Enantioselective synthesis of proline derivatives by 1,3-dipolar cycloadditions

Research devoted to the synthesis of highly substituted prolines, which are hepatitis C virus inhibitors, using 1,3-dipolar cycloadditions (1,3-DC) of azomethine ylides is described. In the first part, a diastereoselective approach using an inexpensive lactate-derived acrylate as dipolarophile is described. In the second part, our efforts using simple and easily accessible chiral silver(I) and gold(I) complexes as catalysts for enantioselective synthesis of proline derivatives are reviewed. In this case, chiral phosphoramidites and binap have been used as privileged ligands. Parallel to these experimental results, considerable effort was dedicated to run semiempirical density functional theory (DFT) calculations to explain and justify the stereoselectivity of each process.This work has been supported by the DGES of the Spanish Ministerio de Ciencia e Innovación (MICINN) (Consolider INGENIO 2010 CSD2007-00006, FEDER-CTQ2007-62771/BQU, and by the Hispano-Brazilian project PHB2008-0037-PC), Generalitat Valenciana (PROMETEO/2009/039), and by the University of Alicante (GITE-09020-UA)

Chemisorption of group-III metals on the Si(111) and Ge(111) surfaces: An ab initio study

Chemisorption of group-III metal adatoms on Si(111) and Ge(111) has been studied through the ab initio Hartree-Fock method including nonempirical pseudopotentials and using cluster models to simulate the surface. Three different high-symmetry sites (atop, eclipsed, and open) have been considered by using X4H9, X4H7, and X6H9 (X=Si,Ge) cluster models. In a first step, ideal surface geometries have been used. Metal-induced reconstruction upon chemisorption has also been taken into account. Equilibrium distances, binding energies, and vibrational frequencies have been obtained and compared with available experimental data. From binding-energy considerations, the atop and eclipsed sites seem to be the most favorable ones and thus a coadsorption picture may be suggested. Group-III metals exhibit a similar behavior and the same is true for Si(111) and Ge(111) surfaces when chemisorption is considered