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Item The binding of 4-ethylguaiacol with polyaniline-based materials in winesAutores: Marican, A.; Carrasco-Sanchez, V.; John, A.; Laurie, VF.; Santos, LS.4-ethylguaiacol (4-EG) is one of the important compounds responsible for the "Brett character" (i.e. spicy and smoky aromas) found in wines contaminated with Brettanomyces yeast. In this trial, the ability of polyaniline-based materials (PANI-EB and PANI-ES) was tested as a potential fining agent for the removal of 4-EG in wine. First, a screening study was developed in order to determine the binding capacity of 4-EG by PANI materials in 12% ethanol solution. Then, the capturing ability of PANI against 4-EG was evaluated with a solution containing gallic acid (GA), 4-methyl-catechol (4-MC), in which the concentration of the phenolic compounds were maintained as in the real wine. The results obtained showed that the retention percentage varied between 0 to 100% (4-EG), 13.81% to 72.32% (GA), and 0 to 17.39% (4-MC), depending on the interaction time and amount of the PANI used. Finally, the capturing capacity of PANI-EB and PANI-ES against 4-EG was evaluated in a real wine sample containing originally 3.10 +/- 0.13 mg L-1 of 4-EG and 2.55 +/- 0.10 g L-1 of other total phenolic compounds. The analyses performed indicated that PANI-EB is more effective in removing 4-EG than PANI-ES, with retention percentages varying between 36 and 50%. (C) 2014 Elsevier Ltd. All rights reserved.Item Dendritic Catalysis in Asymmetric SynthesisAutores: John, A.; Nachtigall, F.M.; Santos, L.S.In this review, we have focused our attention on the application of dendrimers as asymmetric catalyst in organic synthesis, which appeared in the literature. Dendrimers have been identified as a promising candidate for catalysis application. The combination of high surface area and high solubility makes dendrimers as useful nanoscale catalysts. The main advantage of the dendritic catalysts is they can be separated from the reaction mixture by simple solvent precipitation and reused for several times with similar catalytic activity. Importance of catalytically active substances like metal salts or organic molecule like pyrrolidinylmethanol thatare attached either to the core or to the periphery of the dendrimers have been highlighted and their applications in important organic reactions such as Baylis-hillman, Mannich-type, Diels-Alder, Wittig reaction, Michael addition, addition of dialkylzinc to aldehyde, asymmetric epoxide ring opening, asymmetric hydrogenation and asymmetric epoxidation are also presented. Use of dendrimer based salts and chiral compounds in asymmetric syntheses are discussed and the advantages and disadvantages of those catalysts are brought out in this review.
