JSCS Vol 65, No. 8
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The crystal structure of
14-oxo-13,14-seco-5a-cholest-13(18)-en-3b-yl acetate and the assignment of the
configuration of its acetoxy derivatives
MIRA S. BJELAKOVIC*, VLADIMIR D. PAVLOVIC*,**, LJUBINKA LORENC*,**, BERNARD TINANT*** and JEAN-PAUL DECLERCQ***
*Center for Chemistry, ICTM, P.O.
Box 815, YU-11001 Belgrade,
**Faculty of Chemistry, University of Belgrade, Studentski trg 16, P.O. Box 158, YU-11001 Belgrade, Yugoslavia and
***Laboratoire de Chemie Physique et de Cristallographie, Universite Catholoque de louvain, 1 Place Lous Pasteur, B-1348 Louvain-la Neuve, Belgium
(Received 15 March 2000)
The crystal structure of 14-oxo-13, 14-seco-5a-cholest-13(18)-en-3b-yl acetate (2), obtained (in addition to the (E)- D12-isomer 3) by oxidative fragmentation of the C(13)-C(14) bond of 14a-hydroxy-5a-cholestten-3b-yl acetate (1), was determined by X-ray analysis. In addition, the configurations of the acetoxy derivatives 4-6, formed by the thermal lead tetraacetate oxidation of 1, were deduced from the relevant 1H-NMR parameters.
Keywords: X-ray analysis, 14-oxo, 13, 14-seco-5a-cholest-13(18)-en-3b-yl acetate, acetoxy derivatives of, 1H-NMR.
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Valine-mediated borane reduction of ketones
A. V. TEODOROVIC, M. D. JOKSOVIC, S. K. KONSTANTINOVIC, J. N. MILOVANOVIC and B. M. MOJSILOVIC
Faculty of Science, University of Kragujevac, P.O. Box 60, YU-34000 Kragujevac, Yugoslavia
(Received 24 November
Acetophenone, 3,3-dimethyl-2-butanone, 3-methyl-2-butanone, and 2-pentanone were reduced with (S)-valine-mediated borane in very good yields (86-91 %) giving predominantly alcohols of the (R)-configuration (80, 64, 55 and 36 % ee, respectively).
Keywords: valine-mediated borane, chiral reduction, acetophenone.
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Isolation and antimicrobial acitivity of anthraquinones from some species of the lichen genus Xanthoria
N. T. MANOJLOVIC, S. SOLUJIC, S. SUKDOLAK and LJ. KRSTIC*
Faculty of Science, University of
Kragujevac, P.O. Box 60, YU-34000 Kragujevac and
*Center for Chemistry, ICTM, P.O. Box 815, YU-11001 Belgrade, Yugoslavia
(Received 20 December
1999, revised 3 May 2000)
The isolation of six anthraquinones, erythroglaucin, physcion, xanthorin, emodin, fallacinal and teloschistin, from three species of the lichen genus Xanthoria (X. fallax, X. elegans and X. policarpa) is reported. Physcion is the dominant anthraquinone in all species. the anthraquinones showed broad-spectrum antifingal activity and selective activity against some phytopathogenic bacterial species.
Keywords: anthraquinones, Xanthoria, antibacterial activity, antifungal activity.
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The vanadium isotopic constitution of petroleum asphaltenes: La Luna Formation (Venezuela)
PAVLE I. PREMOVIC*, DRAGAN M. DJORDJEVIC*, IVANA R. TONSA*, LILIANA LOPEZ**, SALVADOR LOMANOCO**, MIRJANA S. PAVLOVIC***, MIOMIR V. VELJKOVIC*** and OLIVERA M. NESKOVIC***
*Laboratory for Geochemistry and
Gosmochemistry, Deparment of Chemistry, Faculty of Science, University of Nis,
P.O. Box 91, YU-18000 Nis,
**Instituto de Ciencias de le Tierra, Facultad de Ciencias, Universidad Central de Venezuela, Aptdo. 3895, Caracas 1010-A and
***Vinca Institute of Nuclear Sciences, P.O. box 522, YU-11001 Belgrade, Yugoslavia
(Received 10 November
High resolution mass spectrometry indicates that the isotopic abundance of 50vanadium (V) of the Late Cretaceous La Luna petroleum asphaltenes and related source kerogen of marine origin (both highly enriched with V >> 2000 ppm) is higher by about 3,5 % than that of an inorganic vanadium source (VOSO4 > 5H2O, Merck). It is proposed that the difference in the 50V/51V values between the La Luna source kerogen/the associated petroleum asphaltenes and the inorganic source can be best ascribed to the biological processing of seawater V. The fact that the isotopic compositions of V vary over a very narrow range (2.46-2.50) suggest an essentially same (or similar) and fixed bilogical source of V.
Keywords: vanadium, isotope, asphaltene, petroleum.
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More hyperenergetic molecular graphs
JACK H. KOOLEN, VINCENT MOULTON*, IVAN GUTMAN** and DUSICA VIDOVIC**
University of Bielefeld, D-33501 Bielefeld, Germany,
*Physics and Mathematics Department (FMI), Mid Sweden University, sundsvall, S-85170, Sweden and
**Faculty of Science, University of Kragujevac, P.O.Box 60, YU-34000 Kragujevac, Yugoslavia
(Received 4 November
If G is a molecular graph and l1, l2, ..., ln are its eigenvalues, then the energy of G is equal to E(G) = |l1| + |l2| + ... + |ln|. This energy cannot exceed the value . The graph G is said to be hyperenergetic if E(G) >> 2n - 2. We describe the construction of hyperenergetic graphs G for which .
Keywords: total p-electron energy, energy of graph, hyperenergetic graphs.
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On the application of line graphs in quantitative structure-property studies
IVAN GUTMAN and ZELJKO TOMOVIC
Faculty of Science, University of Kragujevac, P.O. Box 60, YU-34000 Kragujevac, Yugoslavia
(Received 10 December
Let G be a molecular graph possessing m0(G) edges. let m1(G) be the number of edges of the line graph L(G) of G, known as the Bertz index. Let m2(G) be the number of edges of the line graph of L(G), etc. We examine the applicability of the sequence mi(G), i = 0, 1, 2, ..., for predicting physicochemical properties of alkanes. Some earlier obtained results are extended and amended.
Keywords: line graph, Bertz index, QSPR, OSAR.
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Contribution to the thermodynamics of 1-(2-thiazolylazo)-2-naphthol in the water-nitrobenzene extraction system
EMANUEL MAKRLIK and PETR VANURA*
Institute of Physical Engineering,
University of West bohemia, veleslavinova 11, 301 14 Pilsen, Czech Republic and
*Department of analytical Chemistry, Prague Institute of Chemical Technology, Technicka 5, 166 28 Prague 6, Czech Republic
(Received 12 January,
revised 12 May 2000)
General relations among thermodynamic parameters characterizing chemical equilibria including species H2A+, HA, H+ and A- in both phases of a two-phase water-nitrobenzene extraction system have been derived. From the extraction measurements, the equilibrium distribution constant of electroneutral 1-(2-thiazolylazo)-2-naphthol (TAN, HA) between the nitrobenzene and aqueous phases has been determined: log KD(HA) = 3.90±0.02. By using this value and further known constants and applying the mentioned relations, the following values of dissociation constants of TAN in nitrobenzene saturated with water have been calculated for a temperature of 25°C: pKdnb(H2A+) = -log Kdnb(H2A+) = 4.9 and pKdnb(HA) = -log Kdnb(HA) = 16.5.
Keywords: 1-(2-thiazolylazo)-2-naphthol, water -nitrobenzene system, distribution constant, dissociation constants.
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Coulometric titrations of bases in propylene carbonate and g-butyrolactone using hydroquinone as the depolarizer and a quinhydrone indicator electrode
LJ. N. JAKSIC*, R. M. DZUDOVIC**, R. P. MIHAJLOVIC** and Z. D. STANIC**
*Faculty of mining and Geology,
University of Belgrade and
**Faculty of Science, University of Kragujevac, Kragujevac, Yugoslavia
(Received 8 October
1999, revised 11 February 2000)
The application of hydroquinone for the coulometric generation of hydrogen ions in propylene carbonate (PC) and g-butyrolactone (GBL) is described. The current-potential curves recorded for theid sepolarizer, titrated bases, indicator and the solvents used showed that the investigated depolarizer is oxidized at lower potentials than the oxidation potentials of other components in the solution. the hydrogen ions generated by the oxidation of hydroquinone were used for the titration of organic bases (triethylamine, n-butylamine, pyridine, quinoline, aniline, N,N’-diphenylguanidine, piperidine, and 2,2’-bipiridine) in PC and GBL with visual (Crystal Violet as indicator) and potentiometric end-point detection using a quinhydrone electrode as the indicator electrode. The quinhydrone added to the to be analyzed solution served both as a source of hydrogen ions and, together with the immersed platinum electrode, as a quinhydrone electrode. The relative error of the determination of the bases was about 1 %.
Keywords: propylene carbonate, g-butyrolactone, coulometric titrations, hydroquinone, base, quinhydrone electrode.
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Kinetic determination of Se(IV) in pharmaceutical samples
S. S. MITIC, J. I. VUCETICb#, S. M. MILETIC and D. A. KOSTIC
Department of Chemistry, University
of Nis, YU-18000 Nis and
*Faculty of Chemistry, University of Belgrade, YU-11001 Belgrade, Yugoslavia
(Received 9 December
1999, revised 1 April 2000)
A kinetic method is described for the determination of Se(IV) based on its inhibiting effect on the Fe(III) catalysis of the oxidation of C6H5COONa with hydrogen peroxide. The detection limit is 0.06 µg cm-3. The relative error ranges between 2.1 and 9.5 % for the concentration interval 0.26 to 2.6 µg cm-3. Kinetic equations are proposed for the investigated process. The effects of certain foreign ions upon the reaction rate were determined in order to assess the selectivity of the method. the method was applied for the determination of Se(IV) in pharmaceutical samples.
Keywords: kinetic method, Se(IV), pharmaceutical samples.
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Effects of methyl oleate and tween 80 on the antibiotic productivity and the fatty acid composition of the total lipids of Streptomyces hygroscopicus CH-7
GORDANA GOJGIC-CVIJOVIC, IVANKA KARADZIC* and JOVAN VUCETIC**
Institute for Chemistry, Technolgy
and Metallurgy, Center for Chemistry, Njegoseva 12, YU-11000 belgrade,
*Institute for Chemistry, Faculty of Medicine, University of Belgrade, Visegradska 26, YU-11000 Belgrade and
**Faculty of Chemistry, University of Belgrade, Studentski trg 16, YU-11000 Belgrade, Yugoslavia
(Received 5 November
The effects of methyl oleate and Tween 80, hexaene H-85 production stimulators, on the fatty acid composition of the total lipids of S. hygroscopicus CH-7 were investigated. Besides oleic acid in the biomass, an increase of the branched chain fatty acid contents was observed: from 1.6 to 2.1 fold in the medium with methyl oleate and 2.5 - 2.9 in the medium with Tween 80 compared to the base medium. These two additives act differently on the growth of the producing strain and the uptake of valine, an essential nutrient. A decreased proteolytic activity and similar cellular fatty acid profiles indicate that the main effect of the added compounds is to facilitate the excretion of antibiotics to the outer medium, thus increasing biosynthesis.
Keywords: Streptomyces hygroscopicus, methyl oleate, Tween 80, fatty acid(s), polyene antibiotic(s).
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Last Updated december 11, 2000.
For more information contact: SHD@elab.tmf.bg.ac.yu