Russian Chemical Bulletin最新文献

Convenient syntheses of functionalized PCHNH-containing amines have been developed based on the nucleophilic addition of trivalent phosphorus acid esters to various imines. Subsequent acylation of these amines at the NH fragment opens the way to promising types of amides and sulfonamides of functionalized aminomethyl-substituted organophosphorus acids. The resulting compounds contain polar amide (sulfonylamide) and phosphoryl moieties, have potential biological activity, and are also of interest as effective extractants and polydentate chelating ligands.

The synthesis of a mixture of polyprenyl monoesters of 1,2,4,5-benzenetetracarboxylic (pyromellitic) acid, potential inhibitors of pathogenic viruses replication, was described for the first time. A more efficient protocol for obtaining a mixture of (±)-2,3-dihydropoly-prenylpyromellitates was proposed compared to the previously described one.

Two accesses to N-Boc-(S)-prolinonitrile (tert-butyl (S)-2-cyanopyrrolidine-1-carboxylate) from (S)-l-proline, namely, a three-step procedure that involves synthesis of intermediate N-Boc-l-Pro-NH₂ and a six-step procedure that excludes the synthesis of this intermediate, were compared. The second approach despite more steps is easier to accomplish and provides the target compound in 47% yield based on the starting l-proline.

A new mechanism of singlet-triplet conversion of electron pairs of diamagnetic substrates in the active sites of enzymes is proposed to explain the effect of nuclear spins and strong magnetic fields on the enzymatic synthesis of adenosine triphosphate (ATP) in vitro and in vivo. It is shown that the Fermi contact interaction, inducing a redistribution of electron density in enzyme-substrate complexes ²⁵Mg-ADP—ATPase, enables a decrease of the negative charge on the terminal groups of ADP. Thus, the nuclear spin of the ²⁵Mg isotope decreases the Coulomb repulsion of the negatively charged fragments of the substrates and increases the rate of the enzymatic formation of ATP. The theoretical results explain the experimentally observed effect of the nuclear spin of the ²⁵Mg isotope on the intracellular synthesis of ATP in Escherichia coli bacteria in strong magnetic fields.

Analysis of absorption and fluorescence spectra at 293 and 77 K, as well as fluorescence excitation spectra of bis(aza-18-crown-6)-containing dibenzylidenecyclohexanone (CD6) and its complexes confirms the presence of photorecoordination in CD6•(Mⁿ⁺)₂ (M = Ba²⁺, Sr²⁺, Ca²⁺, K⁺). The process is completely blocked in low-temperature butyronitrile glass. Coordination of the metal cation to the carbonyl group of the CD6 molecule is accompanied by fluorescence enhancement, while coordination of the cations to the aza-18-crown-6 ether residues, on the contrary, leads to its quenching. In the case of the complexes CD6•(Mⁿ⁺)₂, correlations were observed between the stability constants, the values of the blue shifts in the absorption spectra, the red shifts in the fluorescence spectra, and the diameters of the cations. The CD6 dienone forms complexes with the compositions CD6•Mⁿ⁺, CD6•(Mⁿ⁺)₂, and Mⁿ⁺•CD6•(Mⁿ⁺)₂ with the cations Mg²⁺, Li⁺, and Na⁺. A correlation of the above-mentioned parameters with the cation surface charge density was observed for the complexes Mⁿ⁺•CD6•(Mⁿ⁺)₂. The possibility of influencing the efficiency of complexation and the degree of photorecoordination by varying the nature of the central acceptor fragment in the dye series CD4, CD5, CD6 (CD4 and CD5 are dyes similar to CD6 with central cyclobutanone (CD4) and cyclopentanone (CD5) fragments, respectively) was determined.

Along with 4-acetoxybenzoic acid (4-ABA) and O-acetylvanillic acid (AVA), the syringic acid derivative O-acetylsyringic acid (ASA) can be used as an AB-type comonomer in polycondensation reactions. All three monomers have comparable polycondensation rates, and therefore the copolycondensation of 4-ABA, ASA, and AVA in the melt is expected to yield copolyesters with a random or nearly random macromolecular structure. From a mixture of ASA, 4-ABA, and 4′-acetoxybiphenyl-4-carboxylic acid (4-ABCA), a ternary thermotropic copolyester with a “liquid crystal glass” structure was synthesized. This copolyester has a lower softening temperature and a higher glass transition temperature compared to similar ternary copolyesters based on 4-ABA and 4-ABCA.

A new one-step method for the synthesis of the PtCo/ZSM-5 catalysts for CO oxidation was proposed. Heteronuclear acetate complexes of the empirical composition PtCo_x(AcO)_y containing Pt^II and Pt^IV in ratios with Co of 1: 1 or 1: 2 were used as precursors. According to the data of scanning and transmission electron microscopy and XPS, the impregnation of the HZSM-5 zeolite (Si/Al = 28) with a solution of the complexes in glacial acetic acid followed by decomposition at 200 or 300 °C leads to the stabilization of highly dispersed partially reduced Pt^δ+ particles interacting with cobalt ions on the zeolite surface. Their joint action and a possibility of formation of new Pt—O_x—Co sites active in the preferential oxidation of CO ensure high efficiency and selectivity of the process in an H₂ excess. At the relatively low Pt content from 0.1 to 0.3 wt.%, the complete conversion of CO on these catalysts is achieved in the wide temperature range from 50 to 130 °C.

The review is devoted to chemical modifications and properties of aminopurines, particularly 2(6)-mono- and 2,6-diaminopurines, the introduction of a glycoside moiety into the aminopurine system, and applications of aminopurines.

A series of substituted N-phenoxyacetyltaurates was synthesized from the corresponding phenoxyacetates by the reaction with potassium taurate. The unusual solid-state structure was established for potassium salt of N-(4-chlorophenoxyacetyl)taurine. According to the X-ray diffraction data, it consists of three symmetry-independent layers. Apart from ionic interactions and hydrogen bonds, the layers are stabilized by weak C—H⋯Cl van der Waals interactions. N-Substituted potassium taurates effectively reduced the level of lipopolysaccharide-induced proinflammatory cytokines in Raw264,7 cells. N-(3-Methoxyphenoxyacetyl)taurine inhibited a broad spectrum of key inflammatory mediators. The evaluation of biosafety demonstrated the absence of cytotoxicity of the compounds under study.