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61.
The red-shift of furocoumarin action spectra, compared with their absorption spectra, has been investigated. An action spectrum for 8-methoxypsoralen (8-MOP) monoadduct formation in the yeast Candida albicans has been determined. The yeast cells were initially exposed to sublethal doses of monochromatic UVA at different wavelengths. Monoadduct formation was monitored by growth inhibition induced, after washing out any unbound 8-MOP, by re-irradiation with a constant second (non-lethal) dose of 330 nm radiation. A comparison between this action spectrum and the absorption spectrum of the dark complex of 8-MOP and DNA was made. In addition, the action spectra of monoadduct formation of five monofunctional compounds including a coumarin derivative have been determined. These action spectra were compared with their respective DNA dark complex absorption spectra. In general, the peaks of the furocoumarin DNA dark complexes show a red-shift when compared with the free furocoumarin molecule and the action spectra show peaks which correspond with the peaks of the dark complexes. Such data indicate that the DNA dark complex is the chromophore for growth inhibition in yeast rather than the free furocoumarin. The similarity of the 8-MOP monoadduct formation action spectrum and 8-MOP action spectra suggests that spectral dependence for the photobiological effects (including the red-shift) is dependent on monoadduct formation rather than, as previously suggested by several authors, crosslink formation. The action spectrum for the coumarin derivative 4-methyl N-ethylpyrrolo (3,2-g) coumarin (PCNEt) correlated well with the free molecule absorption spectrum rather than DNA dark complex indicating that the free molecule is the chromophore.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
62.
Dr. Abdul Khayum Mohammed Dr. Jésus Raya Ajmal Pandikassala Dr. Matthew A. Addicoat Safa Gaber Mohamed Aslam Dr. Liaqat Ali Dr. Sreekumar Kurungot Prof. Dinesh Shetty 《Angewandte Chemie (International ed. in English)》2023,62(29):e202304313
Hydrogen-bonded organic frameworks (HOFs) are ordered supramolecular solid structures, however, nothing much explored as centimetre-scale self-standing films. The fabrication of such crystals comprising self-supported films is challenging due to the limited flexibility and interaction of the crystals, and therefore studies on two-dimensional macrostructures of HOFs are limited to external supports. Herein, we introduce a novel chemical gradient strategy to fabricate a crystal-deposited HOF film on an in situ-formed covalent organic polymer film (Tam-Bdca-CGHOF). The fabricated film showed versatility in chemical bonding along its thickness from covalent to hydrogen-bonded network. The kinetic-controlled Tam-Bdca-CGHOF showed enhanced proton conductivity (8.3×10−5 S cm−1) compared to its rapid kinetic analogue, Tam-Bdca-COP (2.1×10−5 S cm−1), which signifies the advantage of bonding-engineering in the same system. 相似文献
63.
K. D. Safa A. Bahadori S. Tofangdarzadeh M. H. Nasirtabrizi 《Journal of the Iranian Chemical Society》2008,5(1):37-47
The new bulky organosilicon compound HC(Me2SiCH2CH2CH2OCH2CycloCHCH2O)3 was synthesized by hydrosilylation of tris(dimethylsilyl)methane (HMe2Si)3CH and allyl glycidyl ether (AGE) in the presence of H2PtCl6 as a catalyst. Polysiloxanes containing 3-(2,3-epoxypropoxy)propyl and chloromethylphenethyl groups were synthesized by hydrosilylation of AGE and chloromethyl styrene (CMS) with hydrogen-containing polymethylsiloxane (PMHS). Both types of polymers could be modified by incorporation of the highly sterically-demanding tris(trimethylsilyl)methyl [trisyl = (Me3Si)3C] substituent. The trisyl (Tsi) groups were attached to the obtained polymers as side chains by reacting excess trisyl lithium with benzyl chloride and epoxy groups. The epoxy groups possess a higher reactivity for TsiLi than the chloromethyl groups. The ring opening reaction between the epoxy groups and TsiLi is fast. The modification increases the rigidity of the polymers as shown by differential scanning calorimetry analysis. The incorporation of the Tsi groups into the polymer structure creates macromolecules of novel architecture with potential use as membranes for fluid separation. All the resulting polymers were characterized by FT-IR and 1H NMR spectroscopy. 相似文献
64.
A highly efficient and environmentally friendly one-pot procedure for the synthesis of 1,2,3-triazoles by 1,3-dipolar cycloaddition of benzyl halides, terminal alkynes, and sodium azide over LaCuxMn1-xO3 perovskite oxides was developed. LaCu0.7Mn0.3O3 was found to be active with low catalyst loading under ultrasonic irradiation in aqueous media. The reaction was performed efficiently in the presence of the nanocatalyst in the absence of any additive or base with a noticeable reduction in the reaction time. The catalyst could be recycled and reused at least five times without any significant effect on the results of the reaction. Moreover, a series of novel organosilicon-sulfur substituted 1,2,3-triazole derivatives was synthesized using carbon disulfide and tris(trimethylsilyl)methylithium. 相似文献
65.
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67.
A series of 8-azacoumarin, naphthyridine, and dioxazphenalene derivatives bearing conjugated moieties were intended and prepared by a concise and smooth approach using grinding and ultrasonic irradiation. A sustainable one pot reactions have emerged and progressed smoothly as an efficient and eco-safe methods in solvent less organic synthesis. The desired products were obtained in high yields, and the structures of all products were established on the basis of spectroscopic data and elemental analysis. Using the density functional theory (DFT) realized the electronic and structure characterization of synthesized azacoumarin. These heterocyclic compounds are chemically stable and are tested as antioxidants. Antioxidant potential was assessed using ABTS, and anti-hemolytic activity was evaluated by induced peroxide hemolysis. They gave good antioxidant results that showed potency ranging from good azacoumarin analogues 8 , 9 , 13 , 17 , and 20 , among compounds, showed much potency than that of commercial ascorbic acid. 相似文献
68.
Mohsen K.A. Regal Safa S. Shaban Souad A. El-Metwally 《Journal of heterocyclic chemistry》2020,57(3):1368-1378
PTC reaction of coumarin derivative 1 with alkyl halides afforded C4 oxygen alkylation products 2a-d in appreciative yield, whereas with phenyl isothiocyanate gives the C3 addition product 4 ; also, one-pot three-component PTC reaction was investigated. Treatment of coumarin 1 with aromatic aldehydes in different molar ratios gives 3-arylidene derivatives 7a,b and the dicoumarol derivatives 8a,b . Pyrano chromene 9 and pyrano pyridine 10 were obtained by reaction of arylidene 7a with ethyl acetoacetate through Michael cycloaddition reaction. The stability of pyrone ring in 3-arylidene 7 and dicoumarol 8 towards different nucleophilic reagents under reflux and/or fusion conditions has been studied by the action of hydrazine hydrate, ammonium acetate, methyl amine, and p-toluidine afforded compounds 11 and 13a-c . The antimicrobial activity of some synthesized compounds has been investigated. 相似文献
69.
AbstractThe one-pot synthesis of tetrasubstituted imidazoles by use of a series of LaxSr1 ? xFeyCo1 ? yO3 perovskites as catalysts is described. The La0.8Sr0.2Fe0.34Co0.66O3 nanocatalyst had the greatest activity in the heterogeneous cyclocondensation of an aldehyde, benzil, ammonium acetate, and a primary aromatic amine in water under ultrasonic irradiation. Some of the derivatives generated during this work were utilized as substrates for the synthesis in good yields of novel multifunctional tetrasubstituted imidazoles with Me3Si, C=S, and SH groups, via nucleophilic attack of tris(trimethylsilyl)methyllithium (TsiLi) at the carbon of carbon disulphide. 相似文献
70.
Kazem D. Safa Afsaneh Zeinolabedini Hassan Abbasi Reza Teimuri-Mofrad 《Journal of the Iranian Chemical Society》2013,10(3):447-452
A three-component efficient procedure is described for the synthesis of α-aminonitriles containing bis(trimethylsilyl)ethenyl groups from 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1), aromatic amines and trimethylsilyl cyanide (TMSCN). Reactions have been studied in the presence of various Lewis acids as catalysts or in ionic liquids under mild conditions. Compound (1) was obtained via Peterson olefination of terephthaldehyde with tris(trimethylsilyl)methyllithium, (Me3Si)3CLi, in THF at 0 °C. 相似文献