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11.
Garcia Ruano JL Alcudia A del Prado M Barros D Maestro MC Fernandez I 《The Journal of organic chemistry》2000,65(10):2856-2862
The addition of the lithium anions derived from (R)- and (S)-methyl and -ethyl p-tolyl sulfoxides to (S)-N-benzylidene-p-toluenesulfinamide provides an easy access route to enantiomerically pure beta-(N-sulfinyl)amino sulfoxides. Stereoselectivity can be achieved when the configurations at the sulfur atoms of the two reagents are opposite (matched pair), thus resulting in only one diastereoisomer, even for the case in which two new chiral centers are created. The N-sulfinyl group primarily controls the configuration of the carbon bonded to the nitrogen, whereas the configuration of the alpha-sulfinyl carbanion seems to be responsible for the level of asymmetric induction, as well as for the configuration of the new stereogenic C-SO carbon in the reactions with ethyl p-tolyl sulfoxides. An efficient method for transforming the obtained beta-(N-sulfinyl)amino sulfoxides into optically pure beta-amino alcohols, based on the stereoselective non-oxidative Pummerer reaction, is also reported. 相似文献
12.
The variation of the logrithms of stability constants of iron(III) monochelated compounds with structurally similar 1,3-dicarbonylic compounds has been found to be an essentially linear function of the negative logarithms of the acid ionization constant of the ligands. An analytical correlation which could be useful to predict equilibrium constants of iron(III) chelates has been developed. From spectrophotometric and potentiometric data a quantitative evaluation of the stability of the complex has been carried out. Results have provided information regarding substituent effects on the equilibrium constants. 相似文献
13.
14.
J. Montero 《The Journal of the Operational Research Society》1993,44(10):1025-1034
This paper deals with general structure functions, where arbitrary degrees of performance between perfect functioning and complete failure are allowed for each component and the n-component system itself. We make the assumption that the n-component system can be modelled as a structure function given by a mapping φ:L n →L k 0, L and L0 being two linearly ordered sets, so that the performance of the system is evaluated according to k single criteria. Global concepts of minimal path and minimal cut are discussed for these multicriteria systems; general reliability bounds based on them are deduced and compared with those given in previous papers. 相似文献
15.
Ana Montero 《Tetrahedron letters》2005,46(3):401-405
A stereocontrolled synthesis of an unsaturated sugar bearing two amino groups (one of them masked as an azide), using an Overman rearrangement as key step, is described. This scaffold is used to prepare two peptides having aromatic fragments, which have shown activity as calpain inhibitors. 相似文献
16.
A. Montero Alvarez J. R. Estévez Alvarez R. Padilla Alvarez 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(2):427-433
The aim of this work consisted on the implementation of sufficiently accurate and sensitive analytical procedure for the analysis
of metal concentration in rainwater. Different sample preparation procedures were tested to achieve the required concentration
prior to direct total reflection X-ray fluorescence (TXRF) analysis. TXRF and anodic stripping voltammetry (ASV) were compared
in regard to achieved detection limits, precision and accuracy. 相似文献
17.
Jiménez-Hernández ME Orellana G Montero F Portolés MT 《Photochemistry and photobiology》2000,72(1):28-34
The capability of the new luminescent probe (dibenzo[h,j] dipyrido[3,2-a:2',3'-c]phenazine)bis(2,2'-bipyridine)ruthenium(II) dication, (RB2Z), to discriminate live and dead cells has been tested on rat hepatocytes and mouse lymphocytes. RB2Z-stained cells were analyzed using flow cytometry, fluorescence (confocal) microscopy and time-resolved luminescence measurements. The established viability probes propidium iodide (PI) and SYTOX green (SG) were used as controls. The intense luminescence of RB2Z at 606 nm is localized in the nucleus of nonviable cells. Viability measurements by flow cytometry and fluorescence microscopy using RB2Z as dead-cell marker yield the same results as PI and SG. The luminescence lifetime of RB2Z also displays sensitivity to cell viability (0.45 and 0.82 microsecond in presence of fully viable and dead cells, respectively). This ruthenium complex is photostable under laser sources and its 200 nm Stokes shift facilitates multicolor labeling experiments in flow cytometry and fluorescence microscopy. Unlike the currently available probes, the long-lived excited state of RB2Z also allows assays based on luminescence decay measurements. 相似文献
18.
Garcia Ruano JL Alemparte C Martin Castro AM Adams H Rodriguez Ramos JH 《The Journal of organic chemistry》2000,65(23):7938-7943
The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles. 相似文献
19.
L. Barral F.J. Díez S. García-Garabal J. López B. Montero R. Montes C. Ramírez M. Rico 《European Polymer Journal》2005,41(7):1662-1666
Lifetime of the epoxy system formed by diglycidyl ether of bisphenol A, DGEBA/4,4′-diaminediphenylmethane, DDM, modified with the silsesquioxane, glycidylisobutyl-POSS, was calculated from thermogravimetric analysis. The activation energy of the decomposition of this system was evaluated by the integral method developed by Flynn-Wall-Ozawa (E = 88.9 ± 2.1 kJ mol−1) and by Coats and Redfern method (E = 85.2 ± 1.5 kJ mol−1). The kinetic parameters have been used to estimate the lifetime of the system POSS/DGEBA/DDM. The obtained results by two different ways are similar. 相似文献
20.
Mathematische Zeitschrift - In this article, we study Newton–Okounkov bodies on projective vector bundles over curves. Inspired by Wolfe’s estimates used to compute the volume function... 相似文献