Crystal structure of the N-benzyloxycarbonyl-Alanyl-Phenylalanyl-methyl ester: the importance of the H-bonding pattern

Large crystals of the methyl ester of the N-a-benzyloxycarbonyl protected Ala-Phe dipeptide (Z-AF-OMe) were obtained after the very slow evaporation of a solution of the corresponding carboxylic acid (Z-AF-OH) in methanol containing an excess of HCl. The structure was confirmed by single crystal X-ray diffraction data. It crystallizes in the orthorhombic space group P212121 with unit cell dimensions a = 5.0655(6) Å, b = 8.4614(8) Å, c = 46.856(5) Å, V = 2008.3(4) Å3, Z = 4. In the crystal, the molecules form hydrogen bonded chains running along the a axis of the unit cell. Other secondary interactions are also discussed

3-Allyl-6-bromo-1H-imidazo[4,5-b]pyridin-2(3H)-one

In the title compound, C15H14N2O4, (I), the mol­ecule lies on a twofold rotation axis which passes through the central C atom of the aliphatic chain, giving one half-mol­ecule per asymmetric unit. The structure is a monoclinic polymorph of the triclinic structure previously reported [Brito, Vallejos, Bolte & López-Rodríguez (2010). Acta Cryst. E66, o792], (II). The most obvious difference between them is the O/C/C/C—O/C/C/C torsion angle [58.2 (7)° in (I) and 173.4 (3)/70.2 (3)° in (II) for GG and TG conformations, respectively]. Another important difference is observed in the dihedral angle between the planes of the aromatic rings [86.49 (7)° for (I) and 76.4 (3)° for (II)]. The crystal structure features a weak π–π inter­action [centroid–centroid distance = 4.1397 (10)Å]; this latter kind of inter­action is not evident in the triclinic polymorph

Cooperative Education in Green Chemistry: The Spanish Experience

A common postgraduate training in Green Chemistry is currently being carried out by several Spanish universities. This initiative considers the corresponding Máster and PhD programs in Sustainable Chemistry and has been successfully achieved with the participation of experts from different Universities and Research Institutions grouped within the coverage of the Spanish Network on Sustainable Chemistry (REDQS). A cooperative effort and a modular design are the key elements that have allowed maintaining the Spanish Interuniversity Máster and PhD programs for more than a decade, providing a high level of quality and a unique possibility, for many students, of being trained at an advanced level in Green Chemistry

1-Decyl-6-nitro-1H-benzimidazol-2(3H)-on

The title mol­ecule, C17H25N3O3, is built up from fused six- and five-membered rings linked to a –C10H21 chain. The fused-ring system is essentially planar, the largest deviation from the mean plane being 0.009 (2) Å. The chain is roughly perpendic­ular to this plane, making a dihedral angle of 79.5 (2)°. In the crystal, N—H[cdots, three dots, centered]O hydrogen bonds build infinite chains along [010]. There are channels in the structure containing disordered hexane. The contribution of this solvent to the scattering power was suppressed using the SQUEEZE option in PLATON [Spek (2009 [triangle]). Acta Cryst. D65, 148–155]

Macrocycle Synthesis by Chloride-Templated Amide Bond Formation

A new family of pseudopeptidic macrocyclic compounds has been prepared involving an anion-templated amide bond formation reaction at the macrocyclization step. Chloride anion was found to be the most efficient template in the macrocyclization process, producing improved macrocyclization yields with regard to the nontemplated reaction. The data suggest a kinetic effect of the chloride template, providing an appropriate folded conformation of the openchain precursor and reducing the energy barrier for the formation of the macrocyclic product.This work was supported by the Spanish Ministry of Science and Innovation (CTQ2012-38543-C03) and Generalitat Valenciana (PROMETEO/2012/020). V.M.-C. thanks Generalitat Valenciana for a postdoctoral fellowship (APOSTD/ 2013/041)

Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State

Several kinetic models for the macrocyclization of a C2 pseudopeptide with a dihalide through a SN2 reaction have been developed. These models not only focus on the kinetic analysis of the main macrocyclization reaction, but also consider the competitive oligomerization/polymerization processes yielding undesired oligomeric/polymeric byproducts. The effect of anions has also been included in the kinetic models, as they can act as catalytic templates in the transition state reducing and stabilizing the transition state. The corresponding differential equation systems for each kinetic model can be solved numerically. Through a comprehensive analysis of these results, it is possible to obtain a better understanding of the different parameters that are involved in the macrocyclization reaction mechanism and to develop strategies for the optimization of the desired processes

Supramolecular protection from the enzymatic tyrosine phosphorylation in a polypeptide

Here we report two new artificial pseudopeptidic cages that bind the EYE peptide epitope in pure water at physiological pH (as studied by fluorescence and NMR spectroscopies). The supramolecular complexation of the Tyr residues efficiently precludes their subsequent PTK-catalysed phosphorylation. Our results show a supramolecular modulation of the PTK activity by competitive substrate caging.This work was supported by MINECO/FEDER (CTQ2012-38543-C03, CTQ2015-68429-R and CTQ2015-70117-R projects) and Generalitat de Catalunya (AGAUR, 2014 SGR 231)

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

Positive effects of the polymeric support on the performance of supported chiral catalysts, in terms of activity, stability and selectivity–enantioselectivity, have been reported when the support is properly selected and optimized opening the way to the design of more efficient catalytic systems

Synthesis of new fluorescent pyrylium dyes and study of their interaction with N-protected amino acids

Six new 6-styryl-2,4-diarylpyrylium salts have been synthesized and fully characterized by means of 1H/13C NMR, HRMS, UV-vis and Steady-State/Time-Resolved Fluorescence spectroscopies. This set of molecules is composed of a core pyrylium fluorophore, an amino acid (valine or phenylalanine), and an alkylic chain of variable length. The emissive properties (fluorescence quantum yields and lifetimes and radiative deactivation rate constants) in dichloromethane, acetonitrile and PBS have been recorded. The interaction of these pyrylium salts with aminoacids in their N-protected forms has been studied by means of fluorescence quenching, using the Stern–Volmer methodology. It has been found that dynamic (collisional) quenching is the most prevalent process for all the fluorescent molecules, irrespective of the amino acid building block or the length of the alkyl chain. The emission of the pyrylium molecules is strongly quenched by Z-Trp-OH and to a lesser extent by Z-Tyr-OH and Z-Met-OH and no quenching was measured with Z-Ala-OH, Z-Val-OH and Z-Phe-OH. A small degree of ground-state complexation was observed for receptor 8a and by Z-Trp-OH (upward curvature in the Stern–Volmer plot). Complementary 1H-NMR titrations demonstrated the existence of such a weak ground state complex