Rapid and Efficient One-Pot Multicomponent Synthesis of Pyrano[3,2-c]chromene Derivatives,Catalyzed by a Deep Eutectic Solvent

Russian Journal of Organic Chemistry - A simple, efficient, and eco-friendly method for the construction of pyrano[3,2-c]chromene derivatives, involving a one-pot multicomponent condensation of...     

Chromatographic identification of “green capping agents” extracted from Nasturtium officinale (Brassicaceae) leaves for the synthesis of MoO3 nanoparticles

A low‐temperature, efficient and effective method was investigated for phytochemical hydroethanolic extraction of Nasturtium officinale (Brassicaceae). The phytocompounds of the selected plant leaves were identified by high‐performance liquid chromatography, gas chromatography with mass spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet‐visible spectroscopy. Acetic acid, d ‐alanine, octodrine, decanoic acid, and cyclohexylethylamine were the major phytocompounds identified in N. officinale leaves with high similarity match and spectral purity. The reducing and stabilizing potential of the extracted phytochemicals was demonstrated by synthesizing the metal oxide nanoparticles (MoO₃) by treating ammonium heptamolybdate tetrahydrate (H₄MO₇N₆O₂₄.4H₂O) aqueous complex with bioactive compounds of the leaves. The bio‐synthesized MoO₃ nanoparticles were characterized by ultraviolet‐visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, energy dispersive X‐ray spectroscopy, field emission‐scanning electron microscopy, and gas chromatography with mass spectroscopy. Gas chromatography‐mass spectroscopy identified acetic acid, d ‐alanine, and octodrine as stabilizing agents in the synthesis of MoO₃ nanoparticles.     

New insecticidal amides from petroleum ether extract of dried Piper nigrum L. whole fruits

The petroleum ether extract of dried ground whole fruits of Piper nigrum L. afforded 20 compounds (1-20) including two new insecticidal amides named as pipnoohine (1), and pipyahyine (2), seven reported for the first time from this plant (12, 13, 15-17, 19, 20), and eleven known compounds (3-11, 14, 18). The structure of 1 has been elucidated as (2E,4E,12Z)-N-(4-methylpentyl)octadeca-2,4,12-trienamide and that of 2 as (2E,4E,11E)-12-(benzo[1,3]dioxol-5-yl)-N-(3-methylbutyl)dodeca-2,4,11-trien-amide through extensive ID-, 2D-NMR spectral studies and chemical reactions. The known compounds have been identified through comparison of their spectral data with those reported in literature. 1 and 2 exhibited toxicity at 35.0 and 30.0 ppm respectively against fourth instar larvae of Aedes aegypti L. by WHO method.     

Metachronal propulsion of non-Newtonian viscoelastic mucus in an axisymmetric tube with ciliated walls

Cilia-induced flow of viscoelastic mucus through an idealized two-dimensional model of the human trachea is presented.The cilia motion is simulated by a metachronal wave pattern which enables the mobilization of highly viscous mucus even at nonzero Reynolds numbers.The viscoelastic mucus is analyzed with the upper convected Maxwell viscoelastic formulation which features a relaxation time and accurately captures normal stress generation in shear flows.The governing equations are transformed from fixed to wave(laboratory)frame with appropriate variables and resulting differential equations are perturbed about wave number.The trachea is treated as an axisymmetric ciliated tube.Radial and axial distributions in axial velocity are calculated via the regular perturbation method and pressure rise is computed with numerical integration using symbolic software MATHEMATICA^‘TM’.The influence of selected parameters which is cilia length,and Maxwell viscoelastic material parameter i.e.relaxation time for prescribed values of wave number are visualized graphically.Pressure rise is observed to increase considerably with elevation in both cilia length and relaxation time whereas the axial velocity is markedly decelerated.The simulations provide some insight into viscous-dominated cilia propulsion of rheological mucus and also serve as a benchmark for more advanced modeling.     

Synthesis,Characterization and Crystal Structure of Some Novel 1‐Aryl‐2‐Thioxo‐2,3‐Dihydro‐1H‐Quinazolin‐4‐Ones

The base catalyzed intramolecular nucleophilic cyclization of 1‐(2‐haloaroyl)‐3‐aryl thioureas ( 1a‐i ), in the presence of DMF afforded the 1‐aryl‐2‐thioxo‐2,3‐dihydro‐1H‐quinazolin‐4‐ones ( 2a‐i ). The structures were confirmed by spectroscopic data, elemental analyses and in case of the 2c by single crystal X‐ray diffraction data. The mechanistic studies support an intramolecular nucleophilic substitution (S_NAr mechanism) rather than intramolecular aromatic substitution (S_RN1 mechanism).     

Synthesis and antimicrobial activity of some novel 2-(substituted fluorobenzoylimino)-3-(substituted fluorophenyl)-4-methyl-1,3-thiazolines

The synthesis of several 2-(substituted fluorobenzoylimino)-3-(substituted fluorophenyl)-4-methyl-1,3-thiazolines (2a-t) was carried out by base-catalyzed cyclization of corresponding 1-(fluorobenzoyl)-3-(fluorophenyl)thioureas (1a-t) with 2-bromoacetone in aqueous medium. The structures of the synthesized compounds were confirmed by spectral and elemental analysis. All synthesized compounds were evaluated for in vitro antibacterial activity using Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa). The minimum inhibitory concentration (MIC) was determined for the most active compounds. In vitro antifungal activity was also determined against the five fungal species (Rhizopus oryzae, Fusarium oxysporum, Aspergillus terreus, A. niger and A. fumigatus).     

Specific Deuteration in Patuletin and Related Flavonoids via Keto–Enol Tautomerism: Solvent‐ and Temperature‐Dependent 1H‐NMR Studies

An H/D exchange process in patuletin ( 1 ) and its derivatives in D‐donor solvents (e.g., CF₃COOD), which occurs regioselectively at C(8) was observed for the first time during NMR studies. The effect of substituents and temperature on the deuteration of various flavonoids (see Fig. 1) which include apigenin, chrysin, galangin, kaempferol, luteolin, morin, myricetin, patuletin, patulitrin, and quercetin, as well as derivatives of patuletin was examined extensively under NMR conditions. The rate constant of deuteration at C(8) of patuletin ( 1 ) and two flavones, luteolin ( 3 ) and apigenin ( 12 ), was also determined in CF₃COOD. The D‐atom was introduced into the flavonoids via a keto–enol tautomerism (Scheme 1). During these studies, monodeuterated patuletin was also obtained as a new compound. The examined flavonoids have been reported to possess significant pharmacological activities, and their deuterated derivatives would be of importance for the identification and quantification of these compounds in biological matrices.     

Structure activity relationship of bergenin,p-hydroxybenzoyl bergenin, 11-O-galloylbergenin as potent antioxidant and urease inhibitor isolated from Bergenia ligulata

Ethanol extract of the aerial parts of Bergenia ligulata was subjected to solvent–solvent separation followed by various chromatographic techniques that lead to isolation of bergenine (1), p-hydroxybenzoyl bergenin (2), 11-O-galloylbergenin (3) and methyl gallate (4) as major constituents. Ethyl acetate fraction showed a dose-dependent urease inhibitory pattern with IC₅₀ value of 54μg/mL. Structures of compounds 1 and 3 were established by XRD and 2, 4 by NMR. All these compounds were subjected to DPPH scavenging activity, reducing power assay and urease inhibitory activity. The EC₅₀ 7.45 ± 0.2 μg/mL and 5.39 ± 0.28 μg/mL values in terms of antioxidant and reducing power, respectively, were less for 3. Compounds 1–3 showed moderate to significant urease inhibitory potential with IC₅₀ 57.1 ± 0.7, IC₅₀ 48.4 ± 0.3 and 38.6 ± 1.5. Antioxidant activities and urease inhibitory potential were investigated and compound 3 was found to be the most active.     

Separation of isorhamnetin 3‐sulphate and astragalin from Flaveria bidentis (L.) Kuntze using macroporous resin and followed by high‐speed countercurrent chromatography

D4020 resin offered the best dynamic adsorption and desorption capacity for total flavonoids based on the research results from ten kinds of macroporous resin. A column packed with D4020 resin was used to optimize the separation of total flavonoids from Flaveria bidentis (L.) Kuntze extracts. The content of flavonoids in the product was increased from 4.3 to 30.1% with a recovery yield of 90%. After the treatment with gradient elution on D4020 resin, the contents of isorhamnetin 3‐sulfate and astragalin were increased from 0.49 to 8.70% with a recovery yield of 74.1% and 1.16 to 30.8%, with a recovery yield of 92.2%, respectively. Further purification was carried out by one‐run high‐speed countercurrent chromatography yielding 4.5 mg of isorhamnetin 3‐sulfate at a high purity of 96.48% and yielding 24.4 mg of astragalin at a high purity of over 98.46%.