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701.
Ugo Azzena Giovanna Dettori Ilaria Mascia Luisa Pisano Mario Pittalis 《Tetrahedron》2007,63(48):11998-12006
The regioselectivity of the reductive cleavage of 3,4,5-trimethoxybenzyl methyl ether strongly depends on the alkali metal employed as a reducing agent and solvent effects. Reactions run using Na as a reducing agent led to aromatic C(4)-O bond cleavage, whilst reductions run in the presence of Na/15-crown-5, or using Li as a reducing agent, led to highly regioselective benzylic C-O bond cleavage. This regioselectivity turnaround is discussed in terms of major solvent effects affecting the fragmentation paths of a common reaction intermediate. Synthetic applications of these findings led to the synthesis of biologically active compounds, like 2,5-dialkyl-substituted resorcinols, or 1-(3,4,5-trimethoxyphenyl)-2-arylethanes structurally related to combretastatin. 相似文献
702.
Giovanna Pressi Roberto Dal Toso Renzo Dal Monte Giovanni Carturan 《Journal of Sol-Gel Science and Technology》2003,26(1-3):1189-1193
Ajuga reptans cells are cultivated and used for production of invertase. These plant cells are immobilized by a sol-gel SiO2 membrane, which is built up directly on the cell surface by exposure to a gaseous flow of silicon alcoxide precursors. The immobilization modifies the metabolic activity of cells, resulting in a 40-fold increase in invertase production with respect of free cells. Results concerning total release of proteins, cell growth and produced invertase activity are discussed, considering the absence of breeding, induced by SiO2 immobilization, the prominent factor promoting the observed exceptional increase in invertase productivity. 相似文献
703.
Tripodo G Pitarresi G Palumbo FS Craparo EF Giammona G 《Macromolecular bioscience》2005,5(11):1074-1084
In this work, INU, a natural polysaccharide, has been chemically modified in order to obtain new photocrosslinkable derivatives. To reach this goal, INU has been derivatized with MA thus obtaining four samples (INU-MA derivatives) as a function of the temperature and time of reaction. An aqueous solution of the derivative INU-MA1 was irradiated by using a UV lamp with an emission range from 250 to 364 nm and without using photoinitiators. The obtained hydrogel showed a remarkable water affinity but it underwent a partial degradation in simulated gastric fluid. To overcome this drawback, INU-MA1 was derivatized with SA thus obtaining the INU-MA1-SA derivative designed to produce a hydrogel showing a low swelling and an increased chemical stability in acidic medium. Ibuprofen, as a model drug, was loaded by soaking into INU-MA1 and INU-MA1-SA hydrogels and its release from these matrices was evaluated in simulated gastrointestinal fluids. INU-MA1 hydrogel showed the ability to quickly release the entrapped drug thus indicating its potential as a matrix for an oral formulation. INU-MA1-SA hydrogel showed a pH-responsive drug delivery. Therefore it is a promising candidate for controlled drug release in the intestinal tract. 相似文献
704.
Md Azizul Haque Ksenia Morozova Nathan Lawrence Giovanna Ferrentino Matteo Scampicchio 《Electroanalysis》2021,33(1):23-28
This work investigates the reactivity of individual antioxidants with the free radicals generated by 2,2′-azobis(isobutironitrile) (AIBN). The consumption of antioxidants was followed by cyclic voltammetry. The fitting of such decay with a kinetic model yielded the rate constant of radical formation and the rate constant of radical inhibition exerted by each antioxidant. The antioxidant efficiency was defined as the ratio between and . The following ranking of antioxidants was obtained: α-tocopherol≫catechin≫retinyl acetate≫hydroxytyrosol≫oleuropein≫caffeic acid. Overall, the approach shows the utility of cyclic voltammetry to investigate the kinetic rates at which antioxidants react with radicals. 相似文献
705.
Giovanni Coni Marcella Massacesi Gustavo Ponticelli Giovanna Puggioni Costantino Putzolu 《Transition Metal Chemistry》1987,12(4):379-381
Summary Palladium(II) and platinum(II) complexes [MLX2], where L=2-(4-methyl-2-pyridyl)benzimidazole (mpbi), 2-(4-methyl-2-pyridyl)benzoxazole (mpbo), 2-(4-methyl-2-quinolyl)benzoxazole (mpbo), 2-(4-methyl-8-quinolyl)benzoxazole (mq'bo), X=Cl. Br, together with M(mqbo)2Br2 and Pt2(mpbt)Cl4, where mpbt=2-(4-methyl-2-pyridyl)benzthiazole, have been synthesized and characterized by conductivity and magnetic measurements as well as by i.r. and electronic spectra. The ligands are bidentate chelates through the pyridine or quinoline and isoxazole or imidazole nitrogen atoms. The [MLX2] derivatives arecis, square planar. 相似文献
706.
Caracciolo G Piotto S Bombelli C Caminiti R Mancini G 《Langmuir : the ACS journal of surfaces and colloids》2005,21(20):9137-9142
Energy dispersion X-ray diffraction (EDXD) was applied to investigate the structure of partly dehydrated mixed films formed by the phospholipid dimyristoyl phosphatidylcoline (DMPC) and any of the three diastereomers of the dicationic gemini surfactant (2S,3S)-2,3-dimethoxy-1,4-bis(N-hexadecyl-N,N-dimethylammonium) butane dibromide. As the surfactant to lipid molar ratio (R(S/L)) increases, the gemini monotonically solubilizes the lipid bilayer promoting the formation of a cubic phase of space group Pmn segregating from the residual lamellar phase of the lipid. Finally, at R(S/)(L) = 1, the phase transition is complete. The mixed film at the highest surfactant to lipid molar ratio (R(S/L) = 2.3) was hydrated by a vapor saturated atmosphere. At full hydration, a cubic to lamellar phase transition occurs. Coarse grain dynamic investigations, carried out as a function of both the surfactant to lipid molar ratio and the number of water molecules for amphiphile unit, allowed us to elucidate the structure of the emerging cubic phase and the hydration-induced structural pathway of the cubic to lamellar phase transition observed by EDXD. 相似文献
707.
Fabrizio Melani Lucia Cecchi Giovanna Palazzino Guido Filacchioni 《Journal of heterocyclic chemistry》1985,22(4):1109-1112
The synthesis of pyrazolo[4,5-c][1]benzazepin-10-ones 10 and 13 and pyrazolo[4,3-c][1]benzazepin-10-ones 11 and 12 is reported. The structure of compounds 10-13 and that of their parent compounds 2-5 ensues from a 13C nmr study. 相似文献
708.
Adsorbed polymers are widely used to suppress electroosmotic flow (EOF) in capillary electrophoresis (CE). Polymeric coatings, physisorbed onto the surface of the capillary wall, are often unstable under harsh conditions. This can be attributed to the reversible nature of the coating which becomes apparent when the adsorbed layer competes with a second species in the electrophoresis buffer solution for attachment/interaction with the capillary surface. In an effort to overcome the problem of coating instability, trimethoxysilane-modified polydimethylacrylamide was synthesized. This copolymer rapidly adsorbs on the wall from ultradilute aqueous solutions. After incubation at a temperature of 60 degrees C silyl groups, which extend from the polymer backbone, form condensation bonds with the silanols on the capillary surface. This enables subsequent formation of strong covalent bonds between the copolymer and the capillary wall. In this research, we establish that physisorption of polymer chains to the surface is essential for close alignment of surface and polymer silane groups which facilitates the formation of covalent bonds. 相似文献
709.
Begala M Forni A Delogu G Podda G Prati F Torre G Tubaro M 《Rapid communications in mass spectrometry : RCM》2004,18(1):59-66
A series of cis- and trans-isomeric aziridines has been studied under electron impact (EI) and electrospray ionization (ESI) conditions. The fragmentation patterns of the examined compounds have been elucidated by means of sequential product ion fragmentation experiments (MS(n)) performed using an ion trap mass spectrometer. Particular attention has been paid to isomer characterization in these precursors of azetidinones, that in turn are precursors of new beta-lactam antibiotics. 相似文献
710.
Amedeo Marini Vittorio Berbenni Giovanna Bruni Piercarlo Mustarelli Ferdinando Giordano Marco Villa 《Journal of inclusion phenomena and macrocyclic chemistry》1995,22(3):221-234
A method to determine the composition and hydration state of the complexes formed in aqueous solution by cyclodextrins (CD) is presented and applied to the -CD/ketoprofen system; it is based on a combination of spectroscopic, calorimetric, and thermogravimetric analyses. The complexes have, on average and per -CD mole, more than eleven water molecules, which are present in completely different bound states. 相似文献