Gold-catalyzed direct cycloketalization of acetonide-tethered alkynes in the presence of water

A methodology for the direct preparation of bridged acetals from acetonide-tethered alkynes under gold catalysis in the presence of water has been developed. The bicyclic ring structures bearing a bridged five-membered ring arise from the regioselective bis-oxycyclization by initial attack of the oxygen atom to the internal alkyne carbon. © 2012 Elsevier Ltd. All rights reserved.Peer Reviewe

Novel achievements with an old metal: Copper-promoted synthesis of four-membered azacycles

The synthesis of four-membered azacycles is of importance because of the chemical and biological relevance of these compounds. Recent progress in copper-catalyzed reactions has been applicable to a variety of research fields, such as heterocyclic synthesis. The aim of the current review is to summarize the synthesis of strained four-membered ring taking advantage of copper catalyzed and mediated processes. © 2014 The Royal Society of Chemistry.Peer Reviewe

Stereoselective cyanation of 4-formyl and 4-imino-β-lactams: Application to the synthesis of polyfunctionalized γ-lactams

The stereoselective reaction of 4-oxoazetidine-2-carbaldehydes and their corresponding imines with cyanide-based reagents give β-lactam α-aminonitriles, which are chameleonic building blocks for the controlled synthesis of a variety of new compounds including functionalized γ-lactams, succinimide derivatives, and diamino-lactams derivatives in optically pure form. © 2012 Elsevier Ltd. All rights reserved.Peer Reviewe

Iodine recycling via 1,3-migration in iodoindoles under metal catalysis

3-Substituted (indol-2-yl)-α-allenols show divergent patterns of reactivity under metal catalysis. An unprecedented intramolecular 1,3-iodine migration is described. © 2013 The Royal Society of Chemistry.Peer Reviewe

Síntesis, resolución y estudio de propiedades quirópticas de cetonas policíclicas

El presente trabajo forma parte de un plan de investigación programado en colaboración con los profesores W. Klyne y D. N. Kirk, del Departament of Chemistry del Westfield College de Londres, los cuales vienen realizando desde hace algunos años un amplio estudio sobre el dicroismo circular de cetonas policíclicas quirales, de estructura relacionada con la de oxo-compuestos esteroídicos, en la región espectral correspondiente a longitudes de onda de 350-185 nm, que permita el establecimiento de correlaciones estructurales entre el signo y magnitud de los efectos Cotton debidos a las transiciones n© p* y n© s* que presentan estos compuestos y su estereoquímica. En este tipo de investigación es necesario el estudio de moléculas modelo de estructura simplificada que permitan con mayor facilidad de inducción de reglas empíricas. Con este propósito hemos llevado a cabo la obtención de algunas cetonas policíclicas recémicas, dentro de la serie de decalona extendida todo-trans, que posteriormente fueron objeto de resolución óptica y finalmente estudiadas por dicroismo circular. Se han sintetizado por primera vez las siguientes cetonas racémicas:1. (±)-trans-sin-trans-sin-trans-2-perhidronaftacenona. 2. (±)-trans-sin-trans-1-perhidroantracenona.3.(±)-trans-anti-trans-2-perhidrofenantrenona. Su obtención ha sido fruto de un planteamiento sintético general al cual se llega mediante la consideración cuidadosa de sus estructuras y de un examen crítico de las distintas alternativas de síntesis de las mismas, y que se basa en el empleo sistemático, aunque no exclusivo, de dos tipos básicos de reacciones: la secuencia de anelación de Robinson y la reducción de agrupamientos enónicos con Liu/NH3. Se describen y se discuten igualmente una larga lista de productos intermedios y subproductos de síntesis involucrados en la preparación de tales sustratos cetónicos. La resolución óptica de las cetonas perhidronadtacénica y perhidroantracénica, efectuada por vía indirecta a través de sus OH-eq alcoholes, por recristalización fraccionada de la mezcla de ésteres diastereómeros obtenidos con el ácido 3ß-acetoxi-?5-etiénico nos ha permitido preparar muestras ópticamente puras de tales cetonas policíclicas y de algunos de sus derivados (alcoholes y acetatos). Se analizan los espectros de dicroismo circular obtenidos para las diferentes formas enantiómeras puras en disolventes de distinta polaridad, y se comparan con los de sustancias naturales de estructuras referibles (en especial de tipo esteroídico). A partir de estos datos se deduce la contribución al valor de ?e de los nuevos elementos estructurales introducidos en los esqueletos base. Las principales conclusiones que se deducen de nuestro estudio pueden resumirse en los siguientes puntos: 1. Comparando los valores de ?e observados para la cetona tetracíclica con los de su ciclohomóloga tricíclica referible se observa un incremento en el valor absoluto de ?e de 0. 2 unidades, debido a que el zig-zag primario se incrementa en dos nuevos enlaces C-C con la introducción de un anillo extra. 2. Los valores de ?e observados para la cetona tricíclica no difieren significativamente de los de la trans-1-decalona, debido a que el nuevo anillo no altera el sistema de enlace en zig-zag primario

Use of Schizosaccharomyces strains for wine fermentation? Effect on the wine composition and food safety

Schizosaccharomyceswas initially considered as a spoilage yeast because of the production of undesirable metabolites such as acetic acid, hydrogen sulfide, or acetaldehyde, but it currently seems to be of great value in enology.o ced Nevertheless, Schizosaccharomyces can reduce all of the malic acid in must, leading to malolactic fermentation. Malolactic fermentation is a highly complicated process in enology and leads to a higher concentration of biogenic amines, so the use of Schizosaccharomyces pombe can be an excellent tool for assuring wine safety. Schizosaccharomyces also has much more potential than only reducing the malic acid content, such as increasing the level of pyruvic acid and thus the vinylphenolic pyranoanthocyanin content. Until now, few commercial strains have been available and little research on the selection of appropriate yeast strains with such potential has been conducted. In this study, selected and wild Sc. pombe strains were used along with a Saccharomyces cerevisiae strain to ferment red grape must. The results showed significant differences in several parameters including non-volatile and volatile compounds, anthocyanins, biogenic amines and sensory parameters

Selected Schizosaccharomyces pombe Strains Have Characteristics That Are Beneficial for Winemaking

At present, wine is generally produced using Saccharomyces yeast followed by Oenococus bacteria to complete malolactic fermentation. This method has some unsolved problems, such as the management of highly acidic musts and the production of potentially toxic products including biogenic amines and ethyl carbamate. Here we explore the potential of the fission yeast Schizosaccharomyces pombe to solve these problems. We characterise an extensive worldwide collection of S. pombe strains according to classic biochemical parameters of oenological interest. We identify three genetically different S. pombe strains that appear suitable for winemaking. These strains compare favourably to standard Saccharomyces cerevisiae winemaking strains, in that they perform effective malic acid deacidification and significantly reduce levels of biogenic amines and ethyl carbamate precursors without the need for any secondary bacterial malolactic fermentation. These findings indicate that the use of certain S. pombe strains could be advantageous for winemaking in regions where malic acid is problematic, and these strains also show superior performance with respect to food safety

The Rise and Fall of a Change from Below in early modern Spanish: the Periphrasis Deber De + Infinitive in Texts of Linguistic Immediacy

This paper deals with the patterns of variation and change undergone by a syntactic variable in early modern Spanish grammar, namely the alternation between deber ‘have to, must/should’ and deber de + infinitive ‘have to, must/should’ as a modal periphrasis. Based on a 1,500,000 word corpus of immediacy text (private letters, memories) the results of this variationist study suggest that, throughout the 16th century, but more especially during its second half, the prepositional periphrasis gradually became more common, above all in stylistic contexts predominated by the spontaneity and proximity of the relationships between the interlocutors. It was also more frequently found in contexts involving members of northern speech communities, particularly males, the young, and the middle-low social strata, the incidence being especially high at the points where some of these groups intersect. All this suggests a change from below in the Golden Age period, which reached considerable dimensions in a relatively short time, but was destined to stagnate and later decline just as quickly in the centuries that followed as a result of some structural features, such as the special ‘visibility’ of the preposition, which could have led to the stigmatization of the periphrasis in a similar way to what happened in other Spanish syntactic phenomena