ChemistryEurope最新文献

Front Cover picture illustrates the merging of mechanics and chemistry to produce molecules of interest. The synthesis of peptides by flow mechanochemistry was performed in a twin-screw extruder (TSE) used as a chemical reactor. In their Research Article, T. M. El-Dine, T.-X. Métro, F. Lamaty, and co-workers describe how applications of screw-generated mechanical forces to a mixture of amino acids and coupling agents delivered to the top of a TSE barrel promoting the synthesis of the corresponding peptide—in this case, aspartame—recovered from the die of the TSE. Various peptides were synthesized by this method. The artwork was designed my by Marcelin Lamaty.

An elusive T-shaped high-valent Cu^III derivative, Cu(CF₃)₃ which is depicted on the cover, was stabilized in the form of solvates and theoretically studied. In their Research Article, V. Motornov, X. Ribas, P. Beier, and co-workers report the synthesis of solvates Cu(CF₃)₃⋅2DMF and Cu(CF₃)₃⋅MeCN, which were fully characterized including X-ray crystallography. Ligand substitution in these solvates enables access to a variety of new high-valent Cu^III complexes. The authors would like to thank Tomáš Belloň for creating the artwork.

The factors controlling the activation of σ-bonds promoted by hidden Frustrated Lewis Pairs have been computationally explored using quantum chemical tools. To this end, the influence of both the nature of the group 13 element acting as Lewis acid as well as the cooperative action of the Lewis antagonists on the bond activation was quantitatively analyzed by means of the activation strain model of reactivity in combination with the energy decomposition analysis method. It is found that while the activation of the polar E^X−H bonds (E¹⁵=group 15 element; E¹⁶=group 16 element) is feasible, the analogous processes involving non-polar E¹⁴−H bonds (CH₄, SiH₄ or H₂) proceed with much higher barriers. Nevertheless, these processes, and in particular the dihydrogen activation, can be realizable (i. e. proceeding with a feasible barrier) through rational design.

A method was developed that enables the magnesium chloride (MgCl₂)-activated S-acetamidomethyl cysteine sulfoxide (Cys(Acm)(O)) to induce the sp²(C−H) sulfenylation of the indole of Trp residues. The reaction operates under mild acidic conditions using acetic acid or an ionic liquid to give the Trp-sulfenylated products. Other than Trp, all other proteinogenic amino acids are unreactive to the sulfenylation conditions. We demonstrated the successful application of this reaction to various peptides, including lysozyme. Furthermore, we achieved the Trp-modification of a monoclonal antibody by a MgCl₂-mediated reaction in an acidic ionic liquid. The resulting antibody exhibited antibody performance comparable to the parent protein. The amide moiety in the Acm group contributes to the difference in chemical behaviors between S-Acm and S-p-methoxybenzyl (MBzl)-protected cysteine sulfoxides. This is because the S-Acm sulfoxide is converted to S-chlorocysteine responsible for Trp-sulfenylation under less acidic conditions than those required for the reaction of S-MBzl sulfoxide. Based on this rationale, we prepared a linker possessing S-Acm and S-MBzl oxide moieties and subjected the linker to heterodimerization of DNA-binding MYC and MAX peptides containing a Trp handle. The one-pot/stepwise Cys-Trp conjugation between the linker and DNA-binding peptides allowed the generation of a heterodimeric MYC/MAX DNA binder.

In supramolecular chemistry, the pursuit of highly efficient molecular recognition systems holds paramount significance. This study introduces new [2.2]paracyclophanes (PCP) as exceptional guest molecules for cucurbit[8]uril (CB8). This well-matched host-guest interaction is marked by ultra-high binding affinities (K_a up to 10¹⁵ M⁻¹ in water) accompanied by unprecedented exothermic contributions (ΔH up to −20.6 kcal mol⁻¹) observed in CB8 binding, rivaling the exceptional affinities of cucurbit[7]uril (CB7), which has until now been recognized as the gold standard for high-affinity binding in water. The PCPs demonstrate an excellent fit within the CB8 cavity without structural deformation of the host. Our research methodology incorporates organic synthesis, NMR, fluorescence titration, and isothermal titration calorimetry (ITC) experiments, as well as quantum mechanical simulations, to systematically examine the binding characteristics of fluorescent mono- and dicationic PCP guests within the CB8 cavity. This study not only corroborates but also critically reevaluates certain aspects of the “high-energy water release model” for cucurbit[n]uril systems. Furthermore, the ease of modifying PCP compounds, combined with their superior water solubility compared to di- and triamantanes, and their characteristic fluorescent response in forming and disassembling host-guest complexes, elevates PCPs as promising candidates for the creation of advanced supramolecular CB8-functional materials and sensing assays.

Copper (Cu) nanoparticles (NPs) loaded on titanium(IV) oxide (TiO₂) exhibit an extinction at about λ=580 nm because of surface plasmon resonance (SPR); however, they rapidly lose their its SPR when exposed to air. In order to stabilize the Cu NPs, a multi-step photodeposition method was used to introduce chromium, which resulted in successful synthesis of a Cr₂O₃/Cu/TiO₂ sample that exhibited extinction even when exposed to air. Transmission electron microscopy, scanning transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy were utilized to analyze the Cu/TiO₂ and Cr₂O₃/Cu/TiO₂ samples with a focus on SPR of the nanoparticles and state of the Cu species. The prepared Cr₂O₃/Cu/TiO₂ samples acted as plasmonic photocatalysts in oxidation of 2-propanol under aerated conditions and visible light irradiation. Expandability of the Cr₂O₃/Cu/TiO₂ plasmonic photocatalyst was also investigated, and the results suggested the potential of a Cu-based plasmonic photocatalyst working under irradiation of visible light.

The solventless synthesis of peptides from unactivated amino acids was optimized in a twin-screw extruder (TSE). The general method enabled the preparation of dipeptides and tripeptides with no epimerization. This flow mechanochemistry approach was applied to the synthesis of aspartame, a synthetic dipeptide, prepared in a continuous mode on large scale and with high productivity.

Atomic carbon, a zerovalent atom with four non-bonded electrons, has potential utility in organic synthesis as platforms for the formation of four new covalent bonds at the carbon center. Single-carbon atom doping (SCAD) is the process of inserting an atomic carbon into a reactant molecule with no loss of atoms in the reactant. In this Concept, we overview SCAD reactions, which can be classified by physical or chemical methods.

Tris(trifluoromethyl)copper(III), Cu(CF₃)₃, was prepared for the first time and fully characterized in the form of weakly coordinated highly reactive solvent neutral adducts (DMF)₂Cu(CF₃)₃ and (MeCN)Cu(CF₃)₃. Free Cu(CF₃)₃ is an elusive molecule of distorted T-shaped geometry with Lewis acid properties, which is stabilized by solvation. Substitution of solvent molecules with monoanionic ligands in mild conditions afforded the first Cu(III)(CF₃)₃ carboxylates [Cu(CF₃)₃(OAc)]⁻ and [Cu(CF₃)₃(OBz)]⁻ and Cu(III) nitrito complex [Cu(CF₃)₃(ONO)]⁻. An improved synthesis of valuable Grushin's trifluoromethylation reagents via the intermediacy of (MeCN)Cu(CF₃)₃ was developed. (DMF)₂Cu(CF₃)₃ demonstrated promising properties in photoinduced radical C-H trifluoromethylation. Oxidation state theoretical studies showed the Cu(CF₃)₃ compounds to be borderline between classical Cu(III) and inverted ligand field Cu(I) assignment.

Hydrophilic or hydrophobic nature of the mesoporous silicate support of immobilized tungstate complex catalysts affects the selectivity of the alkene oxygenation products. In their Research Article, S. Hikichi and co-workers report that the tungstate immobilized onto a hydrophilic support, which retains silanol groups, catalyzes the epoxidation in a less polar solvent. The tungstate immobilized onto a hydrophobic support, modified with trimethylsilyl groups for capping the silanol, produces trans-diol through epoxidation and following hydration in an aqueous solvent by the highly Lewis acidic tungsten.