Regio- and stereocontrolled synthesis and conformational analysis of benzimidazole nucleosides

Regio- and stereocontrolled synthesis and conformational analysis of a series of benzimidazole nucleosides were achieved. A simple method by ¹H NMR 1D NOE experiment was developed for estimation of syn or anti conformation of benzimidazole nucleosides. Substituents at C2 of benzimidazole demonstrated to play a key role both in the unexpected regioselectivity of the glycosidic reaction and in the conformation distributions of the final products.     

Arylesters of alkylsulfonic acids in sediments Part III of organic compounds as contaminants of the Elbe River and its tributaries

Sediments from the Elbe River and from its major tributaries are shown to be contaminated with arylesters of alkylsulfonic acids. Here we report on the structure elucidation and quantification of aryl esters of alkylsulfonic acids. Chromatographic separation and mass spectrometric properties are discussed. Congener-specific analyses revealed a highly similar pattern throughout the area investigated. Alkylsulfonic acid phenylesters were present at almost all sampling locations. Amounts ranged from 33 000 μg/kg near the industrial region of Bitterfeld to 15 μg/kg in wadden sea sediments. Concentrations of alkylsulfonic acid cresylesters were between 10–40% of the phenylesters, and fell below the detection limit only in the Elbe estuary. The presence of aryl esters of alkylsulfonic acids in all sediment samples analyzed indicates a widespread distribution of these compounds in the environment. Previous literature described these compounds erroneously as phenoxyalkanes. Received: 5 August 1997 / Accepted: 21 August 1997     

Theoretical studies on the reaction path and dynamics of the reaction CH_3+H_2O→CH_4+OH

The reaction path, the dynamical properties along the reaction path and CVT rate constants are computed by the ab initio MO method, the reaction path Hamiltonian theory and the variational transition state theory. The results show that the effect of the electron correlation energy on activation barrier is large, the recrossing and tunneling effects exist in the reaction.     

Vegetable tanning substances. Dependence of the tanning properties of extracts on their composition

Information is given on vegetable tanning substances, their classification, distribution in the plant world, and structure, and the dependence of their tanning properties on their composition, and also on methods of enriching tanning extracts. The review of literature sources includes publications from 1950 to 1989.A. S. Sadykov Institute of Bioorganic Chemistry, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 293–307, May–June, 1990.     

The roots ofDictamnus angustifolius

Summary From the roots ofDictamnus angustifolius G. Don. collected in Chimgan at the end-of-fruit-bearing stage have been isolated alkaloids dictamnine, skimmianine, -fagarine, isodictamnine, isopteleine, and preskimmianine, the limonoid fraxinellone, and the steroid -sitosterol. This is the first time that any of these substances, with the exception of dictamnine and skimmianine, have been found in this plant.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 476–478, July–August, 1978.     

The theory of dispersion of chemically active solutes in a rectilinear flow field: The vector problem

In this paper and its sequel we seek an understanding of diffusion and reaction processes in multicomponent systems under convective conditions. To do this, we construct dispersion approximations to c, the solution of the vector convective diffusion equation, and to its transverse average, . Dispersion coefficients are not the direct route to dispersion approximations in the vector problem. Yet constant long time dispersion coefficients exist and imply a rearrangement of the Hermite expansion of . We deduce the rearrangement and introduce useful approximations thereto.     

Low Pass metallic mesh interference filters for operation in the 165 GHz to 880 GHz region

Low Pass metallic mesh interference filters have been designed and constructed for operation in the region 340 m (880 GHz) to 1.8 mm (165 GHz). These filters have been shown to have excellent edge characteristics and good rejection regions. The results show that the mesh filter can be effectively used in both millimetre and submillimetre regions.Part of this work was performed while this author was at Heriot-Watt University, Edinburgh, U.K.