Modular Access to meta-Substituted Benzenes via Mo-Catalyzed Intermolecular Deoxygenative Benzene Formation.

The substituted benzene derivatives are essential to organic synthesis, medicinal chemistry, and material science. However, the 1,3-di- and 1,3,5-trisubstituted benzenes are far less prevalent in small-molecule drugs than other substitution patterns, likely due to the lack of robust, efficient, and convenient synthetic methods. Here, we report a Mo-catalyzed intermolecular deoxygenative benzene-forming reaction of readily available ynones and allylic amines. A wide range of unsymmetric and unfunctionalized 1,3-di- and 1,3,5-trisubstituted benzenes were obtained in up to 88% yield by using a commercially available molybdenum catalyst. The synthetic potential of the method was further illustrated by synthetic transformations, a scale-up synthesis, and derivatization of bioactive molecules. Preliminary mechanistic studies suggested that this benzene-forming process might proceed through a Mo-catalyzed aza-Michael addition/[1,5]-hydride shift/cyclization/aromatization cascade. This strategy not only provided a facile, robust, and modular approach to various meta-substituted benzene derivatives but also demonstrated the potential of molybdenum catalysis in the challenging intermolecular deoxygenative cross-coupling reactions.

Catalytic Asymmetric Deoxygenative Cyclopropanation Reactions by a Chiral Salen-Mo Catalyst.

The catalytic asymmetric cyclopropanation reaction of alkenes with diazo compounds is a direct and powerful method to construct chiral cyclopropanes that are essential to drug discovery. However, diazo compounds are potentially explosive and often require hazardous reagents for their preparation. Here, we report on the use of 1,2-dicarbonyl compounds as safe and readily available surrogates for diazo compounds in the direct catalytic asymmetric deoxygenative cyclopropanation reaction. Enabled by a class of simple and readily accessible chiral salen-Mo catalysts, the reaction proceeded with generally good enantioselectivities and yields toward a wide range of substrates (80 examples). Preliminary mechanistic studies suggested that the proposed µ-oxo bridged dinuclear Mo(III)-species was the catalytically active species. This strategy not only provides a promising route for the synthesis of chiral cyclopropanes but also opens a new window for the potential applications of chiral salen-Mo complexes in asymmetric catalysis.

Rapid one-pot isothermal amplification reassembled of fluorescent RNA aptamer for SARS-CoV-2 detection.

The outbreak of SARS-CoV-2 poses a serious threat to human life and health. A rapid nucleic acid tests can effectively curb the spread of the disease. With the advantages of fluorescent RNA aptamers, low background and high sensitivity. A variety of fluorescent RNA aptamer sensors have been developed for the detection of nucleic acid. Here, we report a hypersensitive detection platform in which SARS-CoV-2 initiates RTF-EXPAR to amplify trigger fragments. This activation leads to the reassembled of the SRB2 fluorescent RNA aptamer, restoring its secondary structure for SR-DN binding and turn-on fluorescence. The platform completes the assay in 30 min and all reactions occur in one tube. The detection limit is as low as 116 aM. Significantly, the platform's quantitative analyses were almost identical to qPCR results in simulated tests of positive samples. In conclusion, the platform is sensitive, accurate and provides a new protocol for point-of-care testing of viruses.

Pharmacokinetic study of salvianolic acid A in rat after intravenous administration of Danshen injection.

In order to research the pharmacokinetics of salvianolic acid A (SalA), a herbal ingredient isolated from Salvia miltiorrhiza Bunge, after intravenous administration to rats, a specific and accurate high-performance liquid chromatography (HPLC) was developed. The assay procedure involved simple liquid-liquid extraction of SalA and internal standard (IS, ethyl-p-hydroxybenzoate) from plasma into ethyl acetate. The organic layer was separated and evaporated under reduced pressure at 40 degrees C. The residue was reconstituted in the mobile phase and analyzed on an Inertsil C8 column, monitored at 285 nm. The mobile phase, which consisted of methanol-acetonitrile-water-formic acid (10:20:70:0.4, by vol), was used at a flow rate of 1.0 mL/min. The ratio of the peak area of the analyte to IS was applied to quantify the plasma samples. The standard curve for SalA was linear (r2 = 0.9999) in the concentration range of 0.75-150 microg/mL. The limit of quantitation (LOQ) of SalA was 0.75 microg/mL. The intra- and inter-day precisions (RSD) of the quality control (QC) samples were in the ranges of 2.17-3.29 and 1.24-5.28%, respectively. Accuracy in the measurement of QC samples ranged from 94.7 to 101.1%. This method was validated for specificity, accuracy and precision and was successfully applied to the pharmacokinetic study of SalA in rat plasma after intravenous administration of Danshen injection.