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p. 200-207
Received: 2 February 2000 / Accepted: 14 February 2000 / Published: 1 March 2000
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| Download PDF Full-text (36 KB) Abstract: New derivatives of 3,5-disubstituted 4H -Pyran-4-one podands (9-15) were prepared by transesterification reaction of dimethyl or diethyl 2,6-dimethyl-4H -pyran-4-one-3,5-dicarboxylate with some glycol, glycol ethers or by nucleophilic substitution of some phenols or glycol ethers with 3,5-bis (bromomethyl)-2,6-diphenyl-4H -pyran-4-one.
p. 208-218
Received: 8 March 1999 / Accepted: 28 February 2000 / Published: 3 March 2000
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| Download PDF Full-text (41 KB) Abstract: A group of 26 new 2-halogeno-6-alkylsulfanyl- and 2,6-bis-alkylsulfanyl-4-amidopyridines and corresponding thioamidopyridines was synthesised. Some of the amidopyridines and all thioamidopyridines were tested for their antimycobacterial activity against atypical mycobacterial strains. Promising photosynthesis-inhibiting activity was also found for some of the amidopyridines.
p. 219-226
Received: 17 February 2000 / Accepted: 28 February 2000 / Published: 2 March 2000
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| Download PDF Full-text (60 KB) Abstract: The detailed structure of methyl 4-acetamido-4-cyano-4,6-dideoxy-2,3-Oisopropylidene-ß-D-allopyranoside was established by X-ray analysis confirming allo configuration at C-4 and suggesting a 4 C1 conformation of the pyranose ring. The values of relevant torsion angles and calculated puckering parameters revealed a distortion into the direction of 0 H 5 , thus indicating a flattening at C-1 and C-4.
p. 227-239
Received: 9 February 2000 / Accepted: 29 February 2000 / Published: 3 March 2000
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| Download PDF Full-text (122 KB) Abstract: A conformationally rigid polyheterocycle (3) which mimics the putative receptorbound conformation of dihydropyridine-type calcium channel modulators is prepared in a seven-step reaction sequence based on a Biginelli-type cyclocondensation reaction.
p. 240-244
Received: 11 November 1999; in revised form: 23 February 2000 / Accepted: 6 March 2000 / Published: 14 March 2000
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| Download PDF Full-text (26 KB) Abstract: A convenient mild protocol for oxidation of highly hindered electron rich benzhydrols using DDQ / PbO2 has been developed.
p. 245-251
Received: 10 February 2000 / Accepted: 14 March 2000 / Published: 16 March 2000
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| Download PDF Full-text (69 KB) Abstract: 1-Methyl-10-nitro-11-phenyl(2-furyl)-2-aza-13-oxa-tricyclo[7.3.1.03,8 ]trideca-3,5,7-trienes 3 were synthesized via the reduction of the aromatic 2-nitro group of 2-methyl-5-nitro-6-(2-nitrophenyl)-4-phenyl(2-furyl)tetrahydropyranols 2 and subsequent condensation with their anomeric OH group. As by-products, the corresponding 6-(2-aminophenyl)-2-methyl-5-nitro-4-phenyl(2-furyl)tetrahydropyranols 4 were isolated.
p. 252-282
Published: 22 March 2000
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| Download PDF Full-text (122 KB) Abstract: This Paper is downloadable at http://www.mdpi.org/molecules/papers/50300252.pdf
p. 283-284
Published: 22 March 2000
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p. 285-288
Published: 22 March 2000
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p. 289
Published: 22 March 2000
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p. 290-292
Published: 22 March 2000
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| Download PDF Full-text (23 KB) Abstract: The use of enzymes in organic solvents has acquired a special relevance in organic synthesis, and lipases are the enzymes most commonly used in transesterication reactions. In the past few years, we have shown the utility of enzymatic aminolysis and ammonolysis reactions for the preparation of amides and for the resolution of esters and amines. The enzymatic alkoxycarbonylation reaction is of great utility in chemoselective reactions of natural products. Lipases, enzymes much less exploited in organic synthesis, have an increasing interest, especially the use of (R )-oxynitrilases for the synthesis of optically active cyanohydrins.
p. 293-298
Published: 22 March 2000
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| Download PDF Full-text (56 KB) Abstract: The preparation of a variety of novel aziridine-γ-lactones (3) from carbohydrates is described. In contrast to aziridine-2-carboxylates, the lactones react regiospecifically at C-2 with soft nucleophiles to provide optically pure substituted β-amino acid precursors. Hard nucleophiles react exclusively at the C-3 position to provide α-amino acid precursors. The utility of this methodology was demonstrated by the preparation of (3S,4S)-dihydroxy-L-glutamic acid (DHGA) from the appropriate aziridine-γ-lactone. DHGA was subsequently shown to be a selective partial agonist of mGluR1 receptors. A more concise preparation of aziridine-γ-lactones was achieved by 1,4-Michael addition of benzylamine to 2-O-triflylbutenolides. Use of a 2-O-mesylbutenolide led, under the same conditions, to the corresponding aziridine-2-carboxamides or 2-carboxylates. Finally, a new Evanstype aziridinating agent, Ses-iminoiodinane, was developed and shown to react efficiently with unsaturated substrates to give the corresponding aziridines, whose N-Ses protecting groups can be removed under mild conditions.
p. 299-301
Published: 22 March 2000
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p. 302-303
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Autochthonous species of the Calceolaria (Scrophulariaceae) genus are studied. From their apolar extracts 55 new diterpenes of six skeleton types, naphtoquinones and flavonoids have been isolated. Among the different diterpenes malonic substitutions and bis-diterpenes in which both units are joined by a malonic acid unit stand out. Pimaranes present C-9 epimerisation and, consequently, H-9 has the same orientation as Me-20. From C.sessilis naphthoquinones with antichagasic activity have been isolated; and the biotransformation of 2α,19-dihydroxy-9-epi-entpimara-7,15-diene with Giberella fujikuroi produced 7 new diterpenes.
p. 304-306
Published: 22 March 2000
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p. 307-308
Published: 22 March 2000
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p. 309-310
Published: 22 March 2000
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p. 311-312
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The results of three years of search for natural aromatase inhibitors will be presented.
p. 313-314
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The synthesis of new anthelmintic compounds derived from 2-amine-4-hydroxy-δ-valerolactams and 2,4-dialkylthiazoles is described. The synthetic procedures and biological activity data for these compounds will be presented.
p. 315-316
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Endogenous derivatives of biogenic amines, such as phenethylamines, indolalkylamines and harmines, have been extensively studied as usual constituents of body fluids. Methylated derivatives of indolalkylamines have been also related to mental disorders, e.g. schizophrenia and hallucination.
p. 317-318
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Different physicochemical properties such as solute-solute and solute-solvent interactions, tautomerism, lipophilicity and solubility in water were determined for a serie of 6,7-diaryl-pteridines in order to relate those properties with their nematocide action.
p. 319-320
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: Use of the AlCl3 –L reagent in the regioselective acylation of benzodioxinic derivatives. Spectroscopic studies show the presence of coordination compounds as reaction intermediates, being the responsible of the observed regioselectivity.
p. 321-322
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: We are describing a brief stereospecific synthesis of a model compound related to Saudin, with a lactone ketal backbone present in the natural product starting from a tricyclic epoxiketal.
p. 323-324
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: An empiric rule derived from the analysis of the 13 C NMR spectral data, allowed us to determine 5,6-epoxide stereochemistry on decalinic systems and a discussion of the scope and limitations of this rule and its extension to other carbon squeletons, is presented.
p. 325-326
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: 3β-hidroxyilicic alcohol was obtained from of ilicic alcohol using cultures of Aspergillus niger .
p. 327-329
Published: 22 March 2000
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| Download PDF Full-text (20 KB) Abstract: Olefination reactions directed to the synthesis of cassiol from compounds 2-5 will be discussed.
p. 330-331
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: Molecular Connectivity is a method, which allows to discriminate different pharmacological activities on the basics of numeric parameters of the molecules in study, related with specific and exclusive indexes. In the present study, we propose two potentially anti-neoplasic compounds: tricromil and zomepirac , by analyzing more than a hundred different chemicals.
p. 332-333
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: A series of clay minerals, HB, NB and Al-PILC have been studied in the alkylation reactions of 2-octanol with phenol at 180°C, under conditions of alcohol/phenol = 1 (mole ratio) and W/FA o °= 64,27 ghmol-1. The selectivity of Al-PILC was 77,12% for octyl phenol and 16,5% for dioctyl phenol.
p. 334-335
Published: 22 March 2000
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| Download PDF Full-text (21 KB) Abstract: During the last years, many bisbibenzylic macrocyclic ethers were isolated and identified in Hepaticae . One of them is MARCHANTINQUINONE, a quinonic macrocycle with interesting biological activity. In the following report, we present the last steps of the total synthesis.
p. 336-337
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The epoxidation of limonene with hidrogen peroxide was studied over zeolite Tibeta (a large pore material) and heteropoly acids on carbono and alumina supported. PW11 /C was catalyst the best tested.
p. 338-339
Published: 22 March 2000
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p. 340-341
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The solubility in water and the partition coefficients, K, in soils samples of residues of petroleum of different ages were determined using an organic cosolvent (methanol), and the solvophobic theory was applied for the interpretation of results. The behavior of the residuals turned out to be dependent of the cosolvent fraction. The values of K’s vary among 900 (Lkg-1 ) and 2,900 (Lkg-1 ) showing a general and marked increase for residues of increasing age. The determined parameters are useful for the modeling of environmental impact in polluted soils.
p. 342-344
Published: 22 March 2000
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| Download PDF Full-text (19 KB) Abstract: The formation of an inclusion compound between a naphthoquinone derivative (I) and HP-ß-CD was studied in solid state by X-ray diffractometry, DSC, and IR.
p. 345-347
Published: 22 March 2000
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| Download PDF Full-text (20 KB) Abstract: Cultures of the fungus epibiont from the herbaceous shrub B. coridifolia yielded four macrocyclic trichothecenes. As these toxins are the same as those found in B. coridifolia , the relationship between the plant and the epibiont must be considered as mutualistic.
p. 348-349
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: Five disulfated steroids and a mixture of monosulfated steroids were isolated from the ethanolic extract of the antarctic ophiuroid Gorgonocephalus chilensis . The structures were determined by 1 H-NMR, 13 C-NMR and FABMS.
p. 350-351
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: Purification of the ethanolic extract of the starfish L. annulatus led to the isolation of two sulfated glycosides and a pentahydroxylated steroid. One of the saponins contains a novel pentasaccharide chain attached to C-6 of the steroidal aglycone.
p. 352-353
Published: 22 March 2000
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| Download PDF Full-text (14 KB) Abstract: Cytotoxic fractions obtained by purification of the ethanolic extract of Anasterias minuta contain sulfated hexasaccharide glycosides. These compounds show antifungal activity against Cladosporium cucumerinum .
p. 354-355
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: A screening of metabolites guided by antimicrobial and citotoxic bioassays was conducted with several fungi. The bioactive compounds were isolated and identified from the active extracts.
p. 356-357
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: Microbial hydroxylation of tedonodiol, an eremophilane alcohol, was carried out with Aspergillus niger cultures, yielding the 2α - hydroxyderivative.
p. 358-359
Published: 22 March 2000
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| Download PDF Full-text (13 KB) Abstract: Kinetics of the synthesis of 3-[3-quinoxaline(1H)-one]propionic acid (I) were performed. This compound was achieved from reaction between o-phenylenediamine and α-ketoglutaric acid under different experimental conditions, and it was sent to the National Cancer Institute (USA) for its pharmacological evaluation.
p. 360-361
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The thermal decomposition reaction of cyclic organic peroxides was studied in toluene solution in a wide temperature range. The kinetic data show an important substituent effect on the unimolecular homolysis of the O-O bond of these molecules.
p. 362-364
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The kinetics of the thermal decomposition reaction of cis-6-phenyl-5,6-(2-phenyl-propilydene)-3,3-tetramethylene-1,2,4-trioxacyclohexane (I) was investigated in the temperature range of 100-130°C in selected solvents of different physicochemical properties to evaluate a solvent effect on the reaction.
p. 365-366
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The thermal decomposition reaction of acetophenone cyclic diperoxide (trans-3,6-dimethyl-3,6-diphenyl-1,2,4,5-tetroxane; APDP) at the initial concentration of c.a. 0.01 mol kg-1 and temperature ranges of 135.5 to 185.0° C has been investigated in dioxane and acetonitrile solutions, and in an 2-propanol/benzene mixture.
p. 367-369
Published: 22 March 2000
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| Download PDF Full-text (30 KB) Abstract: Four brassinosteroids analogs of homoteasterone and homotyphasterol bearing 5α-OH and 5α-F groups have been synthesized and their bioactivities evaluated.
p. 370-371
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: Several polyfunctional carbonyl compounds, such as α- and β-ketoesters, were chemo- and stereoselectively reduced by Mucor rouxii cultures in water and in organic solvents. Results show that reductions can be carried out in a variety of organic solvents.
p. 372-373
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: Lipases from different sources catalyze the polyesterification of glycerol and several dicarboxylic acids in presence or organic solvents
p. 374-375
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The nitration of Phenothiazine (PHEN) in acetonitrile (ACN) in the presence of excess NaNO2 has been studied in detail. First, the electrochemical behavior of the reactants was investigated by cyclic voltammetry to determine the electrolysis conditions. Controlledpotential electrolysis was used for the electrosynthesis.
p. 376-378
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: Seeds from Passiflora caerulea were defatted with n-hexane yielding 29,9% of crude oil (dry basis). The crude oil was examined in their physicochemical characteristics. Fatty acid composition value showed only three acids in significative proportion: 16:0, 18:1 and 18:2. The residual seed meal analysis included: moisture value, ash, metals content, sugars, crude fiber, protein and available lysine.
p. 379-380
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The photodynamic effect of 5,10,15,20-tetrakis(4-methoxyphenyl)porphine (TMP) on Hep-2 cell line is reported. The incorporation of TMP was analyzed at different times and photosensitizer concentrations. The irradiation of cell cultures produces cell mortality, while no toxicity was observed in dark condition.
p. 381-382
Published: 22 March 2000
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| Download PDF Full-text (14 KB) Abstract: The nucleophilic bimolecular substitution on 1,2:3,4-di-O -isopropylidene-α-Dgalactopyranose with NH2 -heterocyclic derivatives allows us to obtain some new compounds with potential biological activities. The characterization of them as well as a discussion of their reactivities toward sulfur analogues are present.
p. 383-385
Published: 22 March 2000
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| Download PDF Full-text (21 KB) Abstract: Two series of diesters with bend-rod shapes were synthesized and their thermal properties characterized by POM and DSC. The central group conformational mobility and polarity as well as the length of the mesogenic groups were varied in order to correlate these parameters with mesophase stability. Results indicate that series II diesters are enantiotropic and that their mesophase sensitivity to central group structural changes is limited.
p. 386-387
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: Two new labdane-type diterpene glycoside, were isolated from the flowers of Baccharis medulosa DC (Asteraceae). Structures of these compounds were established by application of various spectroscopic techniques.
p. 388-390
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: In the present work we report the results obtained in the reaction of β-stannylketones (I) with t -BuONa in dimethylsulfoxide (DMSO) and acetonitrile (ACN) as solvents. The reaction mechanisms probably involved are proposed.
p. 391-392
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: The addition reaction of triorganotin anions to α,β-unsaturated nitriles leads to α-alkyl-β-stannylnitriles with high diastereoselectivity.
p. 393-395
Published: 22 March 2000
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| Download PDF Full-text (20 KB) Abstract: Under high pressure conditions, the Diels-Alder reaction involving N,N-diethyl-1-tosyl-3-indoleglyoxylamide and 1-(N-acetyl-N-propylamino)-1,3-butadiene produces a highly functionalized intermediate for the synthesis of Indole Alkaloids, in shorter times and higher yields than under thermal conditions.
p. 396-397
Published: 22 March 2000
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| Download PDF Full-text (19 KB) Abstract: The synthesis by dehalogenating polycondensation and characterization of a new soluble conjugated polymer, poly(m -pyridylene-1,2-diphenylvinylene), DP-PPyV, is reported here. It shows good mechanical properties and a λmax = 330 nm. The maximum intensity peak of MALDI-TOF corresponds to 1.800 Da.
p. 398-400
Published: 22 March 2000
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| Download PDF Full-text (21 KB) Abstract: The analysis of fluorescence spectra of a set of structurally related AMFQ let to identify the effects of structural changes and the presence of electric charge generated by acid-base reaction on the emission spectra.
p. 401-402
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The kinetics of the reaction of 2,4-dinitrochlorobenzene (DNClB) with aniline and substituted anilines such as p-anisidine, p-toluidine and N-methylaniline have been studied in toluene. Except for N-methylaniline the reactions have shown a third order in amine rate dependence which is consistent with aggregates of the amine acting as the nucleophile. On the other hand, the reaction of DNClB with N-methylaniline under the same conditions shows a linear dependence of the second order rate coefficient, kA , vs [amine], which is consistent with the previous mechanism.
p. 403-404
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: the utilization of substitued dienes with electron-donor groups and under high pressure conditions, induces the dienophilic character of 1-nitronaphtalene in Diels-Alder reactions, giving the products with and without the nitro-group, the yield depending on the nature of the dienes substituent groups.
p. 405-406
Published: 22 March 2000
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| Download PDF Full-text (19 KB) Abstract: HPCD inhibits the hydrolysis reaction of monoamides and monoesters of phthalic and maleic acid at pH 2. The magnitude of inhibition depends on the leaving group. For some of the substrates, the reaction in the cavity is more than 100 times slower than that in solution.
p. 407-408
Published: 22 March 2000
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| Download PDF Full-text (14 KB) Abstract: The kinetics of the hydrolysis of phenyl perfluorooctanoate was studied at pH 6.00 and 9.90 in water. The substrate is aggregated under all working reaction conditions, which is indicated from the decrease in the reaction rate when the substrate concentration is raised. The addition of β-cyclodextrin produces the deaggregation of the ester catalyzing the reaction.
p. 409-410
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: A conformational study of three new AZT derivatives was made by semiempirical methods in order to find a structural correlation between these derivatives and AZT.
p. 411-412
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: A computational study was performed in order to rationalize the high exo stereoselectivity in the cycloaddition reactions of sugar-derived dienophiles with cyclopentadiene.
p. 413
Published: 22 March 2000
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p. 414-415
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Several stilbenes and styrenes have been treated with heteropolyacid] (HPA) supported over silice. The compounds obtained were characterized by 1 H and 13 C- NMR and the yields were compared with those obtained using H2 SO4 (c) and ethyl poliphosphate] (PPE).
p. 416-417
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The acid -promoted [3+2] cycloaddition of alkenes with benzhydrylic alcohols afford products in good yield and with remarkable stereoselectivity.
p. 418-419
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The synthesis of some isoxazolic compounds from carbohydrate derivatives is described. These products are obtained by 1,3-dipolar cycloaddition reaction and their functionalization leads to derivatives with potential biological activities.
p. 420-421
Published: 22 March 2000
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| Download PDF Full-text (13 KB) Abstract: NMR studies of bioactive semicarbazones are described.
p. 422-423
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: Antifeedant activity of the 4-deoxi-27-hydroxi-withanolides (1, 2 y 3) isolated from Jaborosa integrifolia (Solanaceae) was investigated in caterpillar Spodoptera littoralis on Leaf Disk Choice Bioassay. Results indicate that the best feed inhibition effect is due to Jaborosalactone A.
p. 424-425
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: The effect of the solvent and the substituents on the UV spectroscopic properties of substituted benzophenones was studied.
p. 426-427
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The pKa of monohydroxylated benzophenones was determined by UV spectroscopy. The values obtained are coherent with the resonant forms and hydrogen bond intramolecular of the analyzed compounds.
p. 428-430
Published: 22 March 2000
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| Download PDF Full-text (24 KB) Abstract: A new series of 4-aryl and 4-alkyl-4-N-arylamine-1-butenes (homoallylamines) were synthesized and some of them transformed to 4-aryl or alkylquinolines. All of them showed strong antifungal activities against human pathogenic fungi in vitro , being Epidermophyton floccosum the most susceptible species.
p. 431-432
Published: 22 March 2000
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| Download PDF Full-text (19 KB) Abstract: The photostimulated reaction of Me3 Sn- ion with mono, di and trichloro arenes in liquid ammonia gave very good yields of stannanes by the SRN 1 mechanism. These products reacted by a palladium-catalized cross coupling reaction with halobenzenes to give phenylated products also in very goods yields. Similar yields can be obtained in one-pot reactions.
p. 433-434
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The extracts and sesquiterpene lactones of S.argentinum were assayed to determine their biological activity on Artemia salina . The most active compound was costunolide (1) with LD50 = 62 ppm.
p. 435-436
Published: 22 March 2000
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| Download PDF Full-text (14 KB) Abstract: Phytotoxic Activity of the 6-acetyl-5-hydroxy-2isopropenyl-2,3-dihydrobenzofurane (1) isolated from Trichocline reptans (Asteraceae ) was investigated in two weed species. Results indicate that the best growth inhibition effect ocurres on Chenopodium album weed. Phythotoxic effect of the T. reptans chloroformic extract and of the benzofurane are discussed and compared in the two weed species.
p. 437-438
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: From the effect of β-cyclodextrin and hydroxypropyl-β-cyclodextrin on the UVvisible and fluorescence spectra of carbaryl and carbofuran, the values of association constants were determined. The ratio of the fluorescence quantum yields for the bound and free substrates indicated an enhanced fluorimetric method of detection.
p. 439-440
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The syntheses of trineophyl- (1a) and tri-(-)-menthylstannyl phenylacetylene (1b) as well as that of (E)-1-trineophylestannyl-2-phenylethene (2) and (E)-1-trineophylstannyl-1,2-diphenylethene (3) are described. The hydrostannation of 1a with an excess of trimethyltin hydride led to 1,1,1-tris(trimethyltin)-2-phenylethane (4) and/or 1,1-bis(trimethyltin)-2-phenylethene (5) depending on the reaction conditions.
p. 441-442
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: From whole Jaborosa odonelliana plants four new withanolides containing a spiranic lactone in the side chain, were isolated and their structures elucidated by spectroscopic methods.
p. 443-444
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: 11α,12α-aziridinosteroids (2a, b, c) were prepared from 5β-H-11-pregnene-3,20-dione (1) using different iminophenyliodinanes and cloramine aziridination reagents.
p. 445-446
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: We report a study of 3,3-dimethyl substituted acylthioureas. X ray data and quantum mechanical calculations demonstrated that the "S" conformation is the most stable both for the acylthioureas and the corresponding anions. The high regioselectivity towards S-alkylation is explained on the basis of the localization of the HOMO mainly over the sulfur atom.
p. 447-448
Published: 22 March 2000
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| Download PDF Full-text (20 KB) Abstract: 17(13→18)-Abeo and D-homo analogs of the natural neurosteroid 3α-hydroxy-5αH-pregnan-20-one were prepared by anionic or radical (mercury (II) hydride mediated) rearrangements of steroidal cyclopropylketones respectively.
p. 449-450
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: From the aerial parts of Salpichroa origanifolia a new withanolide in which the C-13 angular methyl has migrated to C-17, was isolated and characterized by spectroscopic methods.
p. 451-452
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: Semiempirical calculations were performed to carry out a conformational analysis for carbohydrate-derived dienophiles 1-4. For α,β-unsaturated carbonylic compounds 2-4, a good correlation between Diels-Alder reactivity with calculated values for LUMO energies was observed.
p. 453-454
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: The Birch alkylation products are very unstable. We are showing, in this communication, the results of a theoretical study that compares different decomposition reaction mechanisms. The conclusions are in agreement with our experimental results.
p. 455-456
Published: 22 March 2000
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| Download PDF Full-text (21 KB) Abstract: The fluorescent excited state of 2-naphtoxide ion is quenched by haloadamantanes (X-Ada) as electron acceptors according to an electron-transfer mechanism. This mechanism is proposed on the basis of:1) decreasing quenching rate constant as the reduction potential of X-Ada is made more negative and 2) the analysis of reaction products.
p. 457-458
Published: 22 March 2000
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| Download PDF Full-text (19 KB) Abstract: The phthalimide anion reacts by the SRN 1 mechanism under photostimulation with different substrates. Whilst with 1-iodonaphthalene only reduction of the naphthyl radical is observed, with 1-iodoadamantane coupling at the carbon instead of at the nitrogen takes place.
p. 459-461
Published: 22 March 2000
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| Download PDF Full-text (20 KB) Abstract: n/a
p. 462-464
Published: 22 March 2000
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| Download PDF Full-text (19 KB) Abstract: Ilicic alcohol, a natural sesquiterpene, was converted into an aldehyde by using Jones’ oxidation. The gastroprotective activity of ilicic aldehyde was evaluated in mice and rats.
p. 465-467
Published: 22 March 2000
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| Download PDF Full-text (19 KB) Abstract: The aim of this work was to evaluate the activity in the gastrointestinal tract of the several extracts and pure components isolated from Bidens species and Zuccagnia puntacta .
p. 468-469
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The regioselective opening of epoxides with organotin oxides 1 and 2, in presence of halogenated alcohols was developed, yielding the halohydrin derivatives.
p. 470-471
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: From the petroleum ether extract of the aereal part of Condalia microphylla Cav, hydrocarbons, sterols, alcohols, and fatty acids were isolated. From fruits of the same plant anthocyanins were also isolated and characterized by chromatographic and spectroscopic methods.
p. 472-474
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: The geometric isomerisation of the title compound induced by bromine or chlorine appears to involve ionic pair species resulting from the nucleophilic attack of the halogen.
p. 475-478
Published: 22 March 2000
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| Download PDF Full-text (21 KB) Abstract: The lipoxygenase-1 (LOX-1) activity of 19 soybean genotypes was quantified in two consecutive years. The LOX-1 activity produced by any cultivar was essentially the same in both, 1995 and 1996 crop years. The lowest values of LOX-1 activity were found in NK 555 cultivar whereas Asgrow 5409 cultivar had the highest values.
p. 479-480
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: The 1 H y 13 C-NMR spectra of some 1,3 and 1,2,3-trisubstituted 1H -4,5-dihydroimidazolium salts are analyzed.
p. 481-482
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: The synthesis of several quinolinimidoacetic acid derivatives (I) by two different routes, starting from quinolinic anhydride or quinolinimide, is described. In all cases better yields and decreased reaction times were achieved employing microwave irradiation as an alternative source of energy.
p. 483-484
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Geometry optimization of 1-(o-nitrophenyl)-2-phenyl-1H-4,5,6,7-tetrahydro-1,3-diazepine is performed by means of molecular modeling. Results are correlated with theoretical and experimental UV spectra.
p. 485-486
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The percentage composition, fatty acids and oxidation stability was obtained from “peanut mayonnaise ” in comparison with commercial mayonnaise and sunflower oil. “Peanut mayonnaise ” showed better chemical quality than commercial mayonnaise.
p. 487-488
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: Antioxidant activity of skin from runner peanut was performed on sunflower refined oil. The skin was obtained from industrial blanching process. The oil was oxidized at 60ºC. The methanolic extracts show antioxidant activity in relation to the oil (without additives). However these extracts do not reach the activity level from BHT.
p. 489-490
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: The electronic structures and conformational studies of the cyclopeptides, O methyl-α-amanitin, phalloidin and antamanide, were obtained from molecular parameters on the basis of semiempiric and ab initio methods.
p. 491-492
Published: 22 March 2000
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| Download PDF Full-text (20 KB) Abstract: The elaboration of a 2,3,7-9a-tetrahydro-1H-8-oxa-1-aza-phenalen-9-one derivative, as a potential key intermediate for the synthesis of stephaoxocanes, employing Jackson’s tosylamidoacetal cyclization, is presented.
p. 493-494
Published: 22 March 2000
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| Download PDF Full-text (21 KB) Abstract: An approach to the synthesis of the isochromane moiety embodying the AC-ring system of the stephaoxocanes, by the use of an Oxa-Pictet Spengler type cyclization strategy, is reported.
p. 495-496
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: A new method for the in situ elaboration of B-alkoxyoxazaborolidines is presented. Their use in the enantioselective reduction of prochiral aromatic ketones provides excellent chemical and optical yields of chiral alcohols.
p. 497-498
Published: 22 March 2000
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| Download PDF Full-text (14 KB) Abstract: Following our work in the synthesis of compounds with antichagasic activity, we describe new potential products in which the same "leader" compound was modulated.
p. 499-500
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: It describes the synthesis of new 1,2,6-Thiadiazin 1,1-dioxide derivatives using condensation of the Knoevenagel type. The products are evaluated in vitro as trypanocidal agents.
p. 501-502
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: It describes the regioselectivity studies of 5,6-Dimethyl-1,2,4-triazine-N4-oxide using different electrophiles.
p. 503-504
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: A new synthesis of 3,4-diphenyl-4-aryl-1,2,5-thiadiazolines 1,1-dioxide through the addition of aromatic derivatives to 1,2,5-thiadiazole 1,1-dioxide is presented. Anhydrous AlCl3 is used as catalyst.
p. 505-507
Published: 22 March 2000
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| Download PDF Full-text (24 KB) Abstract: The synthesis of the acyclic intermediate 7 towards the preparation of cassiol (2) is described. The cyclization of 7 led to 5, a precursor of 2 and to the unexpected product 8.
p. 508-509
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The reaction of 3-aminopyrazole (1) with 1,2-naphthoquinone-4-sulfonic acid sodium salt (2) was studied in different aqueous media. The novel pyrazolylnaphthoquinones synthesized were physical and spectroscopically characterized, including 2D NMR spectroscopy (HETCOR). The possible reaction mechanism is proposed.
p. 510-511
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Inclusion complexation of 1 with HP-β-CD or HP-β-CD:PVP K30 in aqueous solution was spectroscopically studied and the formation constant for a 1:1 complex was determined from these measurements.
p. 512-513
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The distribution of different amines between n-hexane bulk and the micellar pseudophase of AOT reverse micelles were measured by a fluorometric method. An independent method was used to corroborate the incorporation of the amines to the interface. The effect of the amine structure on the binding constant was analysed.
p. 514-515
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: The phytochemical study of two species of Jaborosa caulescens (var. caulescens and var. bipinnatifida ) yielded the four new withanolides 1-4. The structures of the new compounds were determined using a combination of spectroscopic techniques (including 1D and 2D NMR) and Molecular Modeling.
p. 516-517
Published: 22 March 2000
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| Download PDF Full-text (14 KB) Abstract: The complexes between some flavonoids and metals (Co(II), Cu(II), Mn(II), Mg(II), Sn(II)) have been studied by spectrophotometric methods in order to determine the stoichiometry and stability constants.
p. 518-519
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: Fast atom bombardment (FAB) technique was employed to determine the structure of polar lipids from the cellular membrane of Lactobacillus delbruekii ssp. bulgaricus and Streptococcus salivarius ssp. thermophilus . Analysis of spectra provided useful information about the molecular species and aminoacids constituents of the samples.
p. 520-521
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: New analogues of 3-Formyl-4-phenyl-1,2,5-oxadiazole N-oxide (1) are prepared and evaluated as cytotoxic selective agents in hypoxia.
p. 522-523
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: In the present work, we will intend to show that diol I, microbially derived from toluene using Pseudomonas putida 39D, is a suitable synthon for the synthesis of the A-B ring system of forskolin. The functionalization of diol I, to be used as ring-B, and the attempts of ring-A closure, will be disclosed.
p. 524-525
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: The Shelf-Life (SL) of peanut, soybean and corn blend extruded without (A) and with butylhydroxytoluol (B) and extract of Rosmarinum sp (C) was determined. Only B significativaly increased SL. In function of temperature would be defined by: A- SL = e -0.0465x + 5.1762 , B- SL = e -0.0421x + 5.3332 , C- SL = e -0.581x +5.626
p. 526-528
Published: 22 March 2000
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| Download PDF Full-text (22 KB) Abstract: n/a
p. 529-530
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: A convenient procedure for the synthesis of supramolecules bearing carotenoids and fullerene C60 is reported. The amphipathic nature and the high yield of charge separation of these compounds make them candidates in the formation of transmembrane charge gradients.
p. 531-532
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: A convenient procedure for the synthesis of 5-(4-acetamidophenyl)-10,15,20-tris(4-substituted phenyl) porphyrins from dipyrrolomethane is reported. meso -(4-Substituted phenyl) dipyrrolomethanes were obtained in yields of 72-84%. The amide porphyrins were isolated with appreciable yields of 15-17%.
p. 533-534
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Several 2’,3’-di-O-acetylnucleosides (2a-d) were obtained regioselectively through a Candida antarctica B lipase catalyzed alcoholysis.
p. 535-536
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: E. coli BL21 cells were able to synthesize several purine nucleosides from pyrimidine ones. Kinetics and yields of this reaction showed a strong dependence on pH, temperature, reagent concentrations and weight of wet cell paste. Yields over 90% were reached in the synthesis of adenosine.
p. 537-538
Published: 22 March 2000
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| Download PDF Full-text (31 KB) Abstract: The synthesis of 2β-(heterocyclylthiomethyl)penam derivatives on solid support has been developed. Compounds are obtained in good to high yields (based on loading of the original resin). The key step is the solid-phase double rearrangement of the corresponding penicillin sulfoxide.
p. 539-540
Published: 22 March 2000
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| Download PDF Full-text (21 KB) Abstract: The effect of stereoelectronic interactions on coupling constants is shown. The analysis is done with a new approach in which a selected interaction is deleted and the effect over the couplings is analyzed. 1 H-1 H magnetic couplings three and four bonds apart in hydrocarbons are shown.
p. 541-542
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The polysaccharides from cystocarpic Iridaea undulosa , soluble and insoluble in 2M potassium chloride, Cs and Ci, respectively, were treated with alkali and fractionated by precipitation with increasing concentrations of KCl. They were later separated by ionexchange chromatography, to yield fractions enriched in an α-(1→6)-glucan, agaroids and carrageenans.
p. 543-544
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The 75% isopropanol-soluble material from the endosperm of the legume-seed of Gleditsia triacanthos was isolated. The material extracted with boiling water was fractionated by ion-exchange chromatography and characterized. Besides minor amounts of galactomannans, major proportions of arabinans and/or arabinogalactans appear.
p. 545-546
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Chemical components of eight wild species of Arachis were studied. The objectives were to know the chemical composition and establish chemotaxonomic relationships. The results indicate that A. villosa is suitable for breeding program of cultivated peanut. A. monticola and A. batizocoi showed major chemical affinity with A. hipogaea .
p. 547-548
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The cinnamate esters of 3-p-menthanol (trivial name, menthol) (1) and 4(8)-pmenthen-3-ol (trivial name, pulegol) (2) were prepared and their anti-inflammatory activity was measured. Some of the monoterpenoid esters displayed interesting anti-inflammatory activity.
p. 549-550
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: In industry, the bulk free radical polymerization of styrene takes place with the aid of peroxide initiators such as benzoyl peroxide. In this work di- and trimeric cyclic peroxides were used as initiators of the styrene polymerization in order to increase the rate of polymerization and molecular weights simultaneously.
p. 551-552
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: The crude polysaccharide from cystocarpic Callophyllis variegata was fractionated with potassium chloride yielding three minor fractions which precipitated between 0.05-0.10 M KCl, 1.20-1.25 M KCl and 1.80-2.00 M KCl, and a main product soluble in 2.00 M KCl. These fractions were analysed and structural analysis of the major one was carried out by methylation, FT-IR and 13 C NMR.
p. 553-554
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: Aqueous and nonaqueous AOT/n-heptane reverse micelles where characterized by UV-Visible and fluorescence spectroscopy of AO. The study shows the presence of the dimer in aqueous reverse micelles which is not present in the nonaqueous systems. It seems that there is a conversion of the dimer to monomer in the aqueous reverse micelles at high AOT concentration. In the nonaqueous systems, there is only partition of the monomer. The apparent constants of these processes were calculated.
p. 555-556
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: A new conducting polymer was prepared by chemical and electrochemical polymerization of 3,6-dimethylthieno[3,2-b]thiophene. The galvanostatic deposition afforded uniform, adherent and dark blue films of PDMTT. Electrochemical characterization by cyclic voltammetry showed that it can be repeatedly driven between the doped and undoped species with a coulombic efficiency of nearly 100%.
p. 557-559
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: The objective of this work was to obtain information on Amaranthus greggii S. Wats., related to its nutritional value, its agricultural application as leaf vegetable and for animal consumption. The following variables were analyzed: dampness, ashes, protein, mineral, ethereal extract (fat), brute fiber, oxalic acid, nitrates and carbohydrates.
p. 560-561
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The transformation of ethane into aromatic hydrocarbons over Zn-metal- containing zeolites at W/F=10 gh/mol and 550°C was studied in a flow reactor at atmospheric pressure. Zn-metal-zeolite modified the activation mode of the alkane, generating highly reactive intermediates and enhancing the aromatic selectivity.
p. 562-563
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: We wanted to search for new reaction conditions to prepare the title compounds, to be checked later in novel syntheses of heterocyclic compounds. To the best of our knowledge, there was no report in the literature of any well-established method for the preparation of N -(2-phenoxyethyl)anilines 1.
p. 564-565
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: Diosgeninlactone (1), a natural product from Solanum vespertilio, was stereoselectively synthesized in high yield from 3β-hydroxy-5-androstene.
p. 566-567
Published: 22 March 2000
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| Download PDF Full-text (14 KB) Abstract: It is known that current quality requirements require the utilization of natural colorants in the foods. The objective of the present work is to extract the pigment amaranthus from fresh leaves of Amaranthus hypochondriacus L. cv Don Pedro to characterize it through spectroscopic techniques, to be used as natural colorants.
p. 568-570
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: The composition of essential oil of Mutisia friesiana (Asteracae ) was studied. The oil is a complex system in which 127 compounds were identified. The major components are monoterpenes: b-phellandrene, (Z)-β-ocimene, α and β-pinene and sabinene.
p. 571-573
Published: 22 March 2000
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| Download PDF Full-text (20 KB) Abstract: Alkynes and spathulenol were isolated from Conyza albida (Asteraceae); some of the compounds were lethal against Artemia sp. and cytotoxic against KB cells.
p. 574-575
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: A reverse phase high performance liquid chromatographic assay was carried out for the simultaneous determination of two out of three active principles present in a pharmaceutical preparation. This method was developed to assess the quality of the product.
p. 576-577
Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: In the present work we report the antifungal and cytotoxic activities of a neolignan 8.O.4´series. The most active antifungal compounds show a significant cytotoxic effect which might be related.
p. 578-579
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: In the present work, the kinetic behavior of the title reaction in ethyl acetate + chloroform solvent mixtures is studied. The experimental results are compared with previous findings.
p. 580-582
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: We report here the importance of a keto-enol equilibrium of an arylpropanoid series acting as antifungal agents. An interesting relationship between ln MIC, ∆E enolization and net atomic charges was found. Two compounds were synthesized and their MIC evaluated in order to prove the above relationship.
p. 583-584
Published: 22 March 2000
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| Download PDF Full-text (308 KB) Abstract: A study of the molecular interactions between the active sites of RGD (Arg-Gly-Asp) with it Receptor using simultaions is reported. Our calculations indicate that the guanidine-carboxylate complex is energetically favourd with respect to the guanidine-methyl tetrazole complex.
p. 585-586
Published: 22 March 2000
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| Download PDF Full-text (21 KB) Abstract: We report here a conformational study of cyclic flexible compounds (rings with 9-12 members). Two methods of systematic search for the minima were used. The results were compared with those obtained using other exploratory methods.
p. 587-588
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: The present work analyzes the solvent effects upon the solvatochromic response models for a set of chemical probes and the kinetic response models for an aromatic nucleophilic substitution reaction, in binary mixtures in which both pure components are able to form intersolvent complexes by hydrogen bonding.
p. 589-590
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: The electrocatalytic hydrogenation reaction of naringin derivated chalcone is studied. The reaction is carried out with different catalysts in order to compare with the classic catalytic hydrogenation.
p. 591-593
Published: 22 March 2000
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| Download PDF Full-text (28 KB) Abstract: We describe the preparation and photophysical characterization of two model compounds designed to test a new approach for the quantitative determination of Fluorescence Resonance Energy Transfer (FRET) in biological systems. The method enables modulation of FRET by exploiting the unique reversible spectral properties of photochromic diarylethenes and spiropyrans to create switchable energy acceptors.
p. 594-595
Published: 22 March 2000
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| Download PDF Full-text (19 KB) Abstract: Trialkyltin menthones of type 2 are obtained selectively by 1,4-addition of trialkylstannyl lithium to (-)-pulegone. Reduction of 2 with borane in THF using as catalyst the reagent prepared from borane and (S)-valinol gave a mixture of the corresponding trialkyltin alcohols 3 (Me: 84%; n-Bu: 90,6%) and 4 (Me: 16% and n-Bu: 9,4%).
p. 596-597
Published: 22 March 2000
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| Download PDF Full-text (20 KB) Abstract: A experimental study was performed regarding the influence of the base nature and solvent on the reactive intermediate concentration in the base-promoted bissulfonium salts polymerization. Such polymerization reaction is part of a synthetic procedure used to prepare conjugated polymers. In addition, a theoretical study suggest that a one-electron transfer could be involved in the initiation step.
p. 598-599
Published: 22 March 2000
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| Download PDF Full-text (14 KB) Abstract: The addition of Grignard reagents to aldehydes in the presence of chiral aminoalcohols shows a moderate enantioselectivity. The study carried out with a series of ligands allows the correlation between the structural characteristics and their reactivity.
p. 600-601
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: 4-O -Substituted D-glucuronic acid derivatives were synthesized from D-glucose in order to study the regioselectivity of sulfation.
p. 602-604
Published: 22 March 2000
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| Download PDF Full-text (32 KB) Abstract: New organophosphorus insecticides of dialkylsulphoximines derived with activity upon acetylcholinesterase were synthesized. The obtained compounds were characterized by NMR and IR, and anticholinesterase activity and toxicity was measured. A simulation through computer was done in order to establish the relationship between structure and activity.
p. 605-607
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: From the aerial parts of Conyza sophiaefolia a new alicyclic furan diterpene was isolated and characterized as an E-isomer in C6 of centipedic acid. In addition, the new clerodane type diterpene 12-epi-bacchotricuneatin A as well as two known related diterpenoids were identified. The flavone apigenine was also isolated. Structures were determined on the basis of spectroscopic evidence.
p. 608-609
Published: 22 March 2000
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| Download PDF Full-text (28 KB) Abstract: Carbohydrate containing dimeric surfactants were synthesized starting from Dglucose. Three different spacers were used to link the sugar moieties. The critical micelle concentration (CMC) for these new compounds was determined.
p. 610-611
Published: 22 March 2000
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| Download PDF Full-text (17 KB) Abstract: The purpose of this work is the synthesis of 2,3-butanedione (diacetyl) by selective oxidation of 2-butanone (methyl ethyl ketone) in the presence of O2 and H2 O2 30% as oxidants. All the tests were performed over several selective oxidation zeolite catalysts, synthesized and characterized in our laboratory.
p. 612-613
Published: 22 March 2000
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| Download PDF Full-text (16 KB) Abstract: n/a
p. 614-615
Published: 22 March 2000
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| Download PDF Full-text (18 KB) Abstract: n/a
p. 616-619
Received: 26 January 2000 / Accepted: 17 March 2000 / Published: 22 March 2000
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| Download PDF Full-text (15 KB) Abstract: Eight thia- or azasubstituted butyric acid derivatives were prepared and the influence of these substituents on the chemical shifts of the benzene ring carbon atoms was studied.
p. 620-628
Received: 10 February 2000 / Accepted: 14 March 2000 / Published: 22 March 2000
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| Download PDF Full-text (39 KB) Abstract: A symmetrically disubstituted derivative of the highly fluorescing and photostable rubicene was incorporated in a macrocycle using high dilution conditions and a hydroxyrubicene was functionalized with a modified aminobenzo-15-crown-5.
p. 629-636
Received: 8 March 1999; in revised form: 25 November 1999 / Accepted: 30 December 1999 / Published: 10 March 2000
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| Download PDF Full-text (31 KB) Abstract: The preparation of monoarylidene and both symmetrical and unsymmetrical bisarylidene derivatives of piperazine-2,5-dione is described. The use of 1,4-diacetylpiperazine-2,5-dione make it possible to prepare unsymmetrical bisarylidenes. The introduction of a dicyanomethylene moiety into the para position of one of the arylidene groups gave a remarkable deepening in the colour of the resulting compounds 11 and 16.
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