JSCS Vol 64, No. 9
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Semisynthesis of Taxol®: an improved procedure for the isolation of 10-deacetylbaccatin III
R. N. SAICIC, R. MATOVIC and Z. CEKOVIC
Faculty of Chemistry, University of Belgrade, Studentski trg 16, P.O.Box 158, YU-11001 Belgrade, and ICTM Center for Chemistry, Njegoseva 12, Belgrade, Yugoslavia
17 February, revised 1 April 1999)
From the needles of domestic yew, (Taxus baccata), 10-deacetylbaccatin III (10-DAB) can be isolated in quantities of up to 297 mg per kg of fresh needles. Additional quantities of 10-DAB can be obtained from the extract by NaBH4 mediated reductive hydrolysis of baccatin esters. A four-step procedure converts 10-DAB into taxol in 58% overall yield.
Key words: anti-tumor agents, taxol, natural products, semisynthesis.
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Substitued (E)-b-(benzoyl)acrylic acids suppressed survival of neoplastic human HeLa cells
Z. JURANIC, LJ. STEVOVIC*, B. DRAKULIC**, T. STANOJKOVIC, S. RADULOVIC and I. JURANIC
Institute for Oncology and
*Faculty of Chemistry, University of Belgrade, P.O.Box 158, Belgrade and
**Center for Chemistry ICTM, Belgrade, Yugoslavia
27 January, revised 31 March 1999)
The bacteriostatic activity of some of alkyl substituted (E)-b-(benzoyl)acrylic acids was shown earlier. The aim of this study was to investigate the antiproliferative action of 19 alkyl-, or halogeno-, or methoxy-, or acetamido- substituted (E)-b-(benzoyl)acrylic acids, against human cervix carcinoma, HeLa, cells. Target HeLa cells were continuously treated with increasing concentrations of substituted (E)-b-(benzoyl)acrylic acids during two days. The MTT test was used for assessment of the antiproliferative action of this group of compounds. Treatment of HeLa cells with 4-methyl-, 4-fluoro-, 4-chloro-, 4-bromo- and 4-methoxy- derivatives of (E)-b-(benzoyl) acrylic acid leads to the expression of cytostatic activity against HeLa cells (IC50 were in the range from 31-40 µM). Their antiproliferative action was less than that of the basic compound (E)-b-(benzoyl)acrylic acid whose IC50 was 28.5 µM. The 3,4-dimethyl-, 2,4-dimethyl- and 2,5-dimethyl- derivatives as well as the 4-ethyl- and 3,4-dichloro- and 2,4-dichloro-derivatives, have stronger cytostatic activity than the correspoding monosubstituted and parent compound. Their IC50 were 18.5 µM; 17.5 µM; 17.0 mM; 17.5 µM; 22.0 µM and 18 µM, respectively. The 4-iso-propyl- and 4-n-butyl-derivatives exerted higher cytostatic activity than the compounds with a lower number of methylene -CH2- groups in the substitutent. Their IC50 were 14.5 µM and 6.5 µM respectively. The 2,5-di-iso-propyl- and 4-tert-butyl-derivatives expressed the most strong antiproliferative action against the investigated HeLa cells, IC50 being 4.5 µM and 5.5 µM, respectively. The investigated compounds affected the survival of HeLa cells, expressing a strong structure-activity relationship of the Hansch type.
Key words: benzoylacrylic acids, HeLa cells, cytotoxicity, QSAR.
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A polymeric oxovanadium(IV) pyromellitate complex
DUSANKA D. VASOVIC and DJORDJE STOJAKOVIC
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P.O.Box 494, YU-11001 Belgrade, Yugoslavia
9 March 1999)
The reaction of oxovanadium(IV) sulphate with 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid) in the presence of potassium carbonate yields a polymeric complex, K2[VO(pyr)]·6H2O (I) [pyr = pyromellitate(4-) ion]. The PM3(tm) calculations and IR spectroscopy suggest that the polymeric structure of I consists of -V-pyr-V-pyr- chains formed by the 1,4- or 1,5-bridging by the pyr ions. The chains are additionally cross-linked by the chelate function of one of the COO- groups of the pyr ion. Magnetic measurements do not reveal the presence of antiferromagnetic coupling between the V centers.
words: oxovanadium(IV) complexes, pyromellitic acid, polymeric structure,
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A study of the effect of ammonia gas on the solid mono- and dinuclear oxorhenium(V) complexes
M. M. MASHALY
Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt
15 December 1998, revised 11 March 1999)
The reaction of ammonia gas with the solid oxorhenium(V) complexes [Re2 O3L2Cl4]·2H2O, [Re2O2L3Cl6]·2H2O, [ReOLCl(OH2)3]Cl2, [ReOL2(OH2)3]CCl3, [ReOLCl3(OH2)], [ReOL(SCN)2Cl(OH2)]·H2O and [ReOL(SCN)Cl2(OH2)] (where L = 2-benzimadazolethione), yielded the corresponding ammine and/or amine complexes, [Re2O3L2(NH3)2(NH2)2]Cl2 (I), [Re2O2L3(NH3)2(NH2)4]Cl2 (II), [Re2O3L2(NH3)2 (NH2)4]·H2O (III), [Re2O3L4(NH2)4] (IV), [Re2O3L2(NH3)2(NH2)4C (V), [Re2O3L2(SCN)4(NH3)2] (VI) and [Re2O3L2(Thio)2(NH2)4] (VII), respectively, (Thio = thiourea) where ammonia gas has replaced other ligands such as chlorine and water. In complex VII thiourea replaced the thiocyanate group in the start complex through its reaction with ammonia gas. The obtained ammine and/or amine of rhenium(V) complexes have been observed to decompose through several isolatable, as well as non-isolatable complex species as intermediates during heating. [Re2O3L4], [Re2O3L2(NH2)4] and [Re2O3L2(SCN)4], were synthesized pyrolytically in the solid state from the corresponding parent oxorhenium complexes. The electronic absorption spectra and magnetic moments of the complexes show that the Re(V) cation has an octahedral configuration. IR,1H-NMR spectroscopy, conductivity measurements and thermal analysies show that ammonia and thiourea behave as neutral monodentate ligands, SCN- and NH2- as monodentate monoanionic ligands, the organic ligand (L) as a neutral monodentate or bidentate ligand towards the metal cation.
words: ammine and amine complexes, synthesis, magnetic properties,
electrical conductivity, 1H-NMR,
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Protonation constants of hydroxybenzenes in hydrochloric acid
D. S. VESELINOVIC, M. V. OBRADOVIC* and S. B. TOSIC*
Department of Physical Chemistry,
Faculty of Science, Studentski trg 12-16, P.O.Box 550, YU-11001 Belgrade and
*Chemistry Department, Faculty of Philosophy, YU-18000 Nis, Yugoslavia
30 September 1998, revised 23 March 1999)
The absorption spectra of monohydroxybenzene (Fen), 1,3-dihydroxybenzene (Rez), 1,4-dihydroxybenzene (Hi), 1,2,3-trihydroxybenzene (Pg) and 1,3,5-trihydroxybenzene (Fg) in aqueous solutions of hydrochloric acid with different values of the Hammett acidity function(H0) have two absorption bands in the region between 190-220 nm and 260-290 nm. This behavior is similar in another mineral acids (H2SO4, H3PO4, HClO4). The absorbance decreases with increasing of acidity (with decreasing of H0 values) because of O-protonation. The absorption maxima shift to longer wavelengths, and the graphic dependence of the absorption of the second band as a function of H0 gives characteristic S-curves. These curves show the different effect of the acid on the form the protonation of the investigated hydroxybenzenes. The potonation constants of the hydroxybenzenes were calculated: pKFen=-1.95; pKRez=-2.40; pKHi= -1.93; pKPg=-2.95; pKFg=-1.83.
words: hydroxybenzenes, Hammett acidity function, hydrochloric acid,
protonation, UV spectra, S-curve, protonation constant.
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Mechanism and kinetics of the electrosorption of sulphate anions on the (111) face of silver
B. M. JOVIC, D. M. DRAZIC* and V. D. JOVIC**
Institute of Technical Sciences
SASA, P.O.Box 745, YU-11001 Belgrade,
*Institute of vElectrochemistry ICTM, P.O.Box 815, YU-11001 Belgrade and
**Center for Multidisciplinary Studies, University of Belgrade, P.O.Box 33, YU-11030 Belgrade, Yugoslavia
25 April 1999)
The processes of adsorption of sulphate anions onto the (111) face of silver have been investigated by analysis of the cyclic voltammetry and potentiostatic pulse results. It was shown, by fitting the experimentally recorded q - E dependences, that the adsorption of anions follows Frumkin adsorption isotherm. The adsorbed structure was found to be less dense than expected for the dense packed anion monolayer and the process was characterized by high value of the interaction parameter and the Gibbs energy of adsorption (f = 16.5 and DG°ads,q->0 = - 64 kJ mol-1). From the slope of the Ep,a - log (c0) dependence it was concluded that complete charge transfer between the adsorbed anions and the silver substrate occurs. This is supported by the Ep,a - log v linear dependence in the region of high sweep rates (v > 10 V s-1) with rational value of line slope (~ 60 mV dec-1) which is possible only if the complete charge transfer reaction occurs. The electrosorption process of sulphate anions was found to be complex electrochemical reaction, taking place through three steps. It was proposed that the rate-determining step is the second step, i.e., the electrochemical formation of (SO4)ads species.
Key words: (111) face of silver, sulphate anions, complete charge transfer, Frumkin adsorption isotherm, mechanism and kinetics of electrosorption.
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Single crystals of bismuth silicon oxide grown by the Czochralski technique and their characterisation
ALEKSANDAR GOLUBOVIC, SLOBODANKA NIKOLIC, RADOS GAJIC*, STEVAN DJURIC** and ANDREJA VALCIC***
Institute of Chemistry, Technology
and Metallurgy, Njegoseva 12, YU-11000 Belgrade,
*Institute of Physics, Pregrevica 118, P.O.Box 57, YU-11001 Belgrade,
**Faculty of Mining and Geology, Djusina 7, P.O.Box 162, YU-11000 Belgrade, and
***Faculty of Technology and Metallurgy, Karnegijeva 4, YU-11000 Belgrade, Yugoslavia
23 November 1998, revised 11 May 1999)
Single crystals of Bi12SiO20 were grown by the Czochralski technique. The critical diameter and the critical rate of rotation were calculated. Suitable polishing and etching solutions were determined. X-Ray measurements were performed on powdered samples to obtain the lattice parameters. The optical properties of the bismuth silicon oxide single crystals were investigated. The obtained results are discussed and compared with published data.
Key words: bismuth silicon oxide single crystals, Czochralski technique, critical diameter, ciritical rate of rotation, etching solution, optical properties.
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Copyright & copy; SHD 1999.
Last Updated September 8, 1999
For more information contact: SHD@elab.tmf.bg.ac.yu