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Selectivities in the Microwave-Assisted Organic Reactions
Published in Banik Bimal Krishna, Bandyopadhyay Debasish, Advances in Microwave Chemistry, 2018
Four years later, they studied the tandem Knoeveagel and heteroatom-Diels–Alder reactions of 4-hydroxycoumarin and substituted 5-(3-methyl-2-butenylthio)pyrazole-4-carbaldehydes. The reactions produced coumarin derivatives and chromone derivatives in 54 ~ 68% yields with ratios of 51:49 ~ 59:41 under refluxing in ethanol for 4.5 ~ 10 hours under conventional heating, while the reactions gave rise to the corresponding products in 72 ~ 85% yields with ratios of 70:30 ~ 76:24 under microwave irradiation (800 W) for 1 ~ 4.5 minutes. When they absorbed the starting materials on the Montmorillonite K-10 and irradiated with microwave (800 W) for 23 ~ 65 seconds under solvent-free conditions, the corresponding products were obtained in 82 ~ 91% yields with ratios of 89:11 ~ 95:5. The selectivities, yields, and efficiencies were improved obviously (Scheme 6.5) [12].
Bioactive Compounds in agricultural and Food production Waste
Published in Quan V. Vuong, Utilisation of Bioactive Compounds from Agricultural and Food Waste, 2017
Nenad Naumovski, Senaka Ranadheera, Jackson Thomas, Ekavi Georgousopoulou, Duane Mel lor
Glycosides are organic compounds usually found in plants and may contain phenol, alcohol or sulphur compounds within their structure. They are characterized by a sugar portion or moiety attached by a special bond (mostly a glycosidic bond) to one or non-sugar functional compounds. Many plants store chemicals in the form of inactive glycosides, which can be activated by enzyme hydrolysis, causing the sugar part to be detached and making the chemical available for use (Brito-Arias 2007, Kabera et al. 2014). These plant glycosides are extremely diverse and mostly categorized as prodrugs since they remain inactive until they are hydrolyzed in the large intestine, leading to the release of the aglycone or the non-sugar portion, which is the right active constituent (Kabera et al. 2014). Glycosides are heterogeneous in structure and their classification is based on the nature of aglycone, which can be a wide range of molecular types, including phenols, quinines, terpenes and steroids (Kabera et al. 2014). Certain classifications are based on the therapeutic properties of glycosides, which can be further categorized into different groups, such as cardiac/ steroidal, flavonoid, saponin, anthraquinone, cyanophore, isothiocyanate, alcohol, lactone, phenolic, coumarin, chromone and iridoid glycosides. Glycosides can also be categorized into four major groups based on the atoms involved in glycosidic linkage or the type of glycosidic bond: C-glycoside (when sugar moiety is lined with carbon atom), O-glycoside (with oxygen), S-glycoside (with sulphur) and N-glycoside (with nitrogen) (Brito-Arias 2007).
Green Chemistry and Green Catalysts
Published in Ahindra Nag, Greener Synthesis of Organic Compounds, Drugs and Natural Products, 2022
Ahindra Nag, Himadri Sekhar Maity
Pyran derivatives represent the key moiety of various naturally occurring and synthetic products such as benzopyrans, coumarins, flavonoids, xanthones, chromone, sugars and naphthoquinones displaying diverse medicinal and biological activities.41,44
New thiourea and urea derivatives containing trifluoromethyl- and bis-triflouromethyl-4H-chromen-3-yl substituents
Published in Molecular Physics, 2019
C. D. Alcívar León, G. A. Echeverría, O. E. Piro, S. E. Ulic, J. L. Jios, C. A. Luna Tapia, M. F. Mera Guzmán
In vitro antimicrobial activity of the novel chromone derivatives 1 and 2 was investigated against five bacteria strains (Pseudomonas aeruginosa (27,853), Escherichia coli (25,922), Salmonella typhimurium (14,028), Klebsiella pneumoniae (10,031) and Staphylococcus aureus (292,113). The antibacterial activity was carried out by measuring the inhibition zone using the agar diffusion technique (Kirby–Bauer method) [31]. The compounds were dissolved in dimethylsulfoxide (DMSO) to a concentration of 0.01 mg/mL and Gentamicin discs were used as a standard antibiotic (10 µg). In nutrient broth medium, 24 h fresh bacterial cultures were prepared. Bacterial culture McFarland 0.5% barium sulphate solution was used to compare the turbidity and Mueller-Hinton agar petri plates were prepared to perform the antibacterial assay. Aseptic cotton swabs and agar plates were used to form a bacterial lawn. 25 µL of test solution were poured into respective discs using a micropipette, and the petri plates were incubated at 37°C for 24 h. The zones of inhibition (mm) were calculated and compared with the standard drug (Gentamicin).
Efficient synthesis of 3-hydroxy chromones via oxidative cyclization mediated by lipase
Published in Green Chemistry Letters and Reviews, 2022
Jiapeng Li, Yue Yu, Yaning Xu, Fengxi Li, Yuqi Liu, Yifei Sun, Chunyu Wang, Peng Chen, Lei Wang
Chromones are privileged structural skeleton in flavonoid natural products and functional molecules with a vast range of applications in clinical medicine and functional materials (1, 2). Among all chromones, 3-hydroxy-chromnone (3-HC) and its derivatives represent an important class, which exhibits fluorescent properties due to the excited state of the intramolecular proton transfer (ESIPT) process (3). The noticeable spectral properties make 3-HC derivatives a useful fluorescent sensor of normal and supercritical liquids, lipid membranes, DNA, and proteins (4–6). Therefore, the synthesis of 3-HC derivatives has drawn great attention among organic chemists over the last few decades.
Synthesis, spectral, magnetic, DFT calculations, antimicrobial studies and phenoxazinone synthase biomimetic catalytic activity of new binary and ternary Cu(II), Ni(II) and Co(II) complexes of a tridentate ONO hydrazone ligand
Published in Inorganic and Nano-Metal Chemistry, 2020
Magdy Shebl, Akila A. Saleh, Saied M. E. Khalil, Magdah Dawy, Amira A. M. Ali
Synthesis and characterization of compounds containing chromone moiety have attracted a special interest due to importance of these compounds and their variable applications including antimicrobial, antioxidant, antitumor, anti-inflammatory, and anti-HIV properties in addition to other potential biological and pharmaceutical properties.[11–17]