RESUMEN
Silica gel was found to be an excellent medium for some useful organic transformations under organic solvent-free conditions, such as (1) the Friedel-Crafts-type nitration of arenes using commercial aqueous 69% nitric acid alone at room temperature, (2) one-pot Wittig-type olefination of aldehydes with activated organic halides in the presence of tributyl- or triphenylphosphine and Hunig's base, and (3) the Morita-Baylis-Hillman reaction of aldehydes with methyl acrylate. After the reactions, the desired products were easily obtained in good to excellent yields through simple manipulation.
Asunto(s)
Compuestos Orgánicos/química , Gel de Sílice/química , Solventes/química , Aldehídos/química , Catálisis , Ácido Nítrico/químicaRESUMEN
A novel oligosaccharide was purified from garlic (Allium sativum L.) bulbs via hot water extraction, ammonium sulfate precipitation, gel filtration and ion exchange chromatography. The molecular weight of the oligosaccharide was determined to be 1800. A nuclear magnetic resonance (NMR) study showed that ten fructose molecules were connected by beta1-2 linkage to a terminal glucose. The oligosaccharide had cytotoxic activities against human malignant lymphoma cells (U937) and colon adenocarcinoma cells (WiDr) in vitro. Furthermore, this oligosaccharide significantly suppressed the growth of murine colon adenocarcinoma cells (colon 26) in vivo. The oligosaccharide also stimulated interferon-gamma production by human peripheral blood lymphocyte in vitro, indicating that it may activate the immunological pathways and suppress the growth of tumors in vivo.
Asunto(s)
Adenocarcinoma/patología , Neoplasias del Colon/patología , Ajo/química , Interferón gamma/biosíntesis , Linfocitos/inmunología , Oligosacáridos/aislamiento & purificación , Oligosacáridos/farmacología , Células U937/efectos de los fármacos , Células U937/patología , Animales , Células Cultivadas , Relación Dosis-Respuesta a Droga , Resistencia a Antineoplásicos , Humanos , Linfocitos/metabolismo , Masculino , Ratones , Ratones Endogámicos BALB C , Peso Molecular , Oligosacáridos/química , Estimulación Química , Células Tumorales CultivadasRESUMEN
The palladium catalyzed cross-coupling reactions of aryl iodides and 5-tributylstannyl-4-fluoropyrazole prepared from fluoro(tributylstannyl)acetylene proceeded smoothly giving the corresponding 5-aryl-4-fluoropyrazole in good yields.
Asunto(s)
Paladio/química , Pirazoles/química , Acetona/análogos & derivados , Acetona/química , Catálisis , Enlace de Hidrógeno , Estructura MolecularRESUMEN
N-Methylation by sequential treatment of 5-tributylstannyl-4-fluoro-1H-pyrazole 1 with LDA and iodomethane regioselectively afforded the compound 2a in high yield. The addition reaction of 5-lithiated-4-fluoro-1H-pyrazole generated from 2a with a wide range of electrophiles allowed a facile introduction of different substituents at position 5 in good yields. The adduct 3d was efficiently converted to N-methyl-chromeno[2,3-d]pyrazol-9-one 9 in 3 steps.
Asunto(s)
Pirazoles/síntesis química , Espectroscopía de Resonancia Magnética , Pirazoles/químicaRESUMEN
A new and efficient chiral catalyst system, lanthanum-chiral BINOL-tris(4-fluorophenyl)phosphine oxide-cumene hydroperoxide, was developed for the epoxidation of alpha, beta-unsaturated ketones thus providing the corresponding epoxy ketones with excellent enantioselectivities (up to >99% ee) in good to excellent yields at room temperature.
RESUMEN
A highly efficient and practical method for obtaining alpha,beta-epoxy ketones with high optical purities was developed. The chiral lanthanum complex self-organized in situ from lanthanum triisopropoxide, (R)-BINOL, triarylphosphine oxide, and alkyl hydroperoxide (1:1:1:1) was found to catalyze the epoxidation of alpha,beta-unsaturated ketones with tert-butyl hydroperoxide or cumene hydroperoxide at room temperature to give the corresponding epoxy ketones in high enantioselectivities (up to >99% enantiomeric excess (ee)). A remarkably high asymmetric amplification, a positive nonlinear effect, was observed in the epoxidation of chalcone, which strongly suggests the formation of a dinuclear peroxide-involved mu-complex as the active catalyst.