Navegando por Autor "Teixeira, Róbson R."
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Item Centrosymmetric resonance-assisted intermolecular hydrogen bonding chains in the enol form of β-diketone: Crystal structure and theoretical study(Journal of Molecular Graphics and Modelling, 2016-07) Teixeira, Róbson R.; Pereira, Wagner L.; Ellena, Javier A.; Paixão, Drielly A.; Guilardi, Silvana; Franca, Eduardo F.Isobenzofuran-1(3H)-ones (phtalides) are heterocycles that present a benzene ring fused to a γ-lactone functionality. This structural motif is found in several natural and synthetic compounds that present relevant biological activities. In the present investigation, the 3-(2-hydroxy-4,4-dimethyl-6-oxocyclohexen-1-yl)isobenzofuran-1(3H)-one was characterized by single-crystal X-ray analysis. In the crystal structure, there are two molecules per asymmetric unit. One of them exhibits resonance assisted hydrogen bonds (RAHBs). Semi-empirical and DFT calculations were performed to obtain electronic structure and π-delocalization parameters, in order to better understand the energy stabilization of RAHBs in the crystal packing of the studied molecule. The structural parameters showed good agreement between theoretical and experimental data. The theoretical investigation revealed that the RAHBs stabilization energy is directly related to the electronic delocalization of the enol form fragment. In addition, RAHBs significantly affected the HOMO and charge distribution around the conjugated system.Item Centrosymmetric resonance-assisted intermolecular hydrogen bonding chains in the enol form of -diketone: Crystal structure and theoretical study(Journal of Molecular Graphics and Modelling, 2016-06-09) Franca, Eduardo F.; Guilardi, Silvana; Paixão, Drielly A.; Teixeira, Róbson R.; Pereira, Wagner L.; Ellena, Javier A.Isobenzofuran-1(3H)-ones (phtalides) are heterocycles that present a benzene ring fused to a γ-lactone functionality. This structural motif is found in several natural and synthetic compounds that present relevant biological activities. In the present investigation, the 3-(2-hydroxy-4,4-dimethyl-6-oxocyclohexen-1-yl)isobenzofuran-1(3H)-one was characterized by single-crystal X-ray analysis. In the crystal structure, there are two molecules per asymmetric unit. One of them exhibits resonance assisted hydrogen bonds (RAHBs). Semi-empirical and DFT calculations were performed to obtain electronic structure and π-delocalization parameters, in order to better understand the energy stabilization of RAHBs in the crystal packing of the studied molecule. The structural parameters showed good agreement between theoretical and experimental data. The theoretical investigation revealed that the RAHBs stabilization energy is directly related to the electronic delocalization of the enol form fragment. In addition, RAHBs significantly affected the HOMO and charge distribution around the conjugated system.Item Cu2O spheres as an efficient source of catalytic Cu(I) species for performing azide-alkyne click reactions(Tetrahedron Letters, 2017-02-08) Rodrigues, Thenner S.; Silva, Anderson G.M. da; Oliveira, Lucas C. de; Silva, Adalberto M. da; Teixeira, Róbson R.; Camargo, Pedro H.C.We report herein the high yield synthesis of Cu2O spheres displaying well-defined shapes and monodisperse sizes that could be employed as the source of highly catalytic active Cu(I) species towards click reactions between several of alkynes and azides to produce a variety of 1,2,3-triazoles under ligand-free and ambient conditions (in an open reactor). The utilization of Cu2O spheres enabled superior performance as compared to a conventional protocol in which CuSO4 is employed in combination with sodium ascorbate as the catalyst system. In addition, the compounds were obtained in synthetically useful yields, and seven of them have not been previously reported. We believe the results reported herein shed new insights into the optimization of activity and versatility of click reactions towards the synthesis of target molecules in environmentally friendly conditions.Item Zirconium catalyzed synthesis of 2-arylidene Indan-1,3-diones and evaluation of their inhibitory activity against NS2B-NS3 WNV protease(European Journal of Medicinal Chemistry, 2018-04-10) Oliveira, Ana Flávia C. da S.; Souza, Ana Paula M. de; Oliveira, André S. de; Silva, Milene L. da; Oliveira, Fabrício M. de; Santos, Edjon G.; Silva, Ítalo Esposti P. da; Ferreira, Rafaela S.; Villela, Filipe S.; Martins, Felipe T.; Leal, Daniel H.S.; Vaz, Boniek G.; Teixeira, Róbson R.; Paula, Sergio O. deA simple and efficient Knoevenagel procedure for the synthesis of 2-arylidene indan-1,3-diones is herein reported. These compounds were prepared via ZrOCl2·8H2O catalyzed reactions of indan-1,3-dione with several aromatic aldehydes and using water as the solvent. The 2-arylidene indan-1,3-diones were obtained with 53%-95% yield within 10–45 min. The synthesized compounds were evaluated as inhibitors of the NS2B-NS3 protease of West Nile Virus (WNV). It was found that hydroxylated derivatives impaired enzyme activity with varying degrees of effectiveness. The most active hydroxylated derivatives, namely 2-(4-hydroxybenzylidene)-1H-indene-1,3(2H)-dione (14) and 2-(3,4-dihydroxybenzylidene)-1H-indene-1,3(2H)-dione (17), were characterized as noncompetitive enzymes inhibitors, with IC50 values of 11 μmol L−1 and 3 μmol L−1, respectively. Docking and electrostatic potential surfaces investigations provided insight on the possible binding mode of the most active compounds within an allosteric site.