S. Samundeeswari

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.

One-pot, green synthetic route for construction of coumarin C-4 bridged 2,6-dicyanoanilines and their photophysical study

ABSTRACT A highly selective and more efficient green protocol has been developed via a one-pot, three-component approach for the synthesis of coumarin 2,6-dicyanoanilines in aqueous ethanol. From the mechanism, two molecules of malanonitrile condensed with aldehyde and ketone resulted in the adducts, which on intramolecular cyclization via two new C-C bonds formed to afford the title compound. The present methodology offers simplified purification and environmentally benign conditions, avoids the use of toxic solvents, and gives excellent yield with high purity. All the synthesized compounds have been characterized by spectral analysis. Optical and thermal screening studies of all newly synthesized compounds showed excellent photophysical and thermal stability properties. GRAPHICAL ABSTRACT

Dual Fluorescence and Solvatochromic Study on 3-Acyl Coumarins

AbstractElectronic absorption and emission spectra of 3-acetyl coumarin, 3-(bromoacetyl) coumarin and 3-(di bromoacetyl) coumarin have been recorded at room temperature in thirteen solvents with different polarities. Both ground and excited state dipole moments have been calculated for both locally excited and charge transfer transitions by using the solvatochromic method. Excited state dipole moments of all the three compounds are higher than their ground state values. DFT calculations have been profound to estimate their ground and excited state dipole moments. The estimated change in dipole moment by the application of microscopic solvent polarity parameter and bulk solvent polarity methods are in close agreement. Concentration dependent dual fluorescence has been observed in the emission spectra of all the three compounds. Graphical AbstractDual fluorescence of 3-acetyl coumarin (I) in different solvents.

Design and synthesis of coumarin–imidazole hybrid and phenyl-imidazoloacrylates as potent antimicrobial and antiinflammatory agents

An improved one pot, multi-component synthesis of tri- and tetrasubstituted coumarin–imidazole hybrid has been synthesized at C4 position in good to excellent yield. The reaction was performed under various catalysts and optimization condition results obtained are satisfactory. Wherein, trisubstituted coumarin–imidazole hybrid compounds were converted into phenyl-imidazole acrylates. Further, all the newly synthesized compounds were screened for their antimicrobial activity against Gram-positive Bacillus flexus and Gram-negative Pseudomonas spp. bacterial strains and two strains of fungi studies having Scopulariopsis spp. and Aspergillus terreus organisms. Similarly, antiinflammatory activity of all the compounds was screened against MMP-2 and MMP-9. Both antimicrobial and antiinflammatory results are excellent, among all compounds, sodium acrylate compounds are quite promising against microbial strains and matrix metalloproteins (MMPs). All the isolated compounds were characterized by IR, NMR, and mass spectral analysis.Graphical abstract

An efficient and catalyst free methylthiolation of 4-(bromomethyl)-2H-chromen-2-ones with DMSO

GRAPHICAL ABSTRACT ABSTRACT The first simple, metal free, and efficient protocol has been established for the methylthiolation of structurally diverse 4-bromomethyl-2H-chromen-2-ones using dimethyl sulfoxide (DMSO) as methylthiolation source at higher temperature. The experimental method is highly economical and provides excellent yields of highly pure products which do not require further purification. All novel 4-[(methylthio)methyl]-2H-chromen-2-ones were characterized by 1H, 13C NMR, and single-crystal X-ray analysis.

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.

Crystal structure of 4-(4b,8a-di­hydro-9H-pyrido[3,4-b]indol-1-yl)-7-methyl-2H-chromen-2-one

In the title compound, the dihedral angle between the mean planes of the coumarin and β-carboline ring systems is 63.8 (2)°. In the crystal, molecules are linked via N—H⋯N hydrogen bonds, forming chains along the [010] direction.