Chiral gold(I) vs chiral silver complexes as catalysts for the enantioselective synthesis of the second generation GSK-hepatitis C virus inhibitor

The synthesis of a GSK 2nd generation inhibitor of the hepatitis C virus, by enantioselective 1,3-dipolar cycloaddition between a leucine derived iminoester and tert-butyl acrylate, was studied. The comparison between silver(I) and gold(I) catalysts in this reaction was established by working with chiral phosphoramidites or with chiral BINAP. The best reaction conditions were used for the total synthesis of the hepatitis C virus inhibitor by a four step procedure affording this product in 99% ee and in 63% overall yield. The origin of the enantioselectivity of the chiral gold(I) catalyst was justified according to DFT calculations, the stabilizing coulombic interaction between the nitrogen atom of the thiazole moiety and one of the gold atoms being crucial.

Binap-gold (I) versus Binap-silver trifluoroacetate complexes as catalysts in 1,3-dipolar cycloadditions of axomethine ylides

The 1,3-dipolar cycloaddition between azomethine ylides and alkenes is efficiently catalysed by [{(Sa)-Binap-Au(tfa)}2] (Binap=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl; tfa=trifluoroacetyl). Maleimides, 1,2-bis(phenylsulfonyl)ethylene, chalcone and nitrostyrene were suitable dipolarophiles even when using sterically hindered 1,3-dipole precursors. The results obtained in these transformations improve the analogous ones obtained in the same reactions catalysed by [Binap–Ag(tfa)]. In addition, computational studies have also been carried out to demonstrate both the high enantioselectivity exhibited by the chiral gold(I) complex, and the non-linear effect observed in this transformation.

15 anys de còmic-vinyetes a la Universitat d’Alacant: Unicòmic com a model acadèmic de didàctica i promoció de la lectura

El 2013 s’organitzaran les XV Jornades del Còmic de la Universitat d’Alacant-Unicòmic, celebrades ininterrompudament des del 1999. D’una petita proposta de l’alumnat, hem passat a unes jornades acadèmiques estables i reconegudes, centrades en les possibilitats didàctiques del nové art. Al llarg de les quinze edicions, hi han desfilat autors de renom internacional com Chris Claremont, Francisco Solano López o Carlos Giménez, a banda de nombrosos especialistes que ens van presentar els seus treballs al voltant del món de la historieta, com Álvaro Pons o Antonio Martín. En el següent estudi, s’hi fa un minuciós recorregut per l’organització i la història de les jornades tot destacant els moments més rellevants i la importància que han tingut aquestes jornades per al reconeixement de la narració gràfica com una forma d’expressió artística que, a l’igual que la literatura, ha de ser analitzada i treballada des de les aules universitàries, ja que ens pot beneficiar en l’ensenyament de molts àmbits d’investigació. Gràcies a Unicòmic, a la Universitat d’Alacant les vinyetes han deixat de considerar-se una distracció juvenil per a considerar-se una forma d’art equiparable a la literatura.

Synthetic scope and DFT analysis of the chiral binap-gold (I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

The 1,3-dipolar cycloaddition between glycine-derived azlactones with maleimides is efficiently catalyzed by the dimeric chiral complex [(Sa)-Binap·AuTFA]2. The alanine-derived oxazolone only reacts with tert-butyl acrylate giving anomalous regiochemistry, which is explained and supported by Natural Resonance Theory and Nucleus Independent Chemical Shifts calculations. The origin of the high enantiodiscrimination observed with maleimides and tert-butyl acrylate is analyzed using DFT computed at M06/Lanl2dz//ONIOM(b3lyp/Lanl2dz:UFF) level. Several applications of these cycloadducts in the synthesis of new proline derivatives with a 2,5-trans-arrangement and in the preparation of complex fused polycyclic molecules are described.