Chemistry - A European Journal最新文献

This article describes the synthesis of a difluorinated CinNapht derivative in the 4' and 5' positions allowing the easy access to two new families of fluorophores by late-stage functionalization using SNAr. The first one comprises derivatives incorporating hindered aromatic amines in the 4' and 5' positions, which show redemission in apolar solvents. The second one is obtained through the use of dinucleophiles. Among them, Tetrahydroquinoxaline (THQ) and tetrahydrobenzodiazepine (THB) compounds show strongly redshifted emission. The photophysical properties of all the fluorophores in these two families are studied and rationalized by DFT and TDDFT calculations. The most promising compounds have been used to image living cells by confocal microscopy.

This study presents efficient synthetic pathways for preparing novel azaspirocycles. These methodologies involve functionalizing key bicyclic hydrazines with a substituent on one of their bridgehead carbon atoms. The desired spirocyclic cores were successfully obtained through double reductive amination reactions, intramolecular cyclizations, and cleavages of the N-N bond. The isolated molecules possess unique three-dimensional structures, suggesting potential applications in medicinal chemistry and drug discovery. With the growing interest in targeting nucleic acids as a complementary approach to protein-targeting strategies for developing novel active compounds, we investigated the potential of the synthesized azaspirocycles as RNA binders. As a proof of concept, we highlight the promising activity of some compounds as strong binders of HIV-1 TAR RNA and inhibitors of Tat/TAR interactions.

Pseudomonas aeruginosa is a prevalent opportunistic human pathogen, particularly associated with cystic fibrosis. Among its virulence factors are the LecA and LecB lectins. Both lectins play an important role in the adhesion to the host cells and display cytotoxic activity. In this study, we successfully synthesized hardly hydrolysable carbohydrate ligands targeting these pathogenic lectins, including two bispecific glycans. The interactions between LecA/LecB lectins and synthetic glycans were evaluated using hemagglutination (yeast agglutination) inhibition assays, comparing their efficacy with corresponding monosaccharides. Additionally, the binding affinities of bispecific glycans were assessed using isothermal titration calorimetry (ITC). Structural insight into the lectin-ligand interaction was obtained by determining the crystal structures of LecA/LecB lectins in complex with one of the bispecific ligands using X ray crystallography. This comprehensive investigation into the inhibitory potential of synthetic glycosides against P. aeruginosa lectins sheds light on their potential application in antimicrobial therapy.

The Cover Feature shows artificial photosynthesis to convert H₂O vapour/CO₂ into the value-added chemical CH₄. Intermediate temperature-sensitive Ti−H species are generated by the photosensitized PDI dye component of the Pt/N−TiO₂/PDI composite catalyst; this enables incident light energy that has relaxed into waste heat to locally heat a highly nucleophilic hydride for CO₂ addition to a COOH* intermediate. (Until now it had been thought that photocatalysis and temperature were almost negatively dependent.) Shown top left is the photoexcitation process by which electrons are transferred to the TiO₂ surface to generate Ti−H species; this converts 53 % of the relaxed incident light into a thermal effect to be re-used. Shown top right is the acceleration of the reaction rate through increasing the initial energy of the rate-limiting step as the catalyst surface temperature increases and it becomes easier to cross the activation barrier. More information can be found in the Research Article by D. Ma, H. Ji, W. Ma, and co-workers (DOI: 10.1002/chem.202402102).

The development of stable high-performance n-type organic semiconductors for applications in organic field-effect transistors (OFETs) under ambient conditions is desirable but challenging. To address this issue, we here synthesized a series of functionalized-phenanthrene conjugated asymmetric N-heteroacenes, where the phenanthrene moiety was modified by N substitution or Br functionalization at different positions to induce various degrees of asymmetry in their structures. The photophysical and electrochemical properties of these molecules were studied, and their packing patterns were analysed. The OFETs based on these materials were fabricated through simple spin-coating method, and the as-resulted thin films were treated with different conditions. The devices exhibit typical n-type performances under ambient conditions with charge carrier mobilities up to 4.27 × 10-3 cm2 V-1 s-1. The crystallinities and morphologies of these thin films were studied to investigate the correlations between the device performances and thin-film characteristics. Our study suggests that phenanthrene conjugated N-heteroacenes can be developed as promising air-stable solution-processable n-type semiconducting materials, and Br modification at certain positions of phenanthrene is beneficial in adjusting the thin-film properties for the improvement of OFET performances.

A pivaloyl-protected triangular tris-resorcinarene—a synthetic macrocycle consisting of three protected resorcinarene units linked by six pentylene chains—adopts open and closed conformations in solution. The open–closed conformation equilibrium is solvent-dependent. Shape-complementary solvent molecules facilitate solvation of the cavity interior to promote the open conformation, whereas the closed conformation is preferred in solvent molecules that are not complementary to the cavity interior. The cover image shows two conformers. More information can be found in the Research Article by T. Haino and co-workers (DOI: 10.1002/chem.202402922).

Controlled pore glass (CPG), differing in pore size and subsequent specific surface, was chemically modified by: (1) increasing surface susceptibility for amine functionalization via reaction with oxirane-type (active) and alkyl/aryl-type (inactive towards amine compounds) silane pro-adhesive compounds, and (2) immobilization of trimethylolpropane tris[poly(propylene glycol), amine terminated] ether, comb-like 8-arm octa[poly(ethylene glycol) amine] with each branch amine terminated, and a poly(propylene imine) amine-terminated second-generation dendrimer. The increase in surface density of amine functions-monitored by UV-Vis technique adopted for quantitative measurements of Ruhemann's purple intensity-improved final loading capacity, characterized by dimethoxytrityl cation absorption. Obtained materials proved their applicability in automatic oligonucleotide (ON) synthesis, especially when silanized 2000 Å CPG modified with 8-arm octa[poly(ethylene glycol) amine], with deduced empirical formula CPG-silane-(NH)5.7PEG-(NH2)2.3, was used for long-chain (150 nucleotides) ONs synthesis. This can be regarded as a good CPG support for this purpose. Moreover, hybrid supports with different porosity allowed the synthesis of shorter ONs with satisfactory yield and purity, monitored by RP-HPLC and MALDI-TOF. On the molecular level, two competitive mechanisms seem to influence the utility of the final hybrid support: spatial availability of active sites and the propensity of the functionalizer to bond with the CPG surface.

The pre-association mechanism of an ion-pair Type II photoinitiating system (PIS) acting in the visible range was studied. The choice of a dye as photoinitiator (crystal violet) with an excited state lifetime of 200 ps ensured the absence of dynamical quenching by the borate salts used as coinitiators. In spite of the fact that no diffusional bimolecular quenching can take place, excellent polymerization efficiency was found, underlining the high reactivity of the PIS. A saturation effect is observed when increasing the concentration of borate as a consequence of the pre-association mechanism arising from coulombic interaction between the cationic dye and the anionic coinitiator. The association equilibria of the system were described and the corresponding association constant values were calculated, allowing to quantify the pre-association efficiency. This was further successfully correlated to the observed maximal rates of polymerization. The efficiency of this super-stoichiometric sample with an excess of borate was finally compared to the stoichiometric 1:1 dye:borate ion-pair. It is shown that the pre-association mechanism could lead to much higher efficiency than the stoichiometric ion-pair.

Both enantiomers of functionalized Hajos-Parrish ketone (HPK) analogs were prepared with excellent diastereoselectivities and enantioselectivities using the same chiral catalyst under two slightly different conditions. In condition A, dioxane was used as the solvent with 3 equivalents of water. In condition B, acetonitrile was used as the solvent with 30 equivalents of water, followed by epimerization with a base in a one-pot. The reaction consisted of a domino reaction including a diphenylprolinol silyl ether-mediated asymmetric Michael reaction and an intramolecular Henry reaction. In the Michael reaction, depending on the solvent and water amounts, syn- and anti-isomers were selectively synthesized with excellent enantioselectivity, in which the absolute configuration at C5 (indanone numbering) was opposite. The subsequent Henry reaction was diastereoselective, in which the C5 substituent controlled the three chiral centers in a highly diastereoselective manner. The final base treatment in condition B caused epimerization, changing the stereochemistry at C6. Switching more than two chiral centers with high enantioselectivity is extremely difficult using the same chiral catalyst; the present reaction is a very rare enantiodivergent reaction that switches five continuous chiral centers with high enantioselectivity.

A group of four white discs at the center of the Othello board represents the pyridine rings of the complex [Rh(N^N)₂]⁺. The complex undergoes rollover cyclometallation of one of the pyridine rings to afford [Rh(N^N)(C^N)(H)(CH₃OH)]⁺, [Rh(N^N)(N^C)(H)(CH₃OH)]⁺, [Rh(C^N)(N^N)(H)(CH₃OH)]⁺, or [Rh(N^C)(N^N)(H)(CH₃OH)]⁺ at the same probability, which are represented as groups of one black disc and three white discs. Upon irradiation (white beam), every black disc turns over to return to the group of four white discs. More information can be found in the Research Article by K. Shinozaki and co-workers (DOI: 10.1002/chem.202402067).