Browsing by Author "Zuloaga, F"

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    Synthesis of 2H-naphtho[2,3-b]thiopyranoquinones and density functional study for the Diels-Alder reaction of a benzothiopyranoquinone
    (PERGAMON-ELSEVIER SCIENCE LTD, 2000) Tapia, RA; Garate, MC; Valderrama, JA; Zuloaga, F; Jenkins, PR; Fawcett, J; Russell, DR
    The synthesis of benzothiopyranoquinone (6) in three step from benzothiopyran (3) is described. Diels-Alder reaction of quinone (6) with 1,3-pentadiene (7), cyclopentadiene, 1-methoxy-1,3-cyclohexadiene (11) and 1-dimethylamino-1-aza-1,3-pentadiene (14) was studied. The Density Functional Theory was applied to explain the orientation of the cycloaddition reaction of quinone (6) with dienes (7), (11) and (14).
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    Synthesis, crystal structure, molecular orbital calculations and electronic properties of 2,3-di(2-pyridyl)naphtho[2,3-f]quinoxaline-7,12-quinone (Aqdpp)
    (ROYAL SOC CHEMISTRY, 1998) Lopez, R; Boys, D; Loeb, B; Zuloaga, F
    The synthesis, characterization and crystal structure of 2,3-di(2-pyridyl)naphtho[2,3-f]quinoxaline-7,12-quinone (Aqdpp) are reported. Molecular orbital calculations have been carried out in order to characterize its reactivity and coordination properties. surface maps for the electronegativity, hardness and Fukui functions have been generated to identify local reactivity sites and the crystal structure has been compared with the optimized geometry with good correlation among them. The acceptor properties of the Aqdpp ligand are shown by the orbital map for the LUMO level contributed mainly by the quinonic region of the ligand.
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    Visible light induced lipoperoxidation of a parenteral nutrition fat emulsion sensitized by flavins
    (ELSEVIER SCIENCE INC, 1998) Silva, E; Gonzalez, T; Edwards, AM; Zuloaga, F
    The photosensitizing effects of riboflavin, flavin mononucleotide, flavin adenine dinucleotide,and a commercial multivitamin infusate on a lipid emulsion used in parenteral nutrient infusions were studied during exposure to polychromatic visible light. It was found that the efficiency of riboflavin (a polar flavin) as sensitizer of lipid emulsion peroxidation is greater than that of flavin mononucleotide (an ionic flavin). This was determined by measuring the consumption of molecular oxygen and the concentration of thiobarbituric acid-reactive species generated during the irradiation time. These findings are supported by molecular orbital studies of these molecules related to polarity, ionic charges around the different molecular regions, and electrostatic potentials comparisons. Flavin adenine dinucleotide (a more ionic flavin), most likely remains totally excluded from the lipid emulsion due to its polarity and molecular geometry and does not induce lipid peroxidation. The multivitamine complex seems to provide a protective effect on the lipid emulsion exposed to light, attributed to the presence of ascorbic acid, which suffers an intensive photodecomposition. A solution of vitamin C, whose concentration was equivalent to that of the parenteral mixture, consumes an considerable amount of molecular oxygen when it is irradiated with visible light in the presence of flavin mononucleotide. (C) Elsevier Science Inc. 1998.