Ultrasound-promoted specific chiroptical sensing of cysteine in aqueous solution and cells

Stereochemistry of Chiral 2-Substituted Chromanes: Twist of the Dihydropyran Ring and Specific Optical Rotation

Chiral 2-substituted chromanes are important substructures in organic synthesis and appear in numerous natural products. Herein, the correlation between specific optical rotations (SORs) and the stereochemistry at C2 of chiral 2-substituted chromanes was investigated through data mining, quantum-chemical calculations using density functional theory (DFT), and mechanistic analyses. For 2-aliphatic (including acyloxy and alkenyl) chromanes, the P-helicity of the dihydropyran ring usually corresponds to a positive SOR; however, 2-aryl chromanes with P-helicity tend to exhibit negative SORs. 2-Carboxyl (including alkoxycarbonyl and carbonyl) chromanes often display small experimental SORs, and theoretical calculations for them are prone to error because of the fluctuating conformational distribution with computational parameters. Several typical compounds were discussed, including detailed descriptions of the asymmetric synthesis, absolute configuration (AC) assignment methods, and systematic conformational analysis. We hope this work will enrich the knowledge of the stereochemistry of chiral 2-substituted chromanes.

Specific chiroptical sensing of cysteine via ultrasound-assisted formation of disulfide bonds in aqueous solution

Cysteine (Cys) can serve as a biomarker to indicate diseases or disorders, and its chiral sensing has attracted increasing attention. Herein, we established an ultrasound-facilitated chiral sensing method for Cys using 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl) and electronic circular dichroism (ECD) spectroscopy. The formation of chiral disulfide bonds induced degenerate exciton coupling between two NBD chromophores, resulting in intense Cotton effects (CEs) of the sensing product. The anisotropy factor (g) was linearly correlated with the enantiomeric excess of Cys across the visible region (400-500 nm), and other natural amino acids or biothiols did not interfere with the detection. This ultrasound-promoted efficient and specific chiral sensing method of Cys has potential for application in the diagnosis of related diseases.

Colorimetric determination of biothiols with AuNPs@MoS2 NSs as a peroxidase mimetic enzyme

The synthesis of AuNPs@MoS2 NSs was achieved and the sensing of biothiols was carried out using AuNPs@MoS2 NSs as enzyme mimics.

Synthesis of Ag(I)@Fum−Pr−Pyr−Benzimidazole and Its Optical and Catalytic Activities in Click Reactions

A hydrophilic fumed silica was used as a support and modified by benzimidazole scaffold, which can be chelate with silver as a highly selective and sensitive receptor to the successive detection of Ag+ ion. Fluorescence properties of Fum−Pr−Pyr−Benzimidazole were verified by the addition of various cations in an aqueous medium, and its high selectivity and sensitivity toward Ag+ ion was observed. Silver ion was placed onto the Fumed‐SiO2 to prepare Ag(I) @Fum−Pr−Pyr−Benzimidazole catalyst using in click chemistry. A number of characterization analyses were used, including FT‐IR, SEM, BET, and EDX, to prove that the Pr‐Pyr‐Benzimidazole and Ag (I) were homogeneously distributed on the fumed‐silica. EDX and SEM analysis were used to characterize the active component distribution.