Lead,cadmium, and arsenic in commercial algae of the Sea of Japan

The concentrations of toxic elements (arsenic, cadmium, lead) in commercial algae Saccharina japonica and Ahnfeltia tobuchiensis from different habitats of the Sea of Japan have been determined. Bioaccumulation of heavy metals has been analyzed with respect to the habitat and growth conditions. The lead content of Sascharina japonica from all habitats and arsenic content of the same alga species from the Ol’ga Bay, Kievka Bay, and Tatar Strait have been found to exceed maximum permissible levels. Increased lead concentrations have been detected in Ahnfeltia tobuchiensis. Samples of Ahnfeltia tobuchiensis collected from the bottom layer contain more toxic elements than those from the upper layer.     

Acylation of 1-methoxy-3-methyl-1-triazene 2-oxide

Chlorides and anhydrides of carboxylic (including dicarboxylic) acids react with salts of 1-methoxy-3-methyl-1-triazene 2-oxides to give the corresponding 3-acyl-1-methoxy-3-methyl-1-triazene 2-oxides.     

Advances in the synthesis of 7-(3-cyclopentyloxy-4-methoxyphenyl)-hexahydro-3<Emphasis Type="Italic">H</Emphasis>-pyrrolizin-3-one (Pyrromilast)–a promising agent for treatment of chronic obstructive pulmonary disease

The review summarizes the known approaches to diastereo- and enantioselective synthesis of 7-(3-cyclopentyloxy-4-methoxyphenyl)hexahydro-3H-pyrrolizin-3-one (Pyrromilast), a highly active inhibitor of subtype 4B phosphodiesterase and a promising agent for treatment of chronic obstructive pulmonary disease.     

Acetylenic derivatives of betulonic acid amide as a new type of compounds possessing spasmolytic activity

Efficient and versatile synthetic procedures towards novel derivatives of betulonic acid via Mannich reaction, Sonogashira cross-coupling, and copper(i)-catalyzed 1,3-dipolar cyclo-additions were developed. Introduction of secondary amines (Mannich reaction) into betulonic acid amides led to derivatives possessing marked spasmolytic activity, which is not characteristic of the triterpene fragment.     

Quantum chemistry of many-electron systems: high-priority aspects

The review generalizes the studies devoted to the development of a new quantum chemistry method representing an alternative to the Hartree–Fock approximation. Based on the hypothesis of prohibition of equipotential surfaces, which clarifies the physical sense of the Pauli exclusion principle, and taking account of the condition for antisymmetrical wave function of the triplet state (3S) of He atom, the Hartree–Fock approximation is inappropriate for a priori determination of the nodal surfaces of many-electron wave functions (MWFs) for the test systems traditionally used in quantum chemistry, namely, excited triplet state of H₂ molecule and the ground electronic states of Li atom and LiH molecule. The nodal surfaces of the wave functions corresponding to the minimum basis set of Slater orbitals in the Hartree–Fock approximation are constructed and analyzed. An alternative to the Hartree–Fock approximation is provided by the MWF quantum chemical method being developed by the authors. In the MWF method, the nodal surfaces for H₂(³Σ _u ^v ) and Li(²S) are specified a priori. Some aspects of geometric interpretation of the Pauli exclusion principle are discussed. Unlike the MWF method, the Hartree–Fock approximation is unsuitable for taking account of the dependence of the MWF nodal surfaces on the nuclear charges and on correlation effects related to the motion of electrons with antiparallel spins because such nodal surfaces are predefined by the mathematical properties of Slater determinants rather than by physically clear and more practically valuable algebraic products of electrostatic potential differences.     

Calculation of possible stabilization of glycosyl carbocations in furanosides by different theoretical methods

The paper deals with the comparison of different theoretical methods for the calculation of stabilization energies of glycosyl cations from fucofuranoside glycosyl donors containing different protecting groups at atom O(3). The experimental and calculated data on stereoselectivity of glycosylation were compared. The formation of the stabilized glycosyl cations is considered as one of the possible steps of glycosylation reaction, which exerts influence on the stereoselectivity of the process and makes it possible to obtain difficultly accessible 1,2-cis-glycosides. Semi-empirical and ab initio methods without allowance for the electron correlation underestimate the stabilization energy values. The allowance for the electron correlation in the MP2 approximation, as well as the calculations by density functional theory, allowed us to obtain the data corresponding to the experimentally observed stereoselectivity.     

Quantum chemical studies of azoles 4. A novel elimination–addition mechanism of tetrazole and 1,2,4-triazole electrophilic substitution

Thermodynamic parameters of the addition–elimination and elimination–addition electrophilic substitution reactions of 1H-tetrazole and 1,2,4-1H-triazole obtained from DFT B3LYP/ 6-31G(d,p) quantum chemical calculations with proton as model electrophile are compared. According to calculations, the elimination–addition reactions can proceed without preliminary formation of N-protonated azolium salts.     

Crystal associates of 18-crown-6 and polyfluoro(het)arylenediamines: structure,properties, and selectivity of formation

The new group of objects in crystal engineering, namely, 1 : 1 associates of polyfluoro(het)arylenediamines and 18-crown-6, being supramolecular 1D assemblies, is considered. Diamine isomerism is shown to serve as a design tool for control of the supramolecular architecture, and the nature of the aromatic framework and location and volume of substituents determine linear dimensions of the elementary unit in an assembly. A linear dependence of the enthalpy of melting of co-crystals on the length of the assembly unit is observed in the series of the meta-(het)arylenediamine and 18-crown-6 associates. The effect of selective co-crystallization of polyfluoroarylenediamines with crown ether is used in practice for the isolation of high-purity compounds from mixtures of products of the non-selective amination of basic polyfluoroarenes.     

Alkylation of toluene with dichloromethane in the presence of triisobutylaluminum and perfluorophenylborates

¹H NMR method showed that in systems based on triisobutylaluminum (TIBA) and triphenylcyclopropenylium [Ph₃C₃]⁺[B(C₆F₅)₄]–(CPB) or triphenylmethylium [Ph₃C]⁺[B(C₆F₅)₄]–(TB) perfluorophenylborates in a toluene–dichloromethane mixture the Friedel–Crafts process occurs with the formation of ditolylmethane (DTM) accompanied by the complete decomposition of TIBA to form isobutane. ¹⁹F NMR spectroscopy showed that the [B(C₆F₅)₄]–anion decomposes in the systems to form B(C₆F₅)₃ and HC₆F₅. The short-living [AlBu₂ ⁱ]+ cation formed in the reaction of perfluorophenylborates with TIBA is assumed to be the species initiating the process. It has been shown that CPB is less reactive than TB. The addition of a stoichiometric amount of Ph₂CCpFluHfMe₂ exerts no effect on the process with the CPB-containing system but inhibits the reaction in the case of TB.