Green, unexpected synthesis of bis-coumarin derivatives as potent anti-bacterial and anti-inflammatory agents.

A green and efficient protocol has been developed and a series of coumarin based pyrano[3,2-c]chromene derivatives (2) have been synthesized using multi-component reaction (MCR) approach. Unexpected 3-coumarinyl-3-pyrazolylpropanoic acids (3) and C4-C4 chromenes (5) have been isolated instead of expected product 4 by the reaction of compound (2) in formic acid at 90 °C for about 4-5 h and at 130 °C for about 8-10 h respectively. Further, C4-C4chromenes (5) formation was confirmed by intramolecular cyclization of compounds (3). These compounds were screened for their biological activities and most of them exhibited promising antibacterial activity. The anti-inflammatory assay was evaluated against HRBC membrane stabilization method and the compounds exhibit excellent anti-inflammatory activity. Molecular docking study has been performed for all the synthesized compounds with Klebsiella pneumoni aeacetolactate synthase and results obtained are quite promising.

Synthesis of Naked-eye Detectable Fluorescent 2H-chromen-2-One 2, 6-Dicyanoanilines: Effect of Substituents and pH on Its Luminous Behavior.

A variety of new coumarin derivatives containing C-4 bridged 2,6-dicyanoanilines (4a-4d) were synthesized via multicomponent one pot approach. These novel sensors were characterized by spectral analysis and a series of pH sensing fluorescence studies were performed, the results indicating that the sensors are highly selective and more effective at various pH. The fluorescence colour changes at different pH could be directly detected by naked eyes.

3,4-Dihydropyrimidinone-coumarin analogues as a new class of selective agent against S. aureus: Synthesis, biological evaluation and molecular modelling study.

Bacterial infections are increasingly difficult to combat as bacteria evolve resistance to antibiotic drugs and have severely compromised the arsenal of antibiotic drugs. On the other hand matrix metalloproteinases (MMPs) play a fundamental role in inflammation and extracellular matrix degradation in physiological and pathological conditions. In search of potent antibiotic, taking coumarin and dihydropyrimidinone as lead compound, a green, eco-friendly and efficient protocol has been developed and synthesized the dihydropyrimidin-2(1H)-one/thione derivatives of coumarin 3/4 from substituted 4-formylcoumarins 2 and ethylacetoacetate using urea/thiourea in the presence of catalytic amount of ceric ammonium nitrate is reported. All the synthesized compounds were evaluated for their antibacterial activity against four bacterial strains by broth dilution method. The tested compounds have exhibited promising in vitro potency with low MIC values against the drug susceptive S. aureus strain with low MIC values ranging from 0.2 to 6.25µg/mL. The in vivo anti-inflammatory potency of 3a-e and 4a-e by gelatin zymography is comparable to that of tetracycline. Molecular docking study performed for all the synthesized compounds with S. aureus DNA gyrase and results obtained were quite promising.

Synthesis, Characterization and Photophysical Studies of Tricoumarin-Pyridines.

A series of novel tricoumarin-pyridines have been synthesized by the reaction of 4-formyl coumarins and substituted 3-acetylcoumarin with ammonium acetate for the application in organic electronics as well as fluorescent dyes. The structures of all new compounds were confirmed and characterized by IR, 1H NMR and ESI-Mass analysis. All the important photo physical prerequisites for organic electronic application such as strong and broad optical absorption, thermal stability were determined for the synthesized molecules. Optical properties were studied by UV-Vis absorption and fluorescence spectroscopy. Optical band gaps of the tricoumarin-pyridines were found to be 2.72-3.10 eV as calculated from their onset absorption edge. The tricoumarin-pyridines were thermally stable up to 290-370 °C as determined by thermogravimetric analysis (TGA). Photophysical studies indicate the synthesized materials are promising candidates for organic electronic applications.