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141.
Julia Bruno-Colmenárez Juan M. Amaro-Luis Irama Ramírez Paulino Delgado-Méndez Graciela Díaz de Delgado 《Journal of chemical crystallography》2010,40(2):110-115
Abstract
Two compounds isolated from the aerial parts of Verbesina turbacensis H.B.K, are reported in this work. Both compounds crystallize in the orthorhombic system, space group P212121. Compound (1), 6β-[cinnamoyloxy]-3β,4α-dihydroxyeudesmane, formula C24H34O4, has unit cell parameters a = 9.6234(2), b = 12.3137(3) and c = 18.6277(5) Å, V = 2207.38(9) Å3, Z = 4. On the other hand, 6β-[cinnamoyloxy]-eudesman-15-oic acid (2), formula C24H32O4, has cell parameters a = 8.7035(3), b = 14.2020(4), c = 17.1590(5) Å, V = 2120.97(11) Å3, Z = 4. 相似文献142.
Cecilia Saiz Valentina Villamil Mariano M. González Ma. Agustina Rossi Lorena Martínez Leopoldo Suescun Alejandro J. Vila Graciela Mahler 《Tetrahedron: Asymmetry》2017,28(1):110-117
The synthesis of new oxazolidinylthiazolidines bicycles, oxygen analogues of bisthiazolidines, also known as metallo-β-lactamase inhibitors is described. The reaction of β-aminoalcohols and 2,5-dihydroxy-1,4-dithiane led to oxazolidinylthiazolidines and/or dithioazabicycles as the main products. The distribution pattern depends mainly on the aminoalcohol substituents. In a one-pot reaction, four new bonds are formed in good yields and with high atom efficiency. When the oxazolidinylthiazolidines are formed, two stereogenic centres are generated with high enantiospecificity. The reaction mechanism is discussed based on crystallographic data and interconversion studies. Two oxazolidinylthiazolidines were evaluated as inhibitors of the potent lactamase NDM-1 and compound 4f displayed competitive inhibition with Ki = 1.6 ± 0.6 μM. 相似文献
143.
Graciela Boente Daniela Rodriguez Mariela Sued 《Annals of the Institute of Statistical Mathematics》2018,70(4):919-950
In many situations, when dealing with several populations, equality of the covariance operators is assumed. An important issue is to study whether this assumption holds before making other inferences. In this paper, we develop a test for comparing covariance operators of several functional data samples. The proposed test is based on the Hilbert–Schmidt norm of the difference between estimated covariance operators. In particular, when dealing with two populations, the test statistic is just the squared norm of the difference between the two covariance operators estimators. The asymptotic behaviour of the test statistic under both the null hypothesis and local alternatives is obtained. The computation of the quantiles of the null asymptotic distribution is not feasible in practice. To overcome this problem, a bootstrap procedure is considered. The performance of the test statistic for small sample sizes is illustrated through a Monte Carlo study and on a real data set. 相似文献
144.
Victor E. Marquez Benjamin B. Lim John S. Driscoll Robert Snoek Jan Balzarini Satoru Ikeda Graciela Andrei Erick De Clercq 《Journal of heterocyclic chemistry》1993,30(5):1393-1398
Synthesis of the cyclopentene carbocyclic analogue of the naturally occurring nucleoside clitocine ( 1 ) is reported. Starting with racemic cyclopentenylamine ( 10 ), the heterocyclic moieties of the clitocine analogue 4 and related 1,6-dihydro-6-oxo, 5 , and 2-amino-1,6-dihydro-6-oxo, 6 , analogues were constructed. These compounds were respectively converted to 8-aza-neplanocin A (7) , 8-aza-neplanocin D ( 8 , the inosine analogue), and the corresponding 8-aza-guanosine analogue 9 after reduction of the nitro group followed by nitrous acid cyclization. Extensive antiviral evaluation revealed that only 8-aza-neplanocin A ( 7 ) had enough antiviral activity to warrant further studies. This compound showed weak antiviral activity against HSV-1, HSV-20 and the thymidine kinase deficient (TK-) HSV-1. However, it displayed good antiviral activity against human cytomegalovirus (HCMV) at a concentration of 0.40–2.50 μg/ml, well below the cytotoxicity threshold. This activity profile is consistent with a mechanism of action involving the inhibition of the enzyme adenosylhomo-cysteine hydrolase. 相似文献
145.
Graciela Priano Graciela González Mauricio Günther Fernando Battaglini 《Electroanalysis》2008,20(1):91-97
An efficient and inexpensive eight gold electrode array has been manufactured by a combination of screen printing and gold electrodeposition techniques. Gold electrodeposition was performed in potentiostatic and galvanostatic conditions. Different treatments, involving temperature and polishing control, led to electrodes with different roughness. The electrochemical behavior of the generated gold surface was studied by cyclic voltammetry showing the characteristic response of polycrystalline gold, in contrast with disposable gold electrodes fabricated by screen printing from gold inks. The electrodes were chemically modified through the adsorption of alkanethiols self‐assembled monolayers and the coupling of a model protein. Both reactions were followed by cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS). The electrodes have shown high reproducibility in their electrochemical behavior as well as in their modifications. 相似文献
146.
Jines E. Contreras Belkis Ramírez V. Graciela Díaz de Delgado 《Journal of chemical crystallography》1997,27(7):391-395
[Cd(C5H4O4)(OH2)2] (1), crystallizes in the monoclinic system, space groupP21/n, with lattice parametersa=7.323(2),b=16.028(6),c=7.202(2) Å, β=113.11(1)°, andZ=4. The Cd atom coordinates to seven oxygens in a monocapped trigonal antiprism fashion. The antiprisms share one vertex to form chains which run approximately parallel to thec axis. The itaconate ligands link the chains to form layers which stack along theb axis. 相似文献
147.
148.
The air- and moisture-stable pentanuclear yttrium cluster H(5)[Y(5)(mu(4)-O)(mu(3)-O)(4)(mu-eta](2)-Ph(2)acac)(4)(eta](2)-Ph(2)acac)(6)](Ph(2)acac = dibenzoylmethanide) has been used as a homogeneous catalyst for the oxidation of aldehydes to the corresponding carboxylic acids in the presence of air. 相似文献
149.
150.
Robust nonparametric regression estimation 总被引:1,自引:0,他引:1
In this paper we define a robust conditional location functional without requiring any moment condition. We apply the nonparametric proposals considered by C. Stone (Ann. Statist. 5 (1977), 595–645) to this functional equation in order to obtain strongly consistent, robust nonparametric estimates of the regression function. We give some examples by using nearest neighbor weights or weights based on kernel methods under no assumptions whatsoever on the probability measure of the vector (X,Y). We also derive strong convergence rates and the asymptotic distribution of the proposed estimates. 相似文献