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http://hdl.handle.net/10261/81
2015-09-01T03:58:34ZProperties of Cationic Pnicogen-Bonded Complexes F4–nHnP+:N-Base with F–P···N Linear and n = 0–3
http://hdl.handle.net/10261/117719
Título : Properties of Cationic Pnicogen-Bonded Complexes F4–nHnP+:N-Base with F–P···N Linear and n = 0–3
Autor : Bene, J. E. del; Alkorta, Ibon; Elguero, José
Resumen: Ab initio MP2/aug′-cc-pVTZ calculations were performed to investigate the pnicogen-bonded complexes F<inf>4-n</inf>H<inf>n</inf>P<sup>+</sup>:N-base, for n = 0-3, each with a linear or nearly linear F-P⋯N alignment. The nitrogen bases include the sp<sup>3</sup> bases NH<inf>3</inf>, NClH<inf>2</inf>, NFH<inf>2</inf>, NCl<inf>2</inf>H, NCl<inf>3</inf>, NFCl<inf>2</inf>, NF<inf>2</inf>H, NF<inf>2</inf>Cl, and NF<inf>3</inf> and the sp bases NCNH<inf>2</inf>, NCCH<inf>3</inf>, NP, NCOH, NCCl, NCH, NCF, NCCN, and N<inf>2</inf>. The binding energies vary between -20 and -180 kJ·mol<sup>-1</sup>, while the P-N distances vary from 1.89 to 3.01 Å. In each series of complexes, binding energies decrease exponentially as the P-N distance increases, provided that complexes with sp<sup>3</sup> and sp hybridized bases are treated separately. Different patterns are observed for the change in the binding energies of complexes with a particular base as the number of F atoms in the acid changes. Thus, the particular acid-base pair is a factor in determining the binding energies of these complexes. Three different charge-transfer interactions stabilize these complexes. These arise from the nitrogen lone pair to the σ∗P-F<inf>ax</inf>, σ∗P-F<inf>eq</inf>, and σ∗P-H<inf>eq</inf> orbitals. The dominant single charge-transfer energy in all complexes is N<inf>lp</inf> → σ∗P-F<inf>ax</inf>. However, since there are three N<inf>lp</inf> → σ∗P-F<inf>eq</inf> charge-transfer interactions in complexes with F<inf>4</inf>P<sup>+</sup> and two in complexes with F<inf>3</inf>HP<sup>+</sup>, the sum of the N<inf>lp</inf> → σ∗P-F<inf>eq</inf> charge-transfer energies is greater than the N<inf>lp</inf> → σ ∗P-F<inf>ax</inf> charge-transfer energies in the former complexes, and similar to the N<inf>lp</inf> → σ ∗P-F<inf>ax</inf> energies in the latter. The total charge-transfer energies of all complexes decrease exponentially as the P-N distance increases. Coupling constants <sup>1p</sup>J(P-N) across the pnicogen bond vary with the P-N distance, but different patterns are observed for complexes with F<inf>4</inf>P<sup>+</sup> and complexes of the sp<sup>3</sup> bases with F<inf>3</inf>HP<sup>+</sup>. These initially increase as the P-N distance decreases, reach a maximum, and then decrease with decreasing P-N distance as the P⋯N bond acquires increased covalent character. For the remaining complexes, <sup>1p</sup>J(P-N) increases with decreasing P-N distance. Complexation increases the P-F<inf>ax</inf> distance and <sup>1</sup>J(P-F<inf>ax</inf>) relative to the corresponding isolated ion. <sup>1</sup>J(P-F<inf>ax</inf>) correlates quadratically with the P-N distance.2015-07-08T09:54:59ZImidazole-containing phthalazine derivatives inhibit Fe-SOD performance in Leishmania species and are active in vitro against visceral and mucosal leishmaniasis
http://hdl.handle.net/10261/117717
Título : Imidazole-containing phthalazine derivatives inhibit Fe-SOD performance in Leishmania species and are active in vitro against visceral and mucosal leishmaniasis
Autor : Sánchez-Moreno, M.; Gómez-Contreras, F.; Navarro, Pilar; Marín, C.; Ramírez-Macías, Inmaculada; Rosales, M. J.; Campayo, Lucrecia; Cano, C.; Sanz, A. M.; Yunta, M. J. R.
Resumen: The in vitro leishmanicidal activity of a series of imidazole-containing phthalazine derivatives 1-4 was tested on Leishmania infantum, Leishmania braziliensis and Leishmania donovani parasites, and their cytotoxicity on J774·2 macrophage cells was also measured. All compounds tested showed selectivity indexes higher than that of the reference drug glucantime for the three Leishmania species, and the less bulky monoalkylamino substituted derivatives 2 and 4 were clearly more effective than their bisalkylamino substituted counterparts 1 and 3. Both infection rate measures and ultrastructural alterations studies confirmed that 2 and 4 were highly leishmanicidal and induced extensive parasite cell damage. Modifications to the excretion products of parasites treated with 2 and 4 were also consistent with substantial cytoplasmic alterations. On the other hand, the most active compounds 2 and 4 were potent inhibitors of iron superoxide dismutase enzyme (Fe-SOD) in the three species considered, whereas their impact on human CuZn-SOD was low. Molecular modelling suggests that 2 and 4 could deactivate Fe-SOD due to a sterically favoured enhanced ability to interact with the H-bonding net that supports the antioxidant features of the enzyme.2015-07-08T09:42:49ZDivergent, stereoselective access to heterocyclic α,α-quaternary- and β<sup>2,3,3</sup>-amino acid derivatives from a N-Pmp-protected Orn-derived β-lactam
http://hdl.handle.net/10261/117703
Título : Divergent, stereoselective access to heterocyclic α,α-quaternary- and β<sup>2,3,3</sup>-amino acid derivatives from a N-Pmp-protected Orn-derived β-lactam
Autor : Núñez-Villanueva, D.; García López, María Teresa; Martín Martínez, María Mercedes; González-Muñiz, Rosario
Resumen: A suitably protected Orn-derived (3S,4S)-β-lactam was used as common intermediate in the synthesis of conformationally constrained (3S,4S)-2-oxoazepane α,α- and (2S,3S)-2-oxopiperidine-β<sup>2,3,3</sup>-amino acid derivatives. Compared to alternative procedures using an N-p-methoxybenzyl group at the 2-azetidinone, the incorporation of a p-methoxyphenyl moiety is crucial for the excellent stereochemical outcomes in the preparation of these heterocyclic amino acids. Chemoselective 7- or 6-exo-trig cyclization was achieved through alternative sequences of Pmp-deprotection/Boc-activation, followed by inter- and intramolecular β-lactam ring opening, respectively.2015-07-08T08:46:07Z1,2-stereochemical induction in the Pd<sup>II</sup>-catalyzed conjugate addition of boronic acids
http://hdl.handle.net/10261/117697
Título : 1,2-stereochemical induction in the Pd<sup>II</sup>-catalyzed conjugate addition of boronic acids
Autor : Roscales, S.; Sánchez, Francisco; Csákÿ, Aurelio G.
Resumen: Palladium(II) catalysis has been used in the substrate-controlled 1,2-chiral induction of the conjugate addition of boronic acids to enantiopure α,β-unsaturated ketones and esters without competition from the Mirozoki-Heck reaction. Bedford's palladacycle was found to control the stereoselectivity without the need for additional chiral ligands. We report that the Pd<sup>II</sup>-catalyzed conjugate addition reaction between boronic acids and acyclic ketones or esters that bear a hydroxyl substituent at their γ-position (glyceraldehyde derivatives) can afford high levels of anti stereoselection, comparable to those reported previously using more expensive Rh<sup>I</sup> catalysts. On the other hand, high levels of syn stereoselectivity were observed with acyclic esters that bear an amino substituent at their γ-position (serine derivatives). In this case, the levels of stereoselection could be enhanced by using cyclic derivatives derived from Garner's aldehyde.2015-07-08T08:06:45Z