17 results on '"José M. Otero"'
Search Results
2. Computational study of the structure of ternary ionic liquid/salt/polymer electrolytes based on protic ionic liquids
- Author
-
Alejandro Rivera-Pousa, Hadrián Montes-Campos, Diddo Diddens, José M. Otero-Mato, Luis M. Varela, Oscar Cabeza, and Andreas Heuer
- Subjects
Materials science ,Inorganic chemistry ,Salt (chemistry) ,chemistry.chemical_element ,02 engineering and technology ,Lithium acetate ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Materials Chemistry ,Ethylammonium nitrate ,Physical and Theoretical Chemistry ,Solubility ,Spectroscopy ,chemistry.chemical_classification ,Hydrogen bond ,Polymer ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,ddc:540 ,Ionic liquid ,Lithium ,0210 nano-technology - Abstract
The stability of binary mixtures of several protic ionic liquids (ethylammonium nitrate, ethylammonium acetate and ethylammonium tetrafluoroborate) with polyethylene oxide is studied by means of molecular dynamics simulations. The solubility range is seen to be wider for ethylammonium acetate, and the structure and single-particle dynamics of its ternary mixtures with lithium acetate are then studied. The structure of liquid mixtures of lithium acetate with the ionic liquid is seen to be seldom modified by the addition of the polymer, with very limited hydrogen bonding between the ionic liquid and the polymer taking place. Moreover, lithium is seen to be solvated in the liquid phase forming [Li(ACE)4]−3 tetrahedral complexes irrespective of the presence of the polymer, with very limited binding of metal cations to oxygen atoms in the polymer backbone. Hence, the registered single particle dynamics and lithium transport takes place in practically the same way as in the liquid phase with almost no interference of the polymer, contrarily to previously reported results for other ionic liquids. more...
- Published
- 2021
- Full Text
- View/download PDF
Catalog
3. Tuning the hybrid borophene−/graphene-ionic liquid interface: Effect of metal cations on the electronic and photonic properties
- Author
-
Majid Vaezzadeh, Elena López-Lago, Kazem Zhour, Hussein Fahs, Fouad El Haj Hassan, Luis M. Varela, Luis J. Gallego, and José M. Otero-Mato
- Subjects
Materials science ,Potassium ,Physics::Optics ,Ionic bonding ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,Ion ,chemistry.chemical_compound ,law ,Physics::Atomic and Molecular Clusters ,Materials Chemistry ,Borophene ,Physical and Theoretical Chemistry ,Spectroscopy ,Graphene ,Doping ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical physics ,Ionic liquid ,Density functional theory ,0210 nano-technology - Abstract
A density functional theory study of the effect of the adsorption of a mixture of potassium salt and an imidazolium-based ionic liquid on the electronic and optical properties of graphene and borophene is performed. This addition leads to a downward shift of the Dirac cone for both structures due to the electron transferred from potassium to the graphene and borophene sheets. The transferred charge to the wall and the binding energy of potassium are bigger than in the case of the adsorption of potassium on pristine graphene. The Bader analysis shows that the presence of potassium makes the charge distributions in graphene and the layers of boron atoms in borophene more homogenous and the electronic distribution in the sheets is consequently less affected by the electromagnetic interaction with the ions in the mixture. Moreover, the results show that the optical properties are altered by the metallic cation, especially at low frequencies where ionic liquid-enhanced 2D plasmons are registered due to the doping of 2D sheets by electrons transferred from the potassium atoms leading to near zero values of the parallel components of the dielectric function and refractive index. more...
- Published
- 2021
- Full Text
- View/download PDF
4. Nanoconfined ionic liquids: A computational study
- Author
-
José M. Otero-Mato, Hadrián Montes-Campos, Luis M. Varela, Luis J. Gallego, and Oscar Cabeza
- Subjects
Work (thermodynamics) ,Materials science ,Ionic bonding ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Ion ,Superposition principle ,chemistry.chemical_compound ,symbols.namesake ,Materials Chemistry ,Ethylammonium nitrate ,Physical and Theoretical Chemistry ,Spectroscopy ,Hydrogen bond ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical physics ,Ionic liquid ,symbols ,van der Waals force ,0210 nano-technology - Abstract
In this work we study how the properties of ionic liquids change upon confinement between two walls at various nanometric distances. We also find a correlation between the dynamic properties and the structure of this system under these extremely nanoconfined circumstances. We report that for ethylammonium nitrate, the ionic structure inside the simulation boxes is a consequence of a subtle combination of ion packing, hydrogen bonding, electrostatic and van der Waals forces. We also study how the dynamical properties of this material change in these conditions, showing a decrease in the ionic mobility for very low slit sizes, recovering the bulk behavior as the distance between walls increases. Moreover, when short wall separations are considered, we show that the ionic mobility at short times is a minimum when the hydrogen bonding is also a minimum. Finally, we show that the effect of the interface in the long time ion dynamics only extends to a quite small region (ca. 1.35 nm) next to the walls. We show that the overall behavior of the nanoconfined liquid in the slit pore can be described by the superposition of a bulk and a confined simulation with a fitted wall separation. To our knowledge, there are no similar studies characterizing this kind of dense ionic systems in such a fine-grain way under these ultra-nanoconfined conditions. more...
- Published
- 2020
- Full Text
- View/download PDF
5. The interaction of ammonia with the protic ionic liquid ethylammonium nitrate: A simulation study
- Author
-
Ruth M. Lynden-Bell, Anthony J. Stone, José M. Otero-Mato, Alberto Coronas, Trinidad Méndez-Morales, Luis M. Varela, and Alejandro Rivera-Pousa
- Subjects
Chemistry ,Solvation ,Ionic bonding ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Solvent ,chemistry.chemical_compound ,Ammonia ,Molecular dynamics ,Chemical physics ,Ionic liquid ,Materials Chemistry ,Molecule ,Ethylammonium nitrate ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy - Abstract
In this paper, we present a molecular dynamics study of ammonia solutions in a protic ionic liquid with a structurally similar cation, ethylammonium nitrate. Using two different models of the ammonia molecule, a conventional 4-site model and a 6-site model optimizing the dipolar and quadrupolar electron distributions, we evaluate their effect on the microstructure and single-particle dynamics of these mixtures, as well as on their behaviour at the electrochemical interface. Quite significant differences are found on the solvation of ammonia in these dense ionic solvents, the 6-atom model predicting a stronger affinity of solvent molecules for the cations of the solvent as well as a caging effect on NH3 solvation shells, not predicted by the 4-site model. Finally, we discuss the structure of the liquid layers near charged graphene walls. The structure in the layer next to the wall varies with the charge on the wall and varies with the model used for ammonia. more...
- Published
- 2020
- Full Text
- View/download PDF
6. Ionic liquids nanoconfined in zeolite-templated carbon: A computational study
- Author
-
Enrique Lomba, Hadrián Montes-Campos, Trinidad Méndez-Morales, José M. Otero-Mato, Oscar Cabeza, Luis M. Varela, Luis J. Gallego, Ministerio de Economía y Competitividad (España), Xunta de Galicia, Ministerio de Ciencia, Innovación y Universidades (España), and Centro de Supercomputación de Galicia more...
- Subjects
Materials science ,Coordination number ,Carbon nanotubes ,Ionic bonding ,chemistry.chemical_element ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,01 natural sciences ,Zeolite-templated carbon ,law.invention ,Molecular dynamics ,chemistry.chemical_compound ,law ,Materials Chemistry ,Ethylammonium nitrate ,Physical and Theoretical Chemistry ,Spectroscopy ,Hydrogen bond ,Nanoconfinement ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Ionic liquids ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical physics ,Ionic liquid ,0210 nano-technology ,Carbon - Abstract
12 pags., 17 figs., 1 tab., Molecular dynamics simulations are reported for a protic (ethylammonium nitrate) and an aprotic (1-ethyl-3-methylimidazolium tetrafluoroborate) ionic liquid nanoconfined inside a faujasite-templated carbon. The structure and dynamics of ionic species inside nanotubes of relevant sizes are studied in order to understand the behavior of the dense ionic solvents in the zeolite-templated carbon. The structure (density, coordination numbers) of the confined fluid reflects a mixed dimensionality inside the zeolite-templated carbon, while the single-particle dynamics shows fundamental changes relative to that of ionic liquids confined in carbon nanotubes. Finally, no significant differences are found between the protic and the aprotic ionic liquids, which seems to suggest that the influence of hydrogen bonding is heavily suppressed inside the zeolite-templated carbon., The financial support of the Spanish Ministry of Economy and Competitiveness (Projects MAT2017-89239-C2-1-P and MAT2017-89239-C2-2-P) is gratefully acknowledged. Moreover, this work was fundedby the Xunta de Galicia (ED431D 2017/06, ED431E 2018/08 and GRCED431C 2016/001). All these research projects were partially supportedby FEDER. H.M.-C. and J.M.O.-M. thank the Spanish Ministry of Education for their FPU grant. T. M.-M. thanks the Spanish Ministry of Science,Innovation and Universities for her Juan de la Cierva grant (IJC2018-036774-I). E.L acknowledges the support from the Agencia Estatal deInvestigación and Fondo Europeo de Desarrollo Regional (FEDER) undergrant No. FIS2017-89361-C3-2-P. Facilities provided by the Galician Supercomputing Centre (CESGA) are also acknowledged. more...
- Published
- 2020
- Full Text
- View/download PDF
7. Electronic and optical properties of borophene and graphene with an adsorbed ionic liquid: A density functional theory study
- Author
-
Elena López-Lago, Luis M. Varela, Majid Vaezzadeh, Hussein Fahs, José M. Otero-Mato, Luis J. Gallego, Kazem Zhour, and Fouad El Haj Hassan
- Subjects
Materials science ,Physics::Optics ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,Ion ,chemistry.chemical_compound ,symbols.namesake ,law ,Physics::Atomic and Molecular Clusters ,Materials Chemistry ,Borophene ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Spectroscopy ,Plasmon ,Graphene ,Fermi level ,Charge density ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical physics ,Ionic liquid ,symbols ,Density functional theory ,0210 nano-technology - Abstract
We present a comparative density functional theory study of the electronic and optical properties of graphene and borophene with an adsorbed ionic liquid. The Dirac cones of these two-dimensional nanostructures are not affected by the presence of the ionic liquid close to these sheets, not even in the borophene one in which a very small charge transfer to the ionic liquid anion is detected. However, Bader analysis and charge density calculations showed that the polarization of the ionic liquid induces a redistribution of the electric charge in both sheets as a consequence of the electromagnetic interaction between the anion and cation of the ionic liquid and the electrons on the two-dimensional materials, the effect being notably stronger in graphene than in borophene. Our calculations reveal that several changes take place in the dielectric constant and electron energy loss spectra, including shifts and damping of plasmon bands, related to electrostatically induced changes in the adsorbent surface electron charge distributions and to plasmon loss channels associated to excitations of electrons in the energy levels of the adsorbed ionic liquid species close to the Fermi level of the surface material. While only minor changes are registered in borophene plasmon spectra and in the IR and visible regions of the graphene spectra, important changes in the graphene ultraviolet C and X-ray spectra are registered due to the existence of IL electronic energy levels close to the Fermi level of graphene that are absent in borophene. more...
- Published
- 2020
- Full Text
- View/download PDF
8. Highly functionalized cyclic and bicyclic β−amino acids from sugar β−nitroesters
- Author
-
Amalia M. Estévez, George W. J. Fleet, Juan C. Estévez, José M. Otero, and Ramón J. Estévez
- Subjects
chemistry.chemical_classification ,Nitroaldol reaction ,Cyclohexane ,Bicyclic molecule ,010405 organic chemistry ,Stereochemistry ,Organic Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,Amino acid ,chemistry.chemical_compound ,chemistry ,Intramolecular force ,Drug Discovery ,Cyclopentene ,Stereoselectivity ,Cyclopentane - Abstract
The synthesis of highly functionalized bicyclic and cyclic β-amino acids from β-nitrosugars is reported. Specifically, our strategy for the synthesis of polyhydroxylated cyclopentane β-amino acids via the intramolecular C-alkylation of 6-nitro-2-O-triflates of furanosides has been applied to the preparation of the first two examples of a novel class of bicyclic β-amino acids and a novel cyclopentene β-amino acid. Also, our Henry reaction mediated strategy for the synthesis of polyhydroxylated cyclohexane β-amino acids has been extended to a divergent, stereoselective synthesis of new polysubstituted cyclohexane and cyclopentane β-amino acids. more...
- Published
- 2020
- Full Text
- View/download PDF
9. Solvation in ionic liquid-water mixtures: A computational study
- Author
-
Oscar Cabeza, Luis J. Gallego, Diddo Diddens, Volker Lesch, José M. Otero-Mato, Jens Smiatek, Luis M. Varela, and Hadrián Montes-Campos
- Subjects
Molar concentration ,Properties of water ,Chemistry ,Solvation ,Ionic bonding ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Ion ,Dipole ,chemistry.chemical_compound ,Solvation shell ,Chemical physics ,Ionic liquid ,Materials Chemistry ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy - Abstract
Solvation in mixtures of 1-ethyl-3-methylimidazolium acetate ionic liquid with water in a molar concentration of 5% is studied by means of atomistic molecular dynamics (MD) simulations. We employed a spherical coarse-grained parameterization to describe a model solute and we performed MD simulations with positively charged, negatively charged and neutral model spheres and compare the results with those previously reported in pure ionic liquids. Our study reveals that water does not significantly perturb the structure of the electric double layer neither the orientation of ions in the neighborhood of the solute particle. Although water does not seem to play any significant role in the solvation of neutral solutes, there is an excess of water in the first and second ionic solvation shell of both charged solutes, respectively. We also studied the correlation between the electric field around the negatively charged model solute and the orientation of the dipole moment of water molecules, finding that, although the dynamic properties of water molecules are almost unaltered in the presence of the solutes, and the ionic cage around the central solutes is only slightly affected upon water addition, the mobility of the spheres is drastically enhanced. more...
- Published
- 2019
- Full Text
- View/download PDF
10. Mixtures of lithium salts and ionic liquids at defected graphene walls
- Author
-
Luis M. Varela, Hadrián Montes-Campos, Luis J. Gallego, Roberto C. Longo, Oscar Cabeza, and José M. Otero-Mato
- Subjects
Materials science ,Lithium tetrafluoroborate ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,Electrochemistry ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,law ,Materials Chemistry ,Physical and Theoretical Chemistry ,Spectroscopy ,Graphene ,Charge density ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical physics ,Electrode ,Lithium ,0210 nano-technology ,Layer (electronics) - Abstract
In order to investigate the effect of defects on the structure of an electrode on the electric double layer of ionic-liquid-based electrolytes, we perform classical molecular dynamic simulations on mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and lithium tetrafluoroborate (LiBF4) near charged graphene electrodes with different percentages of single defect vacancies, assuming planarity of the defected graphene, as follows from our density-functional theory calculations. Defects on the electrode's surface modify the surface charge density at the innermost layer of the electrochemical interface, which allows studying the structure of the electric double layer at a constant density of ions without changing either the voltage or the electrolyte composition. Indeed, we report that the presence of defects on the graphene electrodes can induce structural transitions in the innermost layer of the electric double layer. This result is supported by a thorough analysis of the structural properties of the layer and its energy landscape, particularly showing that there is a direct correlation between this defect-induced layer structure and the adsorption of the salt cations at the electrode, which is of utmost importance for the usage of these novel electrolytic mixtures in actual electrochemical devices. more...
- Published
- 2019
- Full Text
- View/download PDF
11. ‘Inverted’ analogs of the antibiotic gramicidin S with an improved biological profile
- Author
-
Daan Noort, M.J. van Raaij, Annemiek D. Knijnenburg, A.J. de Neeling, Roos H. Mars-Groenendijk, Emile Spalburg, José M. Otero, Herman S. Overkleeft, Antonio L. Llamas-Saiz, P. Keizer, Varsha V. Kapoerchan, Mark Overhand, and G. A. Van Der Marel more...
- Subjects
Erythrocytes ,Stereochemistry ,medicine.drug_class ,Gram-positive bacteria ,Clinical Biochemistry ,Antibiotics ,Pharmaceutical Science ,Microbial Sensitivity Tests ,Gramicidin S ,Gram-Positive Bacteria ,Hemolysis ,Biochemistry ,Turn (biochemistry) ,chemistry.chemical_compound ,Gram-Negative Bacteria ,Drug Discovery ,medicine ,Humans ,Molecular Biology ,chemistry.chemical_classification ,biology ,Organic Chemistry ,Gramicidin ,Ornithine ,biology.organism_classification ,Cyclic peptide ,Anti-Bacterial Agents ,Amino acid ,chemistry ,Molecular Medicine ,Peptides - Abstract
A series of gramicidin S derivatives 4-15 are presented that have four ornithine residues as polar protonated side chains and two central hydrophobic amino acids with unaltered turn regions. These peptides were screened against human erthrocytes and our standard panel of Gram negative- and Gram positive bacteria, including four MRSA strains. Based on the antibacterial- and hemolytic data, peptides 13 and 14 have an improved biological profile compared to the clinically applied topical antibiotic gramicidin S. © 2012 Elsevier Ltd. All rights reserved. more...
- Published
- 2012
- Full Text
- View/download PDF
12. Studies on the Michael addition of naphthoquinones to sugar nitro olefins: first synthesis of polyhydroxylated hexahydro-11H-benzo[a]carbazole-5,6-diones and hexahydro-11bH-benzo[b]carbazole-6,11-diones
- Author
-
José C. Barcia, José M. Otero, Juan C. Estévez, Cristian O. Salas, Ramón J. Estévez, and Pablo Thomas
- Subjects
Nitroaldol reaction ,Carbazole ,Stereochemistry ,Organic Chemistry ,chemistry.chemical_element ,Biochemistry ,chemistry.chemical_compound ,chemistry ,Intramolecular force ,Drug Discovery ,Nitro ,Michael reaction ,Lithium ,Sugar - Abstract
A strategy for the synthesis of the novel (6b R ,7 R ,8 S ,9 S ,10 S ,10a R )-8-(benzyloxy)-7,9,10-trihydroxy-6b,7,8,9,10,10a-hexahydro-11 H -benzo[ a ]carbazole-5,6-dione is reported. The key steps were the Michael addition of 2-hydroxy-1,4-naphthoquinone to 1-nitrocyclohexene or 3- O -benzyl-5,6-dideoxy-1,2- O -isopropylidene-6-nitro-α- d - xylo -hex-5-enefuranose and the diastereoselective intramolecular Henry reaction of 3- O -benzyl-5,6-dideoxy-5-C-(3′-hydroxy-1′,4′-naphthoquinon-2′-yl)-1,2- O -isopropylidene-6-nitro-α- d -glucofuranose to give the key (1 S ,2 S ,3 S ,4 R ,5 R ,6 R )-3-(benzyloxy)-1,2,4-trihydroxy-5-(3′-hydroxy-1′,4′-naphthoquinon-2′-yl)-6-nitrocyclohexane. When 2-hydroxy-1,4-naphthoquinone was replaced by (1,4-dimethoxynaphthalen-2-yl)lithium, the novel (1 R ,2 S ,3 S ,4 R ,4a S ,11b S )-2-(benzyloxy)-1,3,4-trihydroxy-1,2,3,4,4a,5-hexahydro-11b H -benzo[ b ]carbazole-6,11-dione was obtained. more...
- Published
- 2012
- Full Text
- View/download PDF
13. Studies on the transformation of nitrosugars into iminosugars III: synthesis of (2R,3R,4R,5R,6R)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol and (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol
- Author
-
Amalia M. Estévez, Raquel G. Soengas, Juan C. Estévez, Ramón J. Estévez, Robert J. Nash, and José M. Otero
- Subjects
Nitroaldol reaction ,Stereochemistry ,Organic Chemistry ,Mannose ,Ring (chemistry) ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Azepane ,Nitro ,Glycoside hydrolase ,Hydroxymethyl ,Physical and Theoretical Chemistry ,Divergent synthesis - Abstract
A divergent synthesis of the two novel polyhydroxylated azepanes (2R,3R,4R,5R,6R)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol and (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol from d -mannose is described. The method involves a Henry reaction between dimethyl-tert-butylsilyl 2,3-O-isopropylidene-α- d -lyxo-pentodialdo-1,4-furanoside and 2-nitroethanol followed by a reductive ring closure of the resulting epimeric nitro aldols. Glycosidase inhibition tests showed that (2R,3R,4R,5R,6S)-2-(hydroxymethyl)azepane-3,4,5,6-tetraol exhibits a weak but selective inhibition against α- l -fucosides. more...
- Published
- 2010
- Full Text
- View/download PDF
14. Synthesis and biological evaluation of asymmetric gramicidin S analogues containing modified d-phenylalanine residues
- Author
-
Eefje Engels, Daan Noort, Gijsbert A. van der Marel, José M. Otero, Mark J. van Raaij, Henk J. Busscher, Roos H. Mars-Groenendijk, Mark Overhand, Herman S. Overkleeft, Antonio L. Llamas-Saiz, Matthijs van der Knaap, Man, Biomaterials and Microbes (MBM), and Personalized Healthcare Technology (PHT) more...
- Subjects
Erythrocytes ,Anti-microbial peptides ,Stereochemistry ,Phenylalanine ,Clinical Biochemistry ,Antimicrobial peptides ,Pharmaceutical Science ,Peptide ,Microbial Sensitivity Tests ,Gramicidin S ,Hemolysis ,Biochemistry ,Chemical synthesis ,Residue (chemistry) ,chemistry.chemical_compound ,DIFFRACTION DATA ,Gramicidin S derivatives ,Drug Discovery ,Humans ,Biological profile ,AMINO-ACIDS ,Molecular Biology ,Antibacterial agent ,chemistry.chemical_classification ,Organic Chemistry ,Gramicidin ,Biological activity ,ANTIMICROBIAL PEPTIDES ,Cyclic peptide ,Anti-Bacterial Agents ,CONFORMATION ,MODEL ,chemistry ,SOLID-PHASE ,Molecular Medicine - Abstract
The synthesis of new analogues of the cationic antimicrobial peptide gramicidin S, having a modified D-phenylalanine residue, their antibacterial properties against several Gram positive and negative strains, as well as their hemolytic activity is reported. (C) 2009 Elsevier Ltd. All rights reserved. more...
- Published
- 2009
- Full Text
- View/download PDF
15. Preliminary studies on a novel synthesis of β-amino acids: stereocontrolled transformation of d- and l-glyceraldehyde into 3-amino-2-(2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)propanoic acids
- Author
-
Juan C. Estévez, Fernando Fernández, Ramón J. Estévez, and José M. Otero
- Subjects
Tris ,chemistry.chemical_classification ,Stereochemistry ,Organic Chemistry ,Salt (chemistry) ,Catalysis ,Amino acid ,Inorganic Chemistry ,chemistry.chemical_compound ,Hydrolysis ,Propanoic acid ,chemistry ,Glyceraldehyde ,Michael reaction ,Stereoselectivity ,Physical and Theoretical Chemistry - Abstract
A stereocontrolled synthesis of the methyl ester of (2 S )-3-amino-2-((4′ S )-2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)propanoic acid from d -glyceraldehyde is described for the first time. This method involves the stereoselective Michael addition of the lithium salt of tris(phenylthio)methane to ( S )-2,2-dimethyl-4-(( E )-2-nitrovinyl)-1,3-dioxolane followed by hydrolysis of the resulting (4 S )-2,2-dimethyl-4-((2′ S )-3′-nitro-1′,1′,1′-tris(phenylthio)propan-2′-yl)-1,3-dioxolane to (2 S )-methyl 2-((4′ S )-2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)-3-nitropropanoate, which was finally reduced to the target compound. A similarly stereocontrolled transformation of l -glyceraldehyde into (2 R )-methyl 3-amino-2-((4′ R )-2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)propanoate is also described. more...
- Published
- 2006
- Full Text
- View/download PDF
16. Preliminary studies on the synthesis of rancinamycins from nitrosugars: first total synthesis of (3S,4S,5S,6R)-5-benzyloxy-6-hydroxy-3,4-(isopropylidendioxy)-cyclohex-1-enecarbaldehyde
- Author
-
Fernando Fernández, José M. Otero, Ramón J. Estévez, and Juan C. Estévez
- Subjects
Inorganic Chemistry ,Chemistry ,Stereochemistry ,Organic Chemistry ,Michael reaction ,Enantioselective synthesis ,Total synthesis ,Stereoselectivity ,Physical and Theoretical Chemistry ,Catalysis - Abstract
The first total synthesis of (3S,4S,5S,6R)-5-benzyloxy-6-hydroxy-3,4-(isopropylidendioxy)-cyclohex-1-enecarbaldehyde from d -glucose is described. The key steps of this synthesis are the stereoselective Michael addition of 2-lithio-1,3-dithiane to 3-O-benzyl-5,6-dideoxy-1,2-O-isopropylidene-6-nitro-α- d -xilo-hex-5-enofuranose followed by the enantioselective two-step transformation of 3-O-benzyl-5,6-dideoxy-5-C-(1,3-dithian-2-yl)-6-nitro-β- l -idofuranose into (1S,2S,3S,4S,5S,6R)-5-benzyloxy-6-hydroxy-3,4-(isopropylidendioxy)-2-nitro-cyclohexanecarbaldehyde propylene dithioacetal, which was finally converted into the target compound. more...
- Published
- 2005
- Full Text
- View/download PDF
17. Preliminary studies on the incorporation of sugars into naphthoquinones: synthesis of (1R,2S,3S,4R,4aS,11bS)-2-(benzyloxy)-1,2,3,4,4a,5-hexahydro-1,3,4-trihydroxy-11bH-benzo[b]carbazole-6,11-dione
- Author
-
Ramón J. Estévez, Juan C. Estévez, José C. Barcia, and José M. Otero
- Subjects
Nitroaldol reaction ,Carbazole ,Stereochemistry ,Organic Chemistry ,Enantioselective synthesis ,Total synthesis ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Intramolecular force ,Michael reaction ,Stereoselectivity ,Physical and Theoretical Chemistry - Abstract
The first total synthesis of (1 R ,2 S ,3 S ,4 R ,4a S ,11b S )-2-(benzyloxy)-1,2,3,4,4a,5-hexahydro-1,3,4-trihydroxy-11b H -benzo[ b ]carbazole-6,11-dione from D -glucose is described. The key steps of this synthesis are the stereoselective Michael addition of 2-lithium-1,4-dimethoxynaphthalene to 3- O -benzyl-5,6-dideoxy-1,2- O -isopropylidene-6-nitro-α- D - xilo hex-5-enefuranose followed by the enantioselective intramolecular Henry reaction of 3- O -benzyl-5,6-dideoxy-5- C -(1,4-dimethoxynaphthalene-2-yl)-6-nitro-β- l -idofuranose to the key (1 R ,2 S ,3 S ,4 R ,5 S ,6 S )-3-(benzyloxy)-5-(1,4-dimethoxynaphthalene-2-yl)-1,2,4-trihydroxy-6-nitrocyclohexane. more...
- Published
- 2005
- Full Text
- View/download PDF
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.