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991.
Armando Paneque José Fernández–Bertrán Edilso Reguera H. Yee-Madeira 《Structural chemistry》2003,14(6):551-558
The solid state reactions of hemin with KCN, Na2SxH2O, arginine, imidazole, 1-methylimidazole, 2-methylimidazole, benzimidazole, and mixtures of these basic reagents were monitored using IR, Mössbauer, and XRD techniques. All these basic substances react at the peripheral propionic acid group of hemin-forming salts. Binary mixtures of KCN, arginine, imidazole, 1-methylimidazole, 2-methylimidazole, and benzimidazole were found to form complexes with mixed ligands at the iron site of hemin. According to the structural information obtained for these mixed complexes, mechanisms for their formation are proposed. The solid state synthesis and the properties of the obtained products reveal the specifities of the involved ligands. 相似文献
992.
Ismaili L Truong TT André C Thomassin M Mozer JL Robert JF Xicluna A Refouvelet B Millet J Nicod L Guillaume YC 《Journal of AOAC International》2003,86(2):222-228
The mechanism of the binding of D,L dansyl amino acids to teicoplanin was investigated. Na+ was used as an indicator of the interactions between the solutes and teicoplanin. The number (n) of sodium ions, Na+, excluded from the solute-teicoplanin interface when analyte transfer occurred was determined. A thermodynamic study and enthalpy-entropy compensation were performed to further explore the interaction mechanism. From these results, it was shown that teicoplanin was balanced between 2 conformational states characterized by distinct enantioselective properties. This approach indicates that liquid chromatography (LC) is a useful tool to extract physicochemical and molecular information from retention data. Thus, LC can be used as a complementary technique with the conventional techniques of molecular interaction analysis. 相似文献
993.
Carreño MC Des Mazery R Urbano A Colobert F Solladié G 《The Journal of organic chemistry》2003,68(20):7779-7787
The stereocontrolled formation of cis-2,5-disubstituted tetrahydrofurans and cis-2,6-disubstituted tetrahydropyrans is achieved from enantiopure ketosulfinyl esters by reduction, Weinreb's amide, and ketone formation, followed by the reductive cyclization (Et3SiH/TMSOTf) of the resulting hydroxysulfinyl ketones. The sulfoxide-bearing heterocycles were transformed into two natural products, (-)-centrolobine (1) and both enantiomers of cis-(6-methyltetrahydropyran-2-yl)acetic acid (2). 相似文献
994.
Azomethine ylides, derived from iminoesters 1 and DBU in the presence of silver salts, react with (S)-2-p-tolylsulfinyl-2-cyclopentenone 2 in a completely regio- and endoselective manner but with a low facial selectivity, affording a mixture of two cycloadducts 3 and 4. When the ylides were prepared with LHMDS, only one diastereoisomer 3 was obtained in an almost quantitative yield. A nucleophilic addition/ring closure process easily accounts for the stereochemical results. Compounds 3 were transformed into optically pure 4-oxocyclopenta[c]dihydropyrroles and tetrahydropyrroles by elimination of the sulfinyl group. 相似文献
995.
We have studied the ring opening of nonactivated amino aziridines 1 by water under acidic conditions. Depending on the acid used, amino aziridines are cleaved at C-3 or C-2 with high regioselectivity, and total stereoselectivity, affording chiral 2,3-diaminoalkan-1-ols 3 or 1,3-diaminoalkan-2-ols 4 in high yield. 相似文献
996.
The physicochemical interactions between an active peptide sequence derived from laminin and phospholipids have been studied. The main aim is to determine the suitability of this peptide fragment to be linked to liposome's with the purpose to develop targeting devices. Results indicate that this peptide is able to insert in lipid monolayers and also to form monomolecular layers at an air/water interface. Besides, miscibility studies carried out through compression isotherms of mixed monolayers [dipalmitoyl phosphatidylcholine (DPPC)/peptide], indicate a strong interaction at 60-80% DPPC molar composition. Studies carried out with lipid bilayers indicate that the interaction is restricted to the external face of the vesicles. Moreover, the presence of this peptide in the incubation media promotes a low level of carboxyfluorescein (CF) leakage and no fusion of vesicles. These results indicate that the association of this sequence to vesicles do not produce damage of the bilayer and can be used as potential targeting vector. 相似文献
997.
Maria Giorgia Cutrufello Italo Ferino Elisabetta Rombi Vincenzo Solinas Gerardo Colón José Antonio Navío 《Reaction Kinetics and Catalysis Letters》2003,79(1):93-99
A ceria-lanthana catalytic system prepared by the sol-gel technique proved to be active in 4-methylpentan-2-ol conversion,
mainly leading to 4-methylpent-1-ene, a monomer for manufacturing polymers of high technological properties. The product distribution
strongly depends on the acid-base features of the catalyst. The catalytic behavior of the samples was examined in the light
of their acid-base properties.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
998.
999.
The diastereomers of two Ln(III)-EPTPA derivatives have been separated by reversed-phase HPLC, and the water exchange rate on their Gd(III) complexes has been directly determined by 17O NMR (H5EPTPA = ethylenepropylene-triamine-pentaacetic acid). 相似文献
1000.
Harrowven DC L'Helias N Moseley JD Blumire NJ Flanagan SR 《Chemical communications (Cambridge, England)》2003,(21):2658-2659
A new approach to eight and nine membered ring synthesis is described in which a radical ipso-substitution reaction features as a key step. 相似文献