Samarium Diiodide Mediated Reductive Coupling of Epoxides and Carbonyl Compounds: A New Stereocontrolled Synthesis of C-Glycosides from 1,2-Anhydro Sugars

The significant advances in the understanding of the biological function of carbohydrates and glycoconjugates achieved during the last two decades have stimulated the development of glycomimetics as fundamental tools for biological research and as potential agents for therapeutic intervention. C-Glycosides are of special relevance in this context due to their resistance to hydrolysis and to their occurrence in a number of natural products with interesting biological activity. Methods for their preparation using anomeric anions, cations, radicals, and carbenes have been extensively studied. 1,2-Anhydro sugars, readily available and well-known donors for the stereoselective preparation of O-glycosides, have also found application in the stereoselective synthesis of C-glycosides.This work was supported by the Ministry of Science and Technology of Spain (project BQU2000-1501-C02-01).Peer reviewe

Ketone-Imide versus Ketone-Oxime Reductive Cross-Coupling Promoted by Samarium Diiodide: New Mechanistic Insight Gained from a Failed Aminocyclopentitol Synthesis

10 páginas, 5 figuiras, 5 esquemas, 2 tablas.-- Supporting Information Available: General experimental procedures, 1D (1H and 13C) and 2D NMR (DQ-COSY, NOESY, HSQC, and HMBC) spectra for compounds 11-15, and energies and Cartesian coordinates for compounds in Table 2. This material is available free of charge via the Internet at http://pubs.acs.org.The intramolecular 1,6-ketone/imide reductive coupling promoted by samarium diiodide competes favorably with an alternative 1,5-ketone/oxime ether coupling in a keto-oxime substrate derived from d-glucosamine N-protected with a phthalimido group. This pinacol coupling reaction affords new homochiral α-hydroxylactam scaffolds that could be useful in diversity-oriented synthesis. A mechanistic proposal for this reaction that explains the experimental results is supported by DFT quantum-mechanical calculations on model compounds.Financial support by the Ministry of Science and Technology of Spain (project BQU2000-1501-C02-01) is gratefully acknowledged.Peer reviewe

Event-related brain potentials in the study of inhibition: cognitive control, source localization and age-related modulations

In the previous 15 years, a variety of experimental paradigms and methods have been employed to study inhibition. In the current review, we analyze studies that have used the high temporal resolution of the event-related potential (ERP) technique to identify the temporal course of inhibition to understand the various processes that contribute to inhibition. ERP studies with a focus on normal aging are specifically analyzed because they contribute to a deeper understanding of inhibition. Three time windows are proposed to organize the ERP data collected using inhibition paradigms: the 200 ms period following stimulus onset; the period between 200 and 400 ms after stimulus onset; and the period between 400 and 800 ms after stimulus onset. In the first 200 ms, ERP inhibition research has primarily focused on N1 and P1 as the ERP components associated with inhibition. The inhibitory processing in the second time window has been associated with the N2 and P3 ERP components. Finally, in the third time window, inhibition has primarily been associated with the N400 and N450 ERP components. Source localization studies are analyzed to examine the association between the inhibition processes that are indexed by the ERP components and their functional brain areas. Inhibition can be organized in a complex functional structure that is not constrained to a specific time point but, rather, extends its activity through different time windows. This review characterizes inhibition as a set of processes rather than a unitary process

Duality and polyhedrality of cones for Mori dream spaces

Our goal is twofold. On one hand we show that the cones of divisors ample in codimension $k$ on a Mori dream space are rational polyhedral. On the other hand we study the duality between such cones and the cones of $k$-moving curves by means of the Mori chamber decomposition of the former. We give a new proof of the weak duality property (already proved by Payne and Choi) and we exhibit an interesting family of examples for which strong duality holds.Comment: 20 pages, 1 figur

Single and joint effects of cadmium and selenium on bioaccumulation, oxidative stress and metabolomic responses in the clam Scrobicularia plana

Selenium (Se) is a vital trace element for many living organisms inclusive of aquatic species. Although the antagonistic action of this element against other pollutants has been previously described for mammals and birds, limited information on the join effects in bivalves is available. To this end, bivalves of the species Scrobicularia plana were exposed to Se and Cd individually and jointly. Digestive glands were analysed to determine dose-dependent effects, the potential influence of Se on Cd bioaccumulationas well as the possible recover of the oxidative stress and metabolic alterations induced by Cd. Selenium co-exposure decreased the accumulation of Cd at low concentrations. Cd exposure significantly altered the metabolome of clams such as aminoacyltRNA biosynthesis, glycerophospholipid and amino acid metabolism, while Se co-exposure ameliorated several altered metabolites such asLysoPC (14:0), LysoPE (20:4), LysoPE (22:6), PE (14:0/18:0), PE (20:3/18:4) andpropionyl-Lcarnitine. Additionally, Se seems to be able to regulate the redox status of the digestive gland of clams preventing the induction of oxidativedamage in this organ. This study shows the potential Se antagonism against Cd toxicity in S. plana and the importance to study join effects of pollutants to understand the mechanism underlined the effects.This study has been carried out within the research projects (CTM2012-38720-C03-03 and CTM2016-75908-R) founded by the Spanish Ministry of Economy and Competitiveness, who also provided a pre-doc grant for Chiara Trombini (BES-2013-063426), and the project PGC-2018- 096608-B-C21 from the Spanish Ministry of Science and innovation (MCIN). (Generaci´on del Conocimiento. MCIN/AEI/ 10.13039/501100011033/FEDER “Una manera de hacer Europa”). Authors are grateful to FEDER (European Community) for financial support, Grant UNHU13-1E-1611. Rodríguez-Moro, G. thanks to Plan Andaluz de Investigaci´on, Desarrollo e Innovaci´on (PAIDI 2020) and European Union for a post-doctoral grant (DOC_01115). Funding for open access charge: Universidad de Huelva / CBUA

Nonafluorobutanesulfonyl Azide: A Shelf-Stable Diazo Transfer Reagent for the Synthesis of Azides from Primary Amines

6 páginas, 2 esquemas, 2 tablasNonafluorobutanesulfonyl azide is an efficient, shelf-stable and cost-effective diazo transfer reagent for the synthesis of azides from primary amines. The reagent can also be successfully applied to the one-pot regioselective synthesis of 1,2,3-triazoles from primary amines by a sequential diazo transfer and azide–alkyne 1,3-dipolar cycloaddition process catalyzed by copper. The cycloaddition step can be conducted in an inter- or intramolecular way to afford 1,4- or 1,5-disubstituted triazoles, respectively. The atypical 1,5-regioselectivity under copper catalysis is a consequence of geometrical constraints of the amino-alkyne substrates used in the intramolecular version. Nonafluorobutanesulfonyl azide offers an advantageous alternative to the better known and most commonly used trifluoromethanesulfonyl azide.We thank the Spanish Ministerio de Ciencia e Innovación (projects CTQ-2006-15515-C02-02/BQU and CTQ2009- 14551-C02-02) and Comunidad de Madrid (project S2009/ PPQ-1634 “AVANCAT”) for financial support. We also thank Ministerio de Ciencia e Innovación for a FPU predoctoral fellowship to B. T. and C.S.I.C. for a JAE-Doc contract to J. R. S., a JAE-Predoc fellowship to M. E. P.-O., and a JAE-Intro fellowship to R. M.-B.Peer reviewe

Efficient multi-click approach to well-defined two-faced octasilsesquioxanes: the first perfect Janus nanocube

The preparation of the first structurally well-defined Janus nanocube showing two chemically distinct opposed faces is described. The synthetic approach is based on a highly efficient and symmetrycontrolled CuAAC functionalization of an octa-azido cubic silsesquioxane with a conformationally constrained tetra-alkyne with an appropriate spatial orientation of the triple bonds.with two sets of orthogonally reactive functional groups. We gratefully acknowledge financial support by the Spanish Ministerio de Ciencia e Innovación (project MAT2010-20646- C04-03) and Ministerio de Economía y Competitividad (project MAT2014-51937-C3-1-P). We also acknowledge the Spanish Ministerio de Economía y Competitividad for a FPI contract to A. B., and CSIC for a JAEDOC contract to J. R. S. and a JAEPRE contract to M. E. P.-O., and for support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe

An Effective Method for InSAR Mapping of Tropical Forest Degradation in Hilly Areas

Current satellite remote sensing methods struggle to detect and map forest degradation, which is a critical issue as it is likely a major and growing source of carbon emissions and biodiveristy loss. TanDEM-X InSAR phase height is a promising variable for measuring forest disturbances, as it is closely related to the mean canopy height, and thus should decrease if canopy trees are removed. However, previous research has focused on relatively flat terrains, despite the fact that much of the world's remaining tropical forests are found in hilly areas, and this inevitably introduces artifacts in sideways imaging systems. In this paper, we find a relationship between InSAR phase height and aboveground biomass change in four selectively logged plots in a hilly region of central Gabon. We show that minimising multilooking prior to the calculation of InSAR phase height on a pixel-by-pixel basis. This shows that TanDEM-X InSAR can measure the magnitude of degradation, and that topographic effects can be mitigated if data from multiple SAR viewing geometries are available

The Grape Gene Reference Catalogue as a Standard Resource for Gene Selection and Genetic Improvement

Effective crop improvement, whether through selective breeding or biotech strategies, is largely dependent on the cumulative knowledge of a species' pangenome and its containing genes. Acquiring this knowledge is specially challenging in grapevine, one of the oldest fruit crops grown worldwide, which is known to have more than 30,000 genes. Well-established research communities studying model organisms have created and maintained, through public and private funds, a diverse range of online tools and databases serving as repositories of genomes and gene function data. The lack of such resources for the non-model, but economically important, Vitis vinifera species has driven the need for a standardised collection of genes within the grapevine community. In an effort led by the Integrape COST Action CA17111, we have recently developed the first grape gene reference catalogue, where genes are ascribed to functional data, including their accession identifiers from different genome-annotation versions (https://integrape.eu/resources/genes-genomes/). We present and discuss this gene repository together with a validation-level scheme based on varied supporting evidence found in current literature. The catalogue structure and online submission form provided permits community curation. Finally, we present the Gene Cards tool, developed within the Vitis Visualization (VitViz) platform, to visualize the data collected in the catalogue and link gene function with tissue-specific expression derived from public transcriptomic data. This perspective article aims to present these resources to the community as well as highlight their potential use, in particular for plant-breeding applications