16 resultados para Mild Conditions

em Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho"


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Procedures for the deprotection of the 2-nitro- and 2,4-dinitrobenzenesulfonamides to give the corresponding primary amines were developed. The 2-Nitrobenzenesulfonyl group was effectively removed by HSCH2CH2OH/DBU or PhSH/Cs2CO3 in DMF under mild conditions to give the corresponding primary amines in high to excellent yield. For removal of the 2,4-dinitrobrnzenesulfonyl group, the use of thiol alone (HSCH2CH2OH or PhSH) was quite effective. Selective deprotection of 2,4-dinitrobenzene-sulfonamide in the presence of 2-nitrobznzenesulfonamide has also been achieved.

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Multicomponent reactions between phenols, β-diesters and benzaldehydes for the synthesis of 4-aryl-3,4-dihydrocoumarin derivatives were carried out under mild conditions (room temperature) and presented moderate yields (38-88%) and reasonable reaction times (2-4 days), using niobium pentachloride as a catalyst.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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One-pot multicomponent synthesis of tetrahydropyridine derivatives between aniline derivatives, benzaldehyde and two different β-keto ester (methyl and ethyl acetoacetate) using niobium pentachloride as catalyst under mild conditions, providing good yields.

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Homogeneous catalysts prepared from rhodium trichloride in aqueous aromatic amines have been shown to reduce C-CI bonds under mild water gas shift conditions (T=100 degrees C, P-CO = 1.0 atm). In a 4-picoline/water solvent mixture, 1,2-dichloroethane is reduced to ethylene and ethane in yields compatible with the consumption of the reducing agent CO and with the formation of CO2. Variation of the catalyst solutions by using different substituted pyridines shows a pattern of catalytic activity parallel to that reported previously for H-2 production from the shift reaction, There is a moderate dependence of activity on the basicity of the aromatic amine, but a methyl group at the alpha-position exercises a strong negative steric effect. Long term studies show decrease of the activity with the time perhaps due to the build up of chloride in the medium. (C) 1999 Elsevier B.V. B.V. All rights reserved.

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BACKGROUND: Vascular cells express different phenotypes in adult and fetal vessels, and the extracellular matrix they synthesize should reflect these differences. Alterations of vascular proteoglycan/glycosaminoglycan is verified in disorders such as hypertension and diabetes, and when occurring during pregnancy, they bring about structural changes to fetal vessels that often lead to impaired fetus growth. Yet there is little data about the extracellular matrix of an important human fetal vessel, the umbilical artery.EXPERIMENTAL DESIGN: This study involved the biochemical characterization of the extracellular matrix of normal umbilical arteries, umbilical arteries from complicated pregnancies (maternal hypertension and diabetes and intrauterine growth retardation syndrome), and, for purpose of comparison, normal adult arteries (aorta and iliac and pulmonary arteries). Although the collagen types I:III ratio was determined in some cases, emphasis was placed on analysis of glycosaminoglycans.RESULTS: Normal umbilical arteries differ from normal adult arteries in that they contain greater concentrations of hyaluronic acid and lesser concentrations of heparan sulfate and chondroitin 4-and 6-sulfate. The umbilical artery also differs from adult arteries in the disaccharide composition of its chondroitin and heparan sulfates and in the molecular weight of this latter glycosaminoglycan. The glycosaminoglycan distribution in umbilical arteries derived from complicated pregnancies is roughly similar to that of controls. However, total glycosaminoglycan and collagen were significantly reduced, and the collagen I:III ratio was increased in the umbilical arteries from hypertension-complicated pregnancies.CONCLUSIONS: the glycosaminoglycan composition of the normal umbilical artery, a fully differentiated tissue, differs in many aspects from that of normal adult arteries. of the cases of complicated pregnancies studied, the extracellular matrix of umbilical arteries was altered only in maternal hypertension. The changes, notably a mild fibrosis, were not very pronounced and should not impair hemodynamic properties of the vessel.