Sostenibilidad de las cadenas frutícolas en El Salvador: oportunidades, retos y perspectivas.

La fruticultura no es un rubro nuevo en El Salvador, sin embargo ésta ha tomado más impulso en los últimos siete años, en gran parte por el apoyo del Programa Nacional de Frutas (MAG-FRUTALES) financiado con fondos FANTEL y ejecutado por el Instituto Interamericano de cooperación para la Agricultura (IICA). El principal motor de desarrollo de la fruticultura, por supuesto, lo representan los productores y empresarios quienes han encontrado que la fruticultura representa buenos negocios, con productos diversificados de alto valor, demandados en el mercado nacional e internacional

A more critical role for silicon in the catalytic Staudinger amidation: silanes as non-innocent reductants

Amides are ubiquitous in organic chemistry and occur in some of the most important natural and non-natural molecules such as peptides, pharmaceuticals and polymers.1 For this reason, amidation reactions are some of the most frequently carried out procedures in chemical synthesis.2 Amidation reactions between azides and carboxylic acid derivatives have found widespread application owing to the fact that they can be deployed in varied and complex reaction media.3,4,5 While many of these methods use carboxylic acid-derived activated esters, the phosphine-mediated amidation reaction between free acids and azides was reported in 1983 by Garcia and co-workers (Scheme 1A).6 The utility of the process is undermined somewhat by the production of triphenylphosphine oxide as a stoichiometric by-product. However, this problem was overcome in 2012 by Ashfeld and co-workers who reported a catalytic, traceless Staudinger ligation reaction (Scheme 1B).7 This process represents a combination of Garcia’s amidation with the work of O’Brien,8 who was the first to demonstrate chemoselective phosphine oxide reduction with phenylsilane in the context of a catalytic Wittig reaction.9–14 Given that the catalytic reaction was constructed on this basis, the authors proposed a catalytic cycle (Scheme 1C) involving two key steps: (a) phosphorus-mediated amidation via an aminophosphonium carboxylate and the reactive N,O-phosphorane; and (b) chemoselective silane-mediated phosphine oxide reduction to return the phosphine catalyst. While these two steps are established as discrete processes, their conflation into a catalytic cycle presents an intriguing chemoselectivity issue, namely the reduction of triphenylphosphine oxide in the presence of reductively labile iminophosphorane, aminophosphonium and N,O-phosphorane intermediates.1

Races among products

We will revisit a 1987 question of Rabbi Ehrenpreis. Among many things, we will provide an elementary injective proof that P_1(L,y,n)>=P_2(L,y,n) for any L,n>0 and any odd y>1 . Here, P_1(L,y,n) denotes the number of partitions of n into parts congruent to 1, y+2, or 2y mod 2(y+1) with the largest part not exceeding 2(y+1)L-2 and P_2(L,y,n) denotes the number of partitions of n into parts congruent to 2, y, or 2y+1 mod 2(y+1) with the largest part not exceeding 2(y+1)L-1.Comment: 9 pages, 1 tabl

Programmable synthesis of organic cages with reduced symmetry

Integrating symmetry-reducing methods into self-assembly methodology is desirable to efficiently realise the full potential of molecular cages as hosts and catalysts. Although techniques have been explored for metal organic (coordination) cages, rational strategies to develop low symmetry organic cages remain limited. In this article, we describe rules to program the shape and symmetry of organic cage cavities by designing edge pieces that bias the orientation of the amide linkages. We apply the rules to synthesise cages with well-defined cavities, supported by evidence from crystallography, spectroscopy and modelling. Access to low-symmetry, self-assembled organic cages such as those presented, will widen the current bottleneck preventing study of organic enzyme mimics, and provide synthetic tools for novel functional material design

Effect of diet or diet plus physical activity versus usual care on inflammatory markers in patients with newly diagnosed type 2 diabetes: The Early ACTivity in Diabetes (ACTID) randomized, controlled trial

This is the final version. Available on open access from Wiley via the DOI in this recordBACKGROUND: Inflammation plays a major role in diabetes-associated cardiovascular disease (CVD). There is uncertainty whether diet and physical activity interventions can be successfully integrated into healthcare settings and reduce markers of inflammation and risk of CVD in patients with type 2 diabetes (T2D). METHODS AND RESULTS: Systemic markers of inflammation were determined in a 12-month, real-world, multicenter, randomized, controlled trial that investigated the effect of diet, diet plus physical activity, and usual care in 593 individuals with newly diagnosed T2D. During the first 6 months, serum C-reactive protein (CRP) improved by -21 (-36 to -1.4)% and -22 (-38 to -3.1)% in diet and diet plus physical activity arms versus usual care. There were also improvements in adiponectin and soluble intercellular adhesion molecule-1 (sICAM-1). Though medication-adjusted CRP was improved between 6 and 12 months for usual care, both interventions were more successful in reducing the relative risk of a high-risk CRP level of >3 mg/L (risk ratios of 0.72 [0.55 to 0.95] for diet versus usual care and 0.67 [0.50 to 0.90] for diet plus activity versus usual care). Furthermore, sICAM-1 (a marker of vascular risk), remained substantially lower than usual care in both intervention arms at 12 months. CONCLUSIONS: Motivational, unsupervised diet and/or diet plus physical activity interventions given soon after diagnosis in real-world healthcare settings improve markers of inflammation and cardiovascular risk in patients with T2D, even after accounting for the effect of adjustments to medication to try and control blood pressure, glycated hemoglobin, and lipids. CLINICAL TRIAL REGISTRATION URL: http://www.controlled-trials.com/. Unique identifier: ISRCTN92162869.British Heart FoundationDiabetes UKUK Department of Healt

A Practical Catalytic Reductive Amination of Carboxylic Acids

We report reductive alkylation reactions of amines using carboxylic acids as nominal electrophiles. The two-step reaction exploits the dual reactivity of phenylsilane and involves a silane-mediated amidation followed by a Zn(OAc)2-catalyzed amide reduction. The reaction is applicable to a wide range of amines and carboxylic acids and has been demonstrated on a large scale (305 mmol of amine). The rate differential between the reduction of tertiary and secondary amide intermediates is exemplified in a convergent synthesis of the antiretroviral medicine maraviroc. Mechanistic studies demonstrate that a residual 0.5 equivalents of carboxylic acid from the amidation step is responsible for the generation of silane reductants with augmented reactivity, which allow secondary amides, previously unreactive in zinc/phenylsilane systems, to be reduced

Strategies for the replacement of chromic acid anodising for the structural bonding of aluminium alloys

The 40/50V Bengough-Stuart chromic acid anodise process is widely used in demanding applications as a prebond treatment. This process has a number of disadvantages and its replacement is the subject of much interest in the aerospace, automotive and defence sectors, amongst others. This paper details a number of modifications to the standard boric-sulphuric acid anodising (BSAA) process specifically to achieve satisfactory structural bond performance. These included: variations in the deoxidiser and anodising parameters, and; the use of a post anodising dip. It has been demonstrated in these studies that there are three possible methods of providing excellent durability using a variation of the standard BSAA process: the use of an electrolytic phosphoric acid deoxidiser (EPAD); a high temperature anodise at 35°C, and; the use of a post anodise phosphoric acid dip (PAD)