958 resultados para Região do Alto Douro vinhateiro


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8 fotografías a color.

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39 hojas : ilustraciones, fotografías.

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92 hojas : ilustraciones, fotografías.

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La expansión de la demanda internacional de alimentos traccionada por el crecimiento de la población mundial, los nuevos hábitos de consumo y las nuevas políticas públicas de nutrición a nivel mundial, han generado un contexto positivo para el crecimiento del consumo mundial de frutas y hortalizas en general, y de la palta en particular. La palta ha sido catalogada como producto de lujo, por los beneficios que proporciona a la salud. Es así, que en respuesta a esta demanda externa, en Perú se ha venido incrementando el área cultivada con palta, experimentado un fuerte crecimiento en producción y participación en las exportaciones mundiales. El objetivo de este trabajo es conocer la situación del sector de la palta peruana. A partir de la identificación de los factores responsables de su performance actual. Se utilizó la metodología del índice de Bela Balassa e índice de Grubell y Lloyd para su análisis en el comercio internacional frente a sus principales competidores (México y Chile), y la metodología del Diamante de Porter para analizar su competitividad. La producción nacional en los últimos diez años ha logrado un aumento en más del 100 por ciento, y ha permitido ocupar actualmente el segundo lugar en las exportaciones después de México y el sexto lugar en la producción mundial. Este crecimiento esta sostenido desde el punto de vista de producir palta de la mejor calidad para el mercado externo, rendimientos por encima de los principales productores del mundo, bajos costos de producción, buenos precios de venta, entre otros. Todo esto, se ha logrado gracias a la combinación de ventajas comparativas que presenta el sector para la producción de palta y de las ventajas competitivas que se desarrollaron a través de las inversiones realizadas por el estado y las empresas privadas. La acción de estas dos ventajas, ha permitido un crecimiento sustentable, como surge del presente trabajo

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p.63-74

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Bacterial dioxygenase-catalysed cis-dihydroxylation of the tetracyclic arenes benzo[c]phenanthrene 2, and the isosteric compounds benzo[b]naphtho[1,2-d]furan 8, and benzo[b]naphtho[1,2-d]thiophene 9, has been found to occur exclusively at fjord-region bonds. The resulting cis-dihydrodiols 7, 10 and 11 were found to be enantiopure and of similar absolute configuration. cis-Dihydroxylation was also observed in the pseudo-fjord region of the 8,9,10,11-tetrahydro-precursors (12 and 13) of benzo[b]naphtho[1,2-d]furan 8, and benzo[b]naphtho[1,2-d]thiophene 9, to yield the corresponding enantiopure hexahydro cis-diols 14 and 15. A novel tandem cis-dihydroxylation and bis-desaturation of the tetrahydro-substrate, tetrahydrobenzo[b]naphtho[1,2-d]thiophene 13, catalysed by biphenyl dioxygenase, was found to yield the fjord-region cis-dihydrodiol 17 of benzo[b]naphtho[1,2-d]thiophene 9.

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Typically, Povarov reactions of imines derived from aromatic amines and aromatic aldehydes show poor exo/endo-stereoselectivity and to date no data is available on the regioselectivity of the cyclisation when 3-substituted imines are employed. We have demonstrated that reaction using acyclic enamides as the alkene component with 3-nitro substituted imines is completely regioselective and gave only the 5-nitro substituted tetrahydroquinoline. As a bonus the reaction also became completely exo-selective with the stereochemistry of the E-alkene preserved in the tetrahydroquinoline product.

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Benzene cis-diol dehydrogenase and naphthalene cis-diol dehydrogenase enzymes, expressed in Pseudomonas putida wild-type and Escherichia coli recombinant strains, were used to investigate regioselectivity and stereoselectivity during dehydrogenations of arene, cyclic alkane and cyclic alkene vicinal cis-diols. The dehydrogenase-catalysed production of enantiopure cis-diols, α-ketols and catechols, using benzene cis-diol dehydrogenase and naphthalene cis-diol dehydrogenase, involved both kinetic resolution and asymmetric synthesis methods. The chemoenzymatic production and applications of catechol bioproducts in synthesis were investigated.

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The reactions of enantiopure cyclohexene epoxides and trans-1,2-bromoacetates, derived from the corresponding substituted benzene cis-dihydrodiol metabolites, with nitrogen nucleophiles, were examined and possible mechanisms proposed. An initial objective was the synthesis of new 1,2-aminoalcohol enantiomers as potential chiral ligands and synthetic scaffolds for library generation. These apparently simple substitution reactions proved to be more complex than initially anticipated and were found to involve a combination of different reaction mechanisms. Allylic trans-1,2-azidohydrins were prepared by Lewis acid-catalysed ring-opening of cyclic vinyl epoxides with sodium azide via an S(N)2 mechanism. On heating, these trans-1,2-azidohydrins isomerized to the corresponding trans-1,4-azidohydrins via a suprafacial allyl azide [3,3]-sigmatropic rearrangement mechanism. Conversion of a 1,2-azidohydrin to a 1,2-azidoacetate moved the equilibrium position in favour of the 1,4-substitution product. Allylic trans-1,2-bromoacetates reacted with sodium azide at room temperature to give C-2 and C-4 substituted products. A clean inversion of configuration at C-2 was found, as expected, from a concerted S(N)2-pathway. However, substitution at C-4 was not stereoselective and resulted in mixtures of 1,4-cis and 1,4-trans products. This observation can be rationalized in terms of competitive S(N)2 and S(N)2 reactions allied to a [3,3]-sigmatropic rearrangement. cis-1,2-Azidohydrins and cis-1,2-azidoacetates were much more prone to rearrange than the corresponding trans-isomers. Reaction of the softer tosamide nucleophile with trans-1,2-bromoacetates resulted, predominantly, in C-4 substitution via a syn-S(N)2 mechanism. One application of the reaction of secondary amines with allylic cyclohexene epoxides, to give trans-1,2-aminoalcohols, is in the synthesis of the anticholinergic drug vesamicol, via an S(N)2 mechanism. Copyright (c) 2013 John Wiley & Sons, Ltd.

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commissioned by Ballet Rambert for 60th Anniversary season, choreographer Mary Evelyn, designer Liz Emmanuel. World premiere: Theatre Royal York 03/06/86