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Six new compounds, globunones A-F (1-6), and two new flavonoids (7 and 8) together with nine known compounds (9-17) were isolated from the stems of Knema globularia. The chemical structures of 1-8 were elucidated by an analysis of their NMR and high-resolution electrospray ionization mass spectrometry data as well as by comparison with literature values. The absolute configurations were determined using time-dependent density functional theory electronic circular dichroism (TD-DFT-ECD). Globunones A-E (1-5) represent the initial combined structures of a flavan-3-ol core and a 1,4-benzoquinone core. Globunone F (6) is the first flavanone-type compound bearing a 2-(2,4-dihydroxyphenyl)-2-oxoethyl group found to date in Nature. Compounds 1-3 and 6-17 were tested for their yeast α-glucosidase inhibitory activity. All compounds tested (except for 13 and 14) showed potent inhibition toward α-glucosidase with IC50 values in the range 0.4-26.6 μM. Calodenin A (15) was the most active compound with an IC50 value of 0.4 μM (the positive control, acarbose, IC50 93.6 μM). A kinetic analysis of 15 revealed that it is a noncompetitive inhibitor with a Ki value of 3.4 μM.
Organoselenium compounds find versatile applications in organic synthesis, materials synthesis, and ligand chemistry. Organoselenium heterocycles are widely studied agents with diverse applications in various biological processes. This review highlights the recent progress in the synthesis of selenium heterocycles using diorganyl diselenides with keen attention on green synthetic approaches, scopes, C-H selanylation, the mechanisms of different reactions and insights into the formation of metal complexes. The C-H selanylation using diorganyl diselenides with different catalysts, bases, transition metals, iodine salts, NIS, hypervalent iodine, and other reagents is summarised. Finally, the diverse binding modes of bis(2/4-pyridyl)diselenide with different metal complexes are also summarised.
Herein, we report an efficient protocol for the synthesis of selenated tetracyclic indoloazulenes. The reaction of diorganyl diselenides with molecular iodine in dichloromethane leads to the in situ formation of organo selenenyl iodide. The synthesis of selenylated tetracyclic indoloazulenes through intramolecular cascade cyclization has been achieved via organo selenenyl iodide and bisindole at room temperature under metal-free conditions in good yields. All compounds were fully characterized by the FT-IR, HRMS, and 1H, 13C and 77Se NMR spectral data.
In this paper, we report iodine mediated in situ generation of R-Se-I and further their application towards the construction of pyrano[4,3-b]quinolin-1-one derivatives. The structural elaboration of 1-chloro-8-methyl-3-phenylbenzo[b][1,6]naphthyridine 6 was successfully achieved by Sonogashira, Suzuki coupling and dehalogenation reaction. Finally, among the synthesized compounds 4a, 5a, 5b, 6, 7a-7c were studied for photophysical properties including UV-absorption, fluorescence, and quantum yield study. The synthesized pyranoquinoline derivatives showed λmax, Fmax and Φf values in the range from 391-447 nm, 436-486 nm and 0.004-0.301, respectively in chloroform solvent.