Activity of copper–cerium–zirconium catalysts in oxidation of hydrogen

We have studied the catalytic properties in oxidation of hydrogen for copper–cerium oxide systems deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300–1000 °C. We have shown that the catalytic activity of the samples obtained depends on the specific surface area of the original supports and the amount of reduced copper within the composition of the catalyst. In samples whose support has high specific surface area, the content of reduced metallic copper is greater and the catalytic activity is higher.     

Stabilizing DNAzymes through Encapsulation in a Metal–Organic Framework

DNAzymes are a promising class of bioinspired catalyst; however, their structural instability limits their potential. Herein, a method to stabilize DNAzymes by encapsulating them in a metal–organic framework (MOF) host is reported. This biomimetic mineralization process makes DNAzymes active under a wider range of conditions. The concept is demonstrated by encapsulating hemin-G-quadruplex (Hemin-G4) into zeolitic imidazolate framework-90 (ZIF-90), which indeed increases the DNAzyme's structural stability. The stabilized DNAzymes show activities in the presence of Exonuclease I, organic solvents, or high temperature. Owing to its elevated stability and heterogeneous nature, it is possible to perform catalysis under continuous-flow conditions, and the DNAzyme can be reactivated in situ by introducing K⁺. Moreover, it is found that the encapsulated DNAzyme maintains its high enantiomer selectivity, demonstrated by the sulfoxidation of thioanisole to (S)-methyl phenyl sulfoxide. This concept of stabilizing DNAzymes expands their potential application in chemical industry.     

Outlier Detection in QSAR Modeling of the Biological Activity of Chemicals by Analyzing the Structure–Activity–Similarity Maps

Moscow University Chemistry Bulletin - A new method for the detection of outliers in training sets used in QSAR model construction is developed. The method is based on the analysis of...     

Mechanism of the Antioxidant Activity and Structure–Activity Relationship of N-Monosubstituted Amino Acid Derivatives of Fullerene С60

Kinetics and Catalysis - The kinetic characteristics, mechanisms of activity, and relationship between the antioxidant activity and the molecular and supramolecular structure of fullerene C60 and...     

Antifungal Activity of Compounds Isolated from the Aerial Parts of Desmodium multiflorum and Their Structure–Activity Relationship

Chemistry of Natural Compounds -     

Control of Vicinal Stereocenters through Nickel-Catalyzed Alkyl–Alkyl Cross-Coupling

Vicinal stereocenters are found in many natural and unnatural compounds. Although metal-catalyzed cross-coupling reactions of unactivated alkyl electrophiles are emerging as a powerful tool in organic synthesis, there have been virtually no reports of processes that generate, much less control, vicinal stereocenters. In this investigation, we establish that a chiral nickel catalyst can mediate doubly stereoconvergent alkyl–alkyl cross-coupling, specifically, reactions of a racemic pyrrolidine-derived nucleophile with cyclic alkyl halides (as mixtures of stereoisomers) to produce vicinal stereocenters with very good stereoselectivity.     

Ring-Opening Lithiation–Borylation of 2-Trifluoromethyl Oxirane: A Route to Versatile Tertiary Trifluoromethyl Boronic Esters

Stereogenic trifluoromethyl-substituted carbon centers are highly sought-after moieties in pharmaceutical and agrochemical discovery. Here, we show that lithiation–borylation reactions of 2-trifluoromethyl oxirane give densely functionalized and highly versatile trifluoromethyl-substituted α-tertiary boronic esters. The intermediate boronate complexes undergo the desired 1,2-rearrangement of the carbon-based group with complete retentive stereospecificity, a process that was only observed in non-polar solvents in the presence of TESOTf. Although the trifluoromethyl group adversely affects subsequent transformations of the α-boryl group, Zweifel olefinations provide trifluoromethyl-bearing quaternary stereocenters substituted with alkenes, alkynes and ketones.     

Linker Hydrophilicity Modulates the Anticancer Activity of RGD–Cryptophycin Conjugates

Most anticancer agents are hydrophobic and can easily penetrate the tumor cell membrane by passive diffusion. This may impede the development of highly effective and tumor-selective treatment options. A hydrophilic β-glucuronidase-cleavable linker was used to connect the highly potent antimitotic agent cryptophycin-55 glycinate with the α_vβ₃ integrin ligand c(RGDfK). Incorporation of the self-immolative linker containing glucuronic acid results in lower cytotoxicity than that of the free payload, suggesting that hydrophilic sugar linkers can preclude passive cellular uptake. In vitro drug-release studies and cytotoxicity assays demonstrated the potential of this small molecule–drug conjugate, providing guidance for the development of therapeutics containing hydrophobic anticancer drugs.     

Synthesis and Antitumor Activity of C-2／C-10 Modified Analogues of Docetaxel

Four 10-propionyl docetaxel analogues (lla-d) with 2α-amido substituents were prepared, and their antitumor activity against three solid tumor cell lines and their drug-resistant counterparts were determined.     

Tunable Anticancer Activity of Furoylthiourea-Based RuII–Arene Complexes and Their Mechanism of Action

Fourteen new Ru^II–arene (p-cymene/benzene) complexes ( C1 – C14 ) have been synthesized by varying the N-terminal substituent in the furoylthiourea ligand and satisfactorily characterized by using analytical and spectroscopic techniques. Electrostatic potential maps predicted that the electronic effect of the substituents was mostly localized, with some influence seen on the labile chloride ligands. The structure–activity relationships of the Ru–p-cymene and Ru–benzene complexes showed opposite trends. All the complexes were found to be highly toxic towards IMR-32 cancer cells, with C5 (Ru–p-cymene complex containing C₆H₂(CH₃)₃ as N-terminal substituent) and C13 (Ru–benzene complex containing C₆H₄(CF₃) as N-terminal substituent) showing the highest activity among each set of complexes, and hence they were chosen for further study. These complexes showed different behavior in aqueous solutions, and were also found to catalytically oxidize glutathione. They also promoted cell death by apoptosis and cell cycle arrest. Furthermore, the complexes showed good binding ability with the receptors Pim-1 kinase and vascular endothelial growth factor receptor 2, commonly overexpressed in cancer cells.     

Efficient Continuous-Flow Synthesis and Evaluation of Anticancer Activity of Novel Quinoline–Pyrazoline Derivatives

Russian Journal of Organic Chemistry - An efficient and simple continuous-flow synthetic protocol for novel quinoline-tethered pyrazoline derivatives, which involves condensation of...     

Structural Basis for Carbapenemase Activity of the OXA-23 β-Lactamase from Acinetobacter baumannii

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Effect of the Acid–Base Properties of the Support on the Activity of Pd–Zeolite Catalysts for CO Oxidation

The effect of the acid–base properties of zeolite Y on the activity of palladium–zeolite catalysts for CO oxidation was studied. The modification of the support with basic additives was found to improve the catalyst activity. A linear correlation between the ratio between the amounts of O₂and CO adsorbed on the surface of palladium and the catalyst activity was established.     

Temperature Control of Sequential Nucleation–Growth Mechanisms in Hierarchical Supramolecular Polymers

Upon cooling in solution, chiral triarylamine tris-amide unimers produce organogels by stacking into helical supramolecular polymers, which subsequently bundle into larger fibers. Interestingly, circular dichroism, vibrational circular dichroism, and AFM imaging of the chiral self-assemblies revealed that monocolumnar P-helical fibrils formed upon fast cooling, whereas bundled M-superhelical fibers formed upon slow cooling. The mechanistic study of this structural bifurcation reveals the presence of a strong memory effect, reminiscent of a complex stepwise combination of primary and secondary nucleation-growth processes. These results highlight the instrumental role of sequential self-assembly processes to control supramolecular architectures of multiple hierarchical order.     

Microwave-Assisted Synthesis and Antimicrobial Activity of Novel Pyrazole–Indanone Hybrid Analogs

Russian Journal of Organic Chemistry - A simple and efficient microwave-assisted protocol has been developed for the synthetic of a series of novel pyrazole–indanone hybrid analogs. The...     

Activity Essential Residue Analysis of Taxoid 10β-O-Acetyl Transferase for Enzymatic Synthesis of Baccatin

Taxoid 10β-O-acetyl transferase (DBAT) is a key enzyme in the biosynthesis of the famous anticancer drug paclitaxel, which catalyses the formation of baccatin III from 10-deacetylbaccatin III (10-DAB). However, the activity essential residues of the enzyme are still unknown, and the acylation mechanism from its natural substrate 10-deacetylbaccatin III and acetyl CoA to baccatin III remains unclear. In this study, the homology modelling, molecular docking, site-directed mutagenesis, and kinetic parameter determination of the enzyme were carried out. The results showed that the enzyme mutant DBAT^H162A resulted in complete loss of enzymatic activity, suggesting that the residue histidine at 162 was essential to DBAT activity. Residues D166 and R363 which were located in the pocket of the enzyme by homology modelling and molecular docking were also important for DBAT activity through the site-directed mutations. Furthermore, four amino acid residues including S31 and D34 from motif SXXD, D372 and G376 from motif DFGWG also played important roles on acylation. This was the first report of the elucidation of the activity essential residues of DBAT, making it possible for the further structural-based re-design of the enzyme for efficient biotransformation of baccatin III and paclitaxel.     

Synthesis and Structure–Antitumor Activity Relationship of Sulfonyl 5-Fluorouracil Derivatives

Novel sulfonyl 5-fluorouracil derivatives 2 (5-fluoro-1-(arylsulfonyl)pyrimidine-2,4(1H,3H)-diones) have been synthesized via the reaction of 5-fluorouracil with sulfonyl chloride. Their chemical structures were confirmed by means of ¹H NMR, ¹³C NMR, IR, mass spectra, and elemental analyses, and, in the case of 2a, its structure was established by single crystal X-ray diffraction. Some of the compounds were assayed for anticancer (HL-60 and BEL-7402 cells) activities. Structure–activity relationship (SAR) analysis discovered that the anticancer activity was related to the configuration, and that electron-withdrawing groups at 2-position or 4-position on the aryl group of arylsulfonyl derivatives of 5-fluorouracil could enhance the anticancer activity against the BEL-7402 cells.

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