

Trending Topics on Coumarin and Its Derivatives in 2020

Coumarins are naturally occurring molecules with a versatile range of activities. Their structural and physicochemical characteristics make them a privileged scaffold in medicinal chemistry and chemical biology. Many research articles and reviews compile information on this important family of compounds. In this overview, the most recent research papers and reviews from 2020 are organized and analyzed, and a discussion on these data is included. Multiple electronic databases were scanned, including SciFinder, Mendeley, and PubMed, the latter being the main source of information. Particular attention was paid to the potential of coumarins as an important scaffold in drug design, as well as fluorescent probes for decaging of prodrugs, metal detection, and diagnostic purposes. Herein we do an analysis of the trending topics related to coumarin and its derivatives in the broad field of drug discovery.

Enantioselective Fluorescent Recognition of Free Amino Acids: Challenges and Opportunities

Fluorescent probes that can discriminate enantiomers of amino acids in organic media or aqueous solution are discussed. This Minireview focuses on recent progress in the studies of three classes of probes including those made of cyclodextrins, 1,1'-binaphthyl compounds, and nanomaterials, and uses them to illustrate the design strategies, applications, and limitations in this area. These probes are potentially useful for rapid analysis of asymmetric reactions for amino acid synthesis as well as the real-time imaging of amino acids in biological systems. The challenges in these applications are analyzed. Working in this field of enantioselective fluorescent recognition of amino acids offers great opportunities to make new scientific discoveries and to develop important practical applications.