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Hernandez-Hernandez O.,Institute Quimica Organica General CSIC | Calvillo I.,Institute Quimica Organica General CSIC | Lebron-Aguilar R.,CSIC - Institute of Physical Chemistry "Rocasolano" | Moreno F.J.,Autonomous University of Madrid | Sanz M.L.,Institute Quimica Organica General CSIC
Journal of Chromatography A | Year: 2012

Three different stationary phases (sulfoalkylbetaine zwitterionic, polyhydroxyethyl aspartamide and ethylene bridge hybrid (BEH) with trifunctionally bonded amide), operating at hydrophilic interaction liquid chromatographic (HILIC) mode, have been assayed and compared for the analysis of complex mixtures of galactooligosaccharides (GOS). Chromatographic methods have been optimized to obtain the best separation between two consecutive galactose containing standards and maltodextrins, measured on the basis of resolution. Influence of several factors such as chemical modifiers (formic acid, ammonium acetate and ammonium hydroxide), organic solvent and gradients of the mobile phases in the separation of oligosaccharides have been studied. The best results were achieved on the BEH amide stationary phase, using acetonitrile:water with 0.1% ammonium hydroxide as mobile phase, where the most of oligosaccharides were successfully resolved. Characteristic MS2 fragmentation profiles of disaccharides containing galactose, glucose and/or fructose units with different linkages were evaluated and used for the characterization of di-, tri- and tetrasaccharides of three commercial prebiotic GOS mixtures (GOS-1, GOS-2 and GOS-3) by HILIC-MSn. Similar qualitative and quantitative composition was observed for GOS-1 and GOS-3, whereas different linkages and abundances were detected for GOS-2. In general, (1→4) and (1→6) glycosidic linkages were the main structures found in GOS, although (1→2) and (1→3) linkages were also identified. Regarding molecular weight, up to pentasaccharides were detected in these samples, disaccharides being the most abundant carbohydrates. © 2011 Elsevier B.V.


Aljarilla A.,Complutense University of Madrid | Lopez J.C.,Institute Quimica Organica General CSIC | Plumet J.,Complutense University of Madrid
European Journal of Organic Chemistry | Year: 2010

Metathetical processes play a prominent role in the development of useful transformations because of their mildness, tolerance of functional groups, and synthetic potential. On the other hand, carbohydrates have gained well-deserved relevance in the study of biological processes. This review summarizes a decade of efforts in the application of cross metathesis (CM) reactions to the preparation of some relevant glycoconjugates. Cross-metathesis processes have been successfully applied to carbohydrate substrates during the last decade to give rise to a variety of glycoconjugates, including glycosylamino acids, cyclodextrin derivatives, carbohydrate-based vaccines, oligosaccharides, and glycoporphyrins © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Lopez F.,University of Santiago de Compostela | Lopez F.,Institute Quimica Organica General CSIC | Mascarenas J.L.,University of Santiago de Compostela
Chemical Society Reviews | Year: 2014

This feature review describes the development of catalytic [4+2] and [4+3] cycloadditions of allenes, as efficient and practical methodologies for assembling six and seven-membered cyclic systems. The different methodologies have been classified depending on the type of key reactive intermediate that was proposed in the catalytic cycle. This journal is © the Partner Organisations 2014.


Faustino H.,University of Santiago de Compostela | Alonso I.,University of Santiago de Compostela | Mascarenas J.L.,University of Santiago de Compostela | Lopez F.,University of Santiago de Compostela | Lopez F.,Institute Quimica Organica General CSIC
Angewandte Chemie - International Edition | Year: 2013

Gold standard: Allenamides react with aldehydes or ketones having γ, δ, or ε alkenyl groups, upon activation with suitable gold catalysts, to provide oxa-bridged systems containing seven- to nine-membered carbocycles, in a formal cascade cycloaddition. By using chiral phosphoramidite/gold or bisphosphine/gold catalysts it is possible to obtain the oxa-bridged seven- and eight-membered rings with good to high enantioselectivity. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Brokl M.,Institute Quimica Organica General CSIC | Hernandez-Hernandez O.,Institute Quimica Organica General CSIC | Soria A.C.,Institute Quimica Organica General CSIC | Sanz M.L.,Institute Quimica Organica General CSIC
Journal of Chromatography A | Year: 2011

Chromatographic methods based on different HPLC operation modes, reverse phase (RP), high performance anion exchange chromatography (HPAEC), graphitized carbon chromatography (GCC) and hydrophilic interaction liquid chromatography (HILIC), have been developed and compared for the analysis of complex mixtures of neutral oligosaccharides with functional properties. Whereas GCC gave the best chromatographic separation of isomeric oligosaccharides with the same molecular weight (R s values in the range 1.0-4.0 and 2.4-5.6 for tetra- and pentasaccharides, respectively), HILIC provided the best results for mixtures including oligosaccharides of different degrees of polymerization (R s values of maltooligosaccharides between 3.4 and 6.2). Validation of the HILIC LC-MS method proved its utility for the analysis of oligosaccharide mixtures with functional properties: relative standard deviations lower than 10%, LOD's and LOQ's in the range 12.7-130.2ngmL -1 and 39.3-402.2ngmL -1, respectively, and linearity up to 10-20μgmL -1. Quantitative data for fructooligosaccharides, gentiooligosaccharides and dextransucrase cellobiose acceptor oligosaccharides were obtained by using this method. © 2011 Elsevier B.V.


Gomez A.M.,Institute Quimica Organica General CSIC
Topics in Current Chemistry | Year: 2011

This chapter summarizes the concepts and chemistry developed by Ley's group in relation to the relevance of reactivity tuning in oligosaccharide coupling reactions. The recognition that protecting groups affect the reactivity of glycosyl donors allowed Ley's group to make imaginative use of their 1,2-diacetal protecting groups. The combination of 1,2-diacetals with the presence of different anomeric leaving groups provides up to four different levels of reactivity. The exploitation of these reactivity levels in chemoselective glycosylation processes (reactivity tuning) has allowed the development of highly simplified routes to several complex oligosaccharides in step-wise or one-pot procedures. © 2011 Springer-Verlag Berlin Heidelberg.


Alonso I.,University of Santiago de Compostela | Faustino H.,University of Santiago de Compostela | Lopez F.,Institute Quimica Organica General CSIC | Mascarenas J.L.,University of Santiago de Compostela
Angewandte Chemie - International Edition | Year: 2011

Allene-tethered dienes (1) undergo an intramolecular and highly enantioselective (4+3) cycloaddition when treated with suitable chiral phosphoramidite/gold(I) catalysts (see scheme; Ar=9-anthracenyl). The reactions provide synthetically relevant [5.3.0] and [5.4.0] fused bicyclic systems 2 with good yields, complete diastereocontrol, and excellent enantioselectivities. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Rasero-Almansa A.M.,CSIC - Institute of Materials Science | Corma A.,Polytechnic University of Valencia | Iglesias M.,CSIC - Institute of Materials Science | Sanchez F.,Institute Quimica Organica General CSIC
Green Chemistry | Year: 2014

The multifunctional heterogeneous catalyst iridium-Zr-based MOF is able to effectively catalyze the hydrogenation of aromatic compounds in high yields under mild conditions. The catalyst was found to be highly active and reusable, giving similar reactivity and selectivity after at least five catalytic uses. This journal is © the Partner Organisations 2014.


Rodriguez-Sanchez S.,Institute Quimica Organica General CSIC | Hernandez-Hernandez O.,Institute Quimica Organica General CSIC | Ruiz-Matute A.I.,Institute Quimica Organica General CSIC | Sanz M.L.,Institute Quimica Organica General CSIC
Food Chemistry | Year: 2011

Different derivatization procedures were assayed to simultaneously analyse iminosugars such as deoxynojirimycin (DNJ) or fagomine and other carbohydrates of low molecular weight by gas chromatography coupled to mass spectrometry (GC-MS) in Morus sp. Both oximation + trimethylsilylation and oximation + acetylation allowed the separation of target compounds, whereas trimethylsilyl (TMS) and acetylated derivatives showed several coelutions. Nevertheless, oximation + acetylation were discarded for giving inaccurate results for ketoses due to their incomplete derivatization. Different conditions for the conversion into trimethylsilyl oximes (TMSO) were assayed, the best results being achieved using hexamethyldisilazane with trifluoroacetic acid as silylation agent. Contents of iminosugars (DNJ, fagomine and pipecolic acid derivatives) and other carbohydrates such as mono and disaccharides, myo-inositol and galactinol isomers in mulberry extracts (fruits, leaves and branches) were determined by GC-MS using the TMSO procedure. © 2010 Elsevier Ltd. All rights reserved.


Brokl M.,Institute Quimica Organica General CSIC
Journal of agricultural and food chemistry | Year: 2010

A new method based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-ToF MS) has been developed for the first time for the analysis of complex mixtures of disaccharides previously converted to their trimethylsilyl oximes (TMSO). Among the different experimental parameters considered for optimization, both the column set combination and the dimensions of the second-dimension column were found to be the most significant with regard to the complete resolution of structurally similar disaccharides. Application of the optimized method to honey analysis allowed the separation of most of the honey disaccharides previously described in the literature. Furthermore, 12 other unknown disaccharides have been separated by this method and characterized from their mass spectral data.

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