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11.
Antonia Torres Ávila Pimenta Raimundo Braz‐Filho Piero Giuseppe Delprete Elnatan Bezerra de Souza Edilberto Rocha Silveira Mary Anne Sousa Lima 《Magnetic resonance in chemistry : MRC》2010,48(9):734-737
Two unusual monoterpene indole alkaloids, stachyoside ( 1 ) and nor‐methyl‐23‐oxo‐correantoside ( 2 ), have been isolated from the aerial parts of Psychotria stachyoides. The structural elucidation of both compounds was performed by the aid of HRESIMS, FT‐IR, and 1D‐ and 2D‐NMR techniques including COSY, HSQC, HMBC, and NOESY. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
12.
Vinicius F. Moreira Rodrigo R. Oliveira Leda Mathias Raimundo Braz‐Filho Ivo J. Curcino Vieira 《Helvetica chimica acta》2010,93(9):1751-1757
A phytochemical study on Borreria verticillata has led to the isolation of two novel simple indole alkaloids, 6‐methoxy‐4‐(3‐methylbut‐2‐en‐1‐yl)‐1H‐indole, named verticillatine A ( 1 ), and 1‐(1H‐indol‐6‐yl)‐3‐methylbutan‐1‐one, named verticillatine B ( 2 ), one new iridoid, 6′‐O‐(2‐glyceryl)scandoside methyl ester ( 3 ), with the glycerol unit linked to a glucose unit, and two known ones, asperuloside ( 4 ) and scandoside methyl ester ( 5 ). The structures of these compounds were elucidated on the basis of spectroscopic‐data analyses, mainly 1H‐ and 13C‐NMR, including 2D experiments (1H,1H‐COSY, NOESY, HMBC, and HMQC), and HR‐ESI‐MS. 相似文献
13.
G. I. Braz I. E. Kardash V. V. Kopylov A. F. Oleinik G. G. Rozantsev A. N. Pravednikov A. Ya. Yakubovich 《Chemistry of Heterocyclic Compounds》1970,4(2):251-253
The synthesis of 4,4-di(methylamino)- and 4,4-dianilino-3,3-diaminobiphenyls is described. The condensation of the tetraaminobiphenyls mentioned with phenyl perfluorobutyrate has given, respectively, 1,1-dlmethyl- and 1,1-diphenyl-2,2-(n-perfluoropropyl)-5, 5-bibenzimidazolyls. A study of the thermal stability of the 2-perfluoroalkylbenzimidazoles has shown that the replacement of the hydrogen of the imino group in these compounds by a methyl or a phenyl radical considerably increases their heat stability. 相似文献
14.
Jaécio Carlos Diniz Francisco Arnaldo Viana Odaci Fernandes Oliveira Maria Aparecida M. Maciel Maria da Conceição de Menezes Torres Raimundo Braz‐Filho Edilberto R. Silveira Otília Deusdênia L. Pessoa 《Magnetic resonance in chemistry : MRC》2009,47(2):190-193
From the roots of Cordia leucocephala (Boraginaceae), two new meroterpenoid naphthoquinones, 6‐[10‐(12,12‐dimethyl‐13α‐hydroxy‐16‐methenyl‐cyclohexyl)ethyl]‐1,4‐naphthalenedione (cordiaquinone L) and 5‐methyl‐6‐[10‐(12,12‐dimethyl‐13β‐hydroxy‐16‐methenyl‐cyclohexyl)methyl‐1,4‐naphthalenedione (cordiaquinone M) were isolated. Their structures were elucidated after detailed 1D and 2D NMR (COSY, HSQC, HMBC and NOESY) data analyses and comparison with literature data for analogous compounds. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
15.
16.
Semi‐strong and strong solutions for variable density asymmetric fluids in unbounded domains
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Pablo Braz e Silva Felipe W. Cruz Marko A. Rojas‐Medar 《Mathematical Methods in the Applied Sciences》2017,40(3):757-774
We establish the existence of local in time semi‐strong solutions and global in time strong solutions for the system of equations describing flows of viscous and incompressible asymmetric fluids with variable density in general three‐dimensional domains with boundary uniformly of class C3. Under suitable assumptions, uniqueness of local semi‐strong solutions is also proved. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
17.
We establish the existence of global in time weak solutions for the equations of asymmetric incompressible fluids with variable density, when the initial density is not necessarily strictly positive. 相似文献
18.
Virginia Freitas Rodrigues Hadria M. Carmo Rodrigo R. Oliveira Raimundo Braz Filho Leda Mathias Ivo José C. Vieira 《Chromatographia》2009,70(7-8):1191-1195
The Trichilia genus (Meliaceae) consists of about 230 species distributed throughout tropical America and its phytochemical profile is rich in terpenic metabolites. Droplet counter-current chromatography (DCCC) was used for the isolation and purification of secondary metabolites obtained from a dichloromethane fraction (2.9 g) of Trichilia quadrijuga stems. A hexane–ethyl acetate–methanol–water (1:2:1.75:1, v/v/v/v) solvent system was chosen to isolate 2β,3β,4β-trihydroxypregnan-16-one (1, 24.5 mg, 0.8%), kudtdiol (2, 45.0 mg, 1.6%) and 3-O-β-d-glucopyranosylsitosterol (3, 6.0 mg, 0.2%). The results showed that DCCC was a very effective tool for the isolation of terpenes from T. quadrijuga. 相似文献
19.
We consider spectral semi-Galerkin approximations for the strong solutions of the nonhomogeneous Navier–Stokes equations.
We derive an optimal uniform in time error bound in the H1 norm for approximations of the velocity. We also derive an error estimate for approximations of the density in some spaces
Lr.
P. Braz e Silva was supported for this work by FAPESP/Brazil, #02/13270-1 and is currently supported in part by CAPES/MECD-DGU
Brazil/Spain, #117/06. M. Rojas-Medar is partially supported by CAPES/MECD-DGU Brazil/Spain, #117/06 and project BFM2003-06446-CO-01,
Spain. 相似文献
20.
G. I. Braz G. V. Myasnikova A. Ya. Yakubovich V. P. Bazov I. E. Kardash A. N. Pravednikov 《Chemistry of Heterocyclic Compounds》1967,3(4):158-162
It is found that condensation of esters of iminocarboxylic and iminoperfluorocarboxylic acids with o-aminophenol is a convenient general method for preparing 2-alkyl, 2-perfluoroalkyl, and 2-aryl substituted benzoxazoles. Hydrochlorides of esters of iminocarboxylic acids react smoothly with o-aminophenol even at room temperature. Condensation of esters of iminoperfluorocarboxylic acids, whose hydrochlorides are unstable, is suitably carried out in the presence of an equimolecular quantity of the corresponding perfluorocarboxylic acid. 2-Alkyl(aryl) substituted benzoxazoles can also be obtained by heating o-aminophenol with esters of iminocarboxylic acids in the form of free bases. Esters of iminoperfluorocarboxylic acids also react similarly. Under similar conditions diesters of bisiminocarboxylic and bisiminoperfluorocarboxylic acids and o-aminophenol giveα, ω-di(benzoxazolyl-2) alkanes, andα, ω-di(benzoxazolyl-2) perfluoroalkanes respectively. 相似文献