C-C Bond formation catalyzed by natural gelatin and collagen proteins

The activity of gelatin and collagen proteins towards C–C bond formation via Henry (nitroaldol) reaction between aldehydes and nitroalkanes is demonstrated for the first time. Among other variables, protein source, physical state and chemical modification influence product yield and kinetics, affording the nitroaldol products in both aqueous and organic media under mild conditions. Significantly, the scale-up of the process between 4-nitrobenzaldehyde and nitromethane is successfully achieved at 1 g scale and in good yield. A comparative kinetic study with other biocatalysts shows an increase of the first-order rate constant in the order chitosan < gelatin < bovine serum albumin (BSA) < collagen. The results of this study indicate that simple edible gelatin can promote C–C bond forming reactions under physiological conditions, which may have important implications from a metabolic perspective

Synthesis of new conformationally rigid phenylalanine analogues

The reactivity of (Z)-2-phenyl-4-benzylidene-5(4H)-oxazolone 1 as dienophile in the Diels-Alder reaction with 1,3-butadiene and 2,3-dimethyl-1,3-butadiene is studied. The adducts obtained starting from the cycloaddition of 1 with both dienes are converted, through simple reactions into the conformationally restricted cyclic amino acids cis-1-amino-2-phenylcyclohexanecarboxylic acid 6 and 1-amino-c-4,c-5-dimethyl-t-2-phenyl-r-1-cyclohexanecarboxylic acid 10, analogues of phenylalanine.We are indebted to the generous support of the Dirección General de Investigación Científica y Técnica, project PB91-0696.Peer reviewe

Synthesis of the four d,l-pairs of 2-amino-3-phenylnorbornane-2-carboxylic acids. II. The use of 5(4H)-oxazolones as dienophiles

The Diels-Alder reaction between both geometric isomers (Z)- or (E)-2-phenyl-4-benzylidene-5(4H)-oxazolone and cyclopentadiene is studied. The cycloadducts are converted into the aminoacids through simple reactions allowing the synthesis of the four d,l-pairs of 2-amino-3-phenylnorbornane-2-carboxylic acids.We are indebted to the generous support of the Dirección General de Investigación Científica y Técnica, projects PB88-0038 and PB91-0696Peer reviewe

On the synthesis of 3(5)-carbomethoxy-4-hetarylpyrazoles

3(5)-Carbomethoxy-4-hetarylpyrazoles 3 can be obtained by the aromatization of the corresponding cis-3-benzamido-3-carbomethoxy-4-hetaryl-Δ1-pyrazolines 2 obtained by 1,3-dipolar cycloaddition of diazo-methane with methyl Z-2-benzamido-3-hetarylpropenoates 1. An explanation, based on FMO theory, for the different reactivity of the dipolarophiles with diazomethane is given.Peer reviewe

β-turn modulation by the cyclohexane analogues of phenylalanine

X-ray diffraction experiments have evidenced that the orientation of the aromatic side chain determine the folding tendencies of (t)BuCO-Pro-c6Phe- NH(i)Pr, where c6Phe denotes tire (S,S) and (R,R) cyclohexane analogues of phenylalanine. In the solid state, both dipeptides are β-folded, the β- turn type being dictated by the stereochemistry of the cyclohexane ring.Peer reviewe

Aspartame analogues containing 1-amino-2-phenylcyclohexanecarboxylic acids (c6Phe)

This report describes the synthesis and the conformational analysis of the optically pure dipeptides analogues of aspartame: H-(S)-Asp-(1R,2R)-c6Phe-OMe and H-(S)-Asp-(1S,2S)-c6Phe-OMe, in which the Phe residue of aspartame has been replaced by a restricted Phe with a cyclohexane skeleton: 1-amino-2-phenylcyclohexanecarboxylic acid (c6Phe). Of these, only the dipeptide that incorporates (1R,2R)-c6Phe is sweet, whereas that incorporates (1S,2S)-c6Phe is bitter. This relationship between the absolute configuration of the dipeptides and the properties is explained through the different conformational behaviour displayed by each molecule, based on molecular mechanics and molecular dynamics calculations, including solvent effects.This work has been supported by the Ministerio de Ciencia y Tecnologı́a (project PPQ2001-1305), Universidad de La Rioja (project API-01/B02), Diputación General de Aragón (project P22/98), PETRI (PTR95/0422-OP) and Productos Aditivos S. A.Peer reviewe

Propuesta didáctica para la enseñanza de las actividades físicas en el medio natural mediante las TIC: senderismo

Este artículo recoge una experiencia vivenciada por alumnos universitarios, centrada en la aplicación práctica de la realidad aumentada (nivel de iniciación, mediante códigos QR) en el ámbito de las actividades físicas deportivas en el medio natural. El objetivo de nuestra propuesta es emular una salida de senderismo propia de un centro de Educación Primaria con la aplicación de las TIC. Mediante este procedimiento permitimos a nuestros alumnos acceder a información sobre el entorno que les rodea de una forma interactiva y motivadora. Se han incluido aspectos culturales, conocimiento de la fauna y de la flora, normativa de educación vial y la propia ruta a completar. La experiencia ha resultado satisfactoria para todos los participantes, encontrando una aplicabilidad real para su futura actividad docente. This article summarizes the experience that a group of student teachers had: the use of QR codes to present a magnified reality during Physical Education activities (in this case, hiking). The purpose of such experience was to emulate an approppiate Primary School environmental fieldtrip with a practical application of ICT. Students were motivated to Access knowledge about the natural environs by means of interaction: contents such as place cultural aspects, fauna and flora, road safety and the route intself were included in the QR codes. The experience was very satisfactory to all participants. They found it certainly feasible for future teaching activities

Natural amino acids as chiral auxiliaries in asymmetric Diels-Alder reactions

To test whether a-amino acids can be efficient chiral auxiliaries in asymmetric Diels-Alder reactions, the chiral dienophile N-acryloyl-L-phenylalanine methyl ester was made to react with cyclopentadiene. Diastereofacial selectivity is to a great extent dependent on the Lewis acid used to promote the reaction; whereas moderate excesses of the (1 R, 2R)-cycloadduct were achieved with AlC13, the reaction did not show diastereofacial selectivity when titanium catalysts were used. Moreover, with T~('PI-(I)4a transesterification reaction, which leads to the isopropyl ester and competes with the Diels-Alder reaction, was observed. In spite of the structural similarity of this dienophile to the acrylate of (S)-ethyl lactate, it behaved very differently in the titanium-catalyzed reactions.This research was made possible by the generous financial support of the Comisión Asesora de Investigación Cientifica y Técnica (project number PB85-0335). Maria P. Bueno would like to express her gratitude to the Diputación General de Aragón and Paula Charro to the Instituto de Estudios Riojanos for a grant.Peer reviewe

Stereoselective synthesis of 1,3-diaminotruxillic acid derivatives: an advantageous combination of C-H-ortho-palladation and on-flow [2+2]-photocycloaddition in microreactors

The stereoselective synthesis of ε-isomers of dimethyl esters of 1,3-diaminotruxillic acid in three steps is reported. The first step is the ortho-palladation of (Z)-2-aryl-4-aryliden-5(4H)-oxazolones 1 to give dinuclear complexes 2 with bridging carboxylates. The reaction occurs through regioselective activation of the ortho-C-H bond of the 4-arylidene ring in carboxylic acids. The second step is the [2+2]-photocycloaddition of the C-C exocyclic bonds of the oxazolone skeleton in 2 to afford the corresponding dinuclear ortho-palladated cyclobutanes 3. This key step was performed very efficiently by using LED light sources with different wavelengths (465, 525 or 625 nm) in flow microreactors. The final step involved the depalladation of 3 by hydrogenation in methanol to afford the ε-1,3-diaminotruxillic acid derivatives as single isomers.Funding by the Ministerio de Economia y Competitividad (MINECO) (Spain, Projects CTQ2011-22589, CTQ2011-22410 and CTQ2013-40855-R, CTQ2014-54987-P) and Gobierno de Aragón-Fondo Social Europeo (Spain, groups E40 and E97) is gratefully acknowledged. M.V.G. thanks the Ministerio de Economia y Competitividad (Spain) for funding her contract through the Ramón y Cajal program and Parque Científico y Tecnológico de Castilla-La Mancha.Peer Reviewe

Stereoselective Synthesis of 1,3-Diaminotruxillic Acid Derivatives: An Advantageous Combination of C[BOND]H-ortho-Palladation and On-Flow [2+2]-Photocycloaddition in Microreactors

The stereoselective synthesis of ε-isomers of dimethyl esters of 1,3-diaminotruxillic acid in three steps is reported. The first step is the ortho-palladation of (Z)-2-aryl-4-aryliden-5(4H)-oxazolones 1 to give dinuclear complexes 2 with bridging carboxylates. The reaction occurs through regioselective activation of the ortho-C[BOND]H bond of the 4-arylidene ring in carboxylic acids. The second step is the [2+2]-photocycloaddition of the C[DOUBLE BOND]C exocyclic bonds of the oxazolone skeleton in 2 to afford the corresponding dinuclear ortho-palladated cyclobutanes 3. This key step was performed very efficiently by using LED light sources with different wavelengths (465, 525 or 625 nm) in flow microreactors. The final step involved the depalladation of 3 by hydrogenation in methanol to afford the ε-1,3-diaminotruxillic acid derivatives as single isomers.Funding by the Ministerio de Economia y Competitividad (MINECO) (Spain, Projects CTQ2011-22589, CTQ2011-22410 and CTQ2013-40855-R, CTQ2014-54987-P) and Gobierno de Aragón-Fondo Social Europeo (Spain, groups E40 and E97) is gratefully acknowledged. M.V.G. thanks the Ministerio de Economia y Competitividad (Spain) for funding her contract through the Ramón y Cajal program and Parque Científico y Tecnológico de Castilla-La Mancha