Synthesis of a key precursor for orienticin C and model study on ruthenium-mediated macrocyclization

A tripeptido--arene--ruthenium complex was prepared as a key precursor for the projected synthesis of orienticin C, demonstrating that the cyclopentadienylruthenium moiety can be attached to a chloroarene in the presence of multiple functionality. The ruthenium-mediated intramolecular SNAr reaction for formation of the required diaryl ether linkage was successfully tested on a model system.     

Bisphosphonate derivatives of nucleoside antimetabolites: hydrolytic stability and hydroxyapatite adsorption of 5'-beta,gamma-methylene and 5'-beta,gamma-(1-hydroxyethylidene) triphosphates of 5-fluorouridine and ara-cytidine

Kinetics of the hydrolytic reactions of four bisphosphonate derivatives of nucleoside antimetabolites, viz., 5-fluorouridine 5'-beta,gamma-(1-hydroxyethylidene) triphosphate ( 4), 5-fluorouridine 5'-beta,gamma-methylene triphosphate ( 5), ara-cytidine 5'-beta,gamma-(1-hydroxyethylidene) triphosphate ( 6), and ara-cytidine 5'-beta,gamma-methylene triphosphate ( 7), have been studied over a wide pH range (pH 1.0-8.5) at 90 degrees C. With each compound, the disappearance of the starting material was accompanied by formation of the corresponding nucleoside 5'-monophosphate, the reaction being up to 2 orders of magnitude faster with the beta,gamma-(1-hydroxyethylidene) derivatives ( 4, 6) than with their beta,gamma-methylene counterparts ( 5, 7). With compound 7, deamination of the cytosine base competed with the phosphate hydrolysis at pH 3-6. The measurements at 37 degrees C (pH 7.4) in the absence and presence of divalent alkaline earth metal ions (Mg (2+) and Ca (2+)) showed no sign of metal ion catalysis. Under these conditions, the initial product, nucleoside 5'-monophosphate, underwent rapid dephosphorylation to the corresponding nucleoside. Hydrolysis of the beta,gamma-methylene derivatives ( 5, 7) to the corresponding nucleoside 5'-monophosphates was markedly faster in mouse serum than in aqueous buffer (pH 7.4), the rate-acceleration being 5600- and 3150-fold with 5 and 7, respectively. In human serum, the accelerations were 800- and 450-fold compared to buffer. In striking contrast, the beta,gamma-(1-hydroxyethylidene) derivatives did not experience a similar decrease in hydrolytic stability. The stability in human serum was comparable to that in aqueous buffer (tau 1/2 = 17 and 33 h with 4 and 6, respectively), and on going to mouse serum, a 2- to 4-fold acceleration was observed. To elucidate the mineral-binding properties of 4- 7, their retention on a hydroxyapatite column was studied and compared to that of zoledronate ( 1a) and nucleoside mono-, di-, and triphosphates.     

Back Cover: Bio-Inspired Bimetallic Cooperativity Through a Hydrogen Bonding Spacer in CO2 Reduction (Angew. Chem. Int. Ed. 8/2023)

At the core of carbon monoxide dehydrogenase (CODH) active site two metal ions together with hydrogen bonding scheme from amino acids orchestrate the interconversion between CO₂ and CO. We have designed a molecular catalyst implementing a bimetallic iron complex with an embarked second coordination sphere with multi-point hydrogen-bonding interactions. We found that, when immobilized on carbon paper electrode, the dinuclear catalyst enhances up to four fold the heterogeneous CO₂ reduction to CO in water with an improved selectivity and stability compared to the mononuclear analogue. Interestingly, quasi-identical catalytic performances are obtained when one of the two iron centers was replaced by a redox inactive Zn metal, questioning the cooperative action of the two metals. Snapshots of X-ray structures indicate that the two metalloporphyrin units tethered by a urea group is a good compromise between rigidity and flexibility to accommodate CO₂ capture, activation, and reduction.     

The utility of ultra-performance liquid chromatography/electrospray ionisation time-of-flight mass spectrometry for multi-residue determination of pesticides in strawberry

The utility of ultra-performance liquid chromatography/orthogonal-acceleration time-of flight mass spectrometry (UPLC/TOFMS) for the rapid qualitative and quantitative analysis of 100 pesticides targeted in strawberry was assessed by comparing results with those obtained using a validated in-house UPLC tandem mass spectrometry (MS/MS) multi-residue method. Crude extracts from retail strawberry samples received as part of the 2007 annual UK pesticide residues in food surveillance programme were screened for the presence of pesticide residues using UPLC/TOFMS. Accurate mass measurement of positive and negative ions allowed their extraction following 'full mass range data acquisition' with negligible interference from background or co-eluting species observed during UPLC gradient separation (in a cycle time of just 6.5 min per run). Extracted ion data was used to construct calibration curves and to detect and identify any incurred residues (i.e. pesticides incorporated in or on the test material following application during cultivation, harvest and storage). Calibration using matrix-matched standards was performed over a narrow concentration range of 0.005-0.04 mg kg(-1) with determination coefficients (r2) > or =0.99 for all analytes with the exception of malathion/fenarimol/fludioxanil (r2 = 0.98), quassia/pymetrazine (r2 = 0.97) and fenthion sulfone (r2 = 0.95). Residues found in selected samples ranged from 0.025-0.28 mg kg(-1) and were in excellent agreement with results obtained using UPLC/MS/MS. Mass measurement accuracies of < or =5 ppm were achieved consistently throughout the separation, mass range and concentration range of interest thus providing the opportunity to obtain discrete elemental compositions of target ions.     

A 2D coordination polymer with canted ferromagnetism constructed from ferromagnetic [Ni(II)Co(II)] nodes

A bimetallic coordination polymer, infinity (2)[{LNi (II)Co (II)}(dca) 2], has been constructed from heterobinuclear [Ni (II)Co (II)] nodes and dicyanamido spacers [L (2-) is the dianion of the Schiff base resulting from the 2:1 condensation of 3-methoxysalicyladehyde with 1,3-propanediamine; L (2-) = N, N'-propylenebis(3-methoxysalycilideneiminato)]. The intranode Co (II)-Ni (II) interaction was found to be ferromagnetic because of the orthogonality of the magnetic orbitals. Below 12 K, the onset of the canted ferromagnetic ordering is observed.     

Ruthenium-Catalyzed Direct Reductive Amination of Carbonyl Compounds for the Synthesis of Amines: An Overview

Reductive amination is a valuable method for amine synthesis that has been the topic of a century‘s worth of in-depth study in both academia and industry. Amines and their derivatives serve as incredibly adaptable building blocks for a broad array of organic substrates and are significant precursors for a myriad of advanced chemicals, physiologically active compounds, agrochemicals, biomolecules, pharmaceuticals, and polymers. The creation of innovative catalytic processes for the long-term and selective synthesis of amines from readily accessible and environmentally benign reagents remains a top priority in chemical research. Both heterogeneous and homogeneous catalysts have been designed with success to enable these reactions to explore new amines. Ruthenium catalysts are employed in reductive amination owing to their stability, selectivity, versatility, low toxicity, and high efficiency. This review comprehensively overviews the Ru-catalyzed reductive amination processes and includes the literature from 2009 to 2022.     

Dual Chromophoric Meso-Aryl BODIPYs with Aggregation Induced Red-Emission Characteristics: Optical Properties and their Application in Fe3+ Detection

Herein, we report the design of meso-aryl BODIPYs as a structural motif for aggregation-caused quenching (ACQ) to aggregation-induced emission (AIE) transformation. A series of meso-aryl BODIPY derivatives were synthesized, by systematically increasing the size of the chromophore at the meso-position from phenyl to pyrene. The effect of various factors, such as the aryl ring size, solvents, viscosity, and metal cations, on the photophysical properties was analyzed. The emission properties are well correlated with the flexibility of the aromatic ring for free rotation around the C_aryl−C_BODIPY bond. Accordingly, meso-phenanthrene BODIPY ( PhB ) has the highest emission characteristics. The emission property of less bulky aryl-substituted BODIPYs increases by increasing the solvent viscosity. The interaction of Fe³⁺ ions with aryl-BODIPYs provides a prominent photophysical response based on Lewis-acid supported decomplexation of BF₂ in aryl-BODIPYs. The bichromophoric meso-aryl BODIPYs exhibit notable intramolecular excitation energy transfer from the aromatic ring to the BODIPY core, which is higher in meso-anthracene BODIPY( AB ). Hence, decorating BODIPYs with polycyclic aromatic systems generates a twisted structure, which inhibits the π-π stacking between the planar aromatic molecules. This can be proposed as an effective approach at the molecular level to convert planar aryl luminophores having ACQ to AIEgens. Besides, the meso-pyrene BODIPY derivative shows excellent mechanofluorochromic behaviour.     

Equilibrium Diffusion on the Cone of Discrete Radon Measures

Let \({\mathbb {K}(\mathbb {R}^{d})}\) denote the cone of discrete Radon measures on \(\mathbb {R}^{d}\). There is a natural differentiation on \(\mathbb {K}(\mathbb {R}^{d})\): for a differentiable function \(F:\mathbb {K}(\mathbb {R}^{d})\to \mathbb {R}\), one defines its gradient \(\nabla ^{\mathbb {K}}F\) as a vector field which assigns to each \(\eta \in \mathbb {K}(\mathbb {R}^{d})\) an element of a tangent space \(T_{\eta }(\mathbb {K}(\mathbb {R}^{d}))\) to \(\mathbb {K}(\mathbb {R}^{d})\) at point η. Let \(\phi :\mathbb {R}^{d}\times \mathbb {R}^{d}\to \mathbb {R}\) be a potential of pair interaction, and let μ be a corresponding Gibbs perturbation of (the distribution of) a completely random measure on \(\mathbb {R}^{d}\). In particular, μ is a probability measure on \(\mathbb {K}(\mathbb {R}^{d})\) such that the set of atoms of a discrete measure \(\eta \in \mathbb {K}(\mathbb {R}^{d})\) is μ-a.s. dense in \(\mathbb {R}^{d}\). We consider the corresponding Dirichlet form

$$\mathcal{E}^{\mathbb{K}}(F,G)={\int}_{\mathbb K(\mathbb{R}^{d})}\langle\nabla^{\mathbb{K}} F(\eta), \nabla^{\mathbb{K}} G(\eta)\rangle_{T_{\eta}(\mathbb{K})}\,d\mu(\eta). $$

Integrating by parts with respect to the measure μ, we explicitly find the generator of this Dirichlet form. By using the theory of Dirichlet forms, we prove the main result of the paper: If d ≥ 2, there exists a conservative diffusion process on \(\mathbb {K}(\mathbb {R}^{d})\) which is properly associated with the Dirichlet form \(\mathcal {E}^{\mathbb {K}}\).

     

Polydopamine‐Mediated Immobilization of Alginate Lyase to Prevent P. aeruginosa Adhesion

Given alginate's contribution to Pseudomonas aeruginosa virulence, it has long been considered a promising target for interventional therapies, which have been performed by using the enzyme alginate lyase. In this work, instead of treating pre‐established mucoid biofilms, alginate lyase is immobilized onto a surface as a preventive measure against P. aeruginosa adhesion. A polydopamine dip‐coating strategy is employed for functionalization of polycarbonate surfaces. Enzyme immobilization is confirmed by surface characterization. Surfaces functionalized with alginate lyase exhibit anti‐adhesive properties, inhibiting the attachment of the mucoid strain. Moreover, surfaces modified with this enzyme also inhibit the adhesion of the tested non‐mucoid strain. Unexpectedly, treatment with heat‐inactivated enzyme also inhibits the attachment of mucoid and non‐mucoid P. aeruginosa strains. These findings suggest that the antibacterial performance of alginate lyase functional coatings is catalysis‐independent, highlighting the importance of further studies to better understand its mechanism of action against P. aeruginosa strains.