bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biosynthèse de L'Averufine et de la Versicolorine B: Deux Metabolites de L'Aspergillus Versicolor
Authors: Berger Yves , Jadot Joseph 
Published: September 2010

AbstractThe labeling distribution of averufin and versicolorin B produced from (1‐13C) acetate by Aspergillus versicolor was determined by 13C FT NMR. The results support the polyketide hypothesis for averufin and versicolorin B biogenesis. The pattern of versicolorin B indicates a biogenetic relationship with bisfuranoids, sterigmatocystin and aflatoxins.
Chemical studies of marine invertebrates XIX. Glycosidic chain structure of thelothurins A and B, two new saponins from the Indo‐pacific sea cucumber Thelonota ananas Jaeger (Echinodermata)
Authors: Kelecom A. , Tursch B. , Vanhaelen M. 
Published: September 2010

AbstractThe Indo‐pacific sea cucumber Thelonota ananas contains two new triterpene saponins, thelothurins A and B. Both have the same glycosidic chain shown to be 3‐0‐methyl‐β‐D‐glucosyl‐(1→4)‐β‐D‐xylosyl‐(1→4)‐β‐D‐glucosyl‐(1→4)‐2‐0‐X‐3‐0‐methyl‐β‐D‐glucosyl‐(1→3'β‐aglycone A or B) (IA/B), where X is an hitherto unidentified substituent.
L'Utilisation d'orbitales Localisées dans l'Étude Theorique des Molécules III. Les Derivés Heteroatomiques
Authors: Clarisse F. , Leroy G. , Peeters D. 
Published: September 2010

AbstractL'étude de la transférabilité des orbitales localisées et de leurs propriétés a été étendue aux composés hétéroatomiques. Des composés de référence permettent d'établir une systématique tant au niveau des orbitales de liaison qu'à celui des éléments de matrice qui leur sont associés. La transférabilité des éléments de Fock permet d'élaborer une méthode LCLO‐MO paramétrique applicable aux hydrocarbures saturés, insaturés et composés hétéroatomiques. Quelques applications montrent l'intérêt de la méthode.
Conjugative stabilization in organosilicon reactive intermediates
Authors: Heaton Marie , Rogers Pamela Z. , Davis Dennis D. 
Published: September 2010

AbstractMolecular orbital theory is used to study the effects of conformation and geometry on the stabilities of β‐SiR3, (R=CH3, H) substituted‐ethyl cations, radicals and carbanions. Both the radical and cation slightly favor a three‐centered cyclic form over a highly distorted, bisected open form (C‐C‐Si < = 75°), while the anion prefers the open form. The distortion is due to strong interaction between the carbon‐pz and the d‐orbitals on silicon (p‐d homoconjugation). A separation of conjugative effects based upon conformational dependence of hyperconjugation suggests that both hyperconjugative and homoconjugative stabilization are of major importance in stabilizing the cation, whereas the latter appears more important in the radical and anion.Specific‐site solvation of the cation by water shows a large steric effect at silicon and generally responds to charge density at other centers.
Simultaneous determination of yttrium and several rare earths in monasite and bastnaesite by hollow cathode excitation coupled to vidicon detection ‐ A progress report
Authors: Broekaert J. A. C. 
Published: September 2010

AbstractThe detection limits for rare earths (R.E.) obtained when exciting samples in a hot hollow cathode (H.C.) and applying vidicon spectrum registration are compared to previously published photographic results. A hot H.C. coupled to vidicon is applied to the simultaneous determination of yttrium and several R.E. in dissolved monasite and bastnaesite samples.
Synthetic studies on rosane diterpene. Synthesis of (±)‐2β‐hydroxy‐4aβ, 8a‐dimethyl‐8‐methylene‐trans, anti, trans‐perhydrophenanthrene
Authors: Banerjee Ajoy Kumar 
Published: September 2010

Abstract2β‐Benzoyloxy‐4aβ‐methyl‐8‐keto‐trans, anti, trans‐perhydrophenanthrene (Va) has been synthesised which has been subjected to angular methylation followed by Wittig reaction to synthesise the titled compound (II).
Molecular constants of some tetrahedral XY4 molecules
Authors: Mohan S. 
Published: September 2010

AbstractAll the five independent G.Q.V.F.F force constants in nine molecules of the tetrahedral type have been evaluated on the basis of kinetic constants of these molecules. The results appear to show the basic importance of kinetic constants in molecular dynamics. The mean amplitudes of vibration of these molecules have been calculated using the present set of force constants. The kinetic constants, force constants and the mean amplitudes evaluated here, are interesting showing the significance of the new procedure.
Analyse Aux Rayons X de la Structure D'un T. Butyl‐2 Méthyl‐3 Cyclopentane‐Diol‐1,4
Authors: Germain G. , Declercq J. P. , van Meerssche M. 
Published: September 2010

AbstractMolecular configuration determined by direct methods on monoclinic crystals. P1/c. Z=4.
Structures de Deux Dimères Formés a Partir de la 1,2,4‐Triméthylimidazoline‐5‐One
Authors: van Meerssche M. , Germain G. , Declercq J. P. , Bodart‐Gilmont J. 
Published: September 2010

AbstractCrystal and molecular structures are described for meso and dl dimers C12H16N4O2 isolated during the synthesis of the title imidazoline derivative. Crystal data are as follow. dl form: trigonal, R3c; a=16,815 Å, α=116,93°; Z=6. Meso form: monoclinic, P21/c; a‐14,584, b=7,992, c=13,495 Å, β=117, 28°; Z=4.
Alcaloides de Lycopodium Gnidioides et de Lycopodium Verticillatum
Authors: Nyembo L. , Kahindo N. , Braekman J. C. , Hootele C. 
Published: September 2010

AbstractBesides the already known alkaloids lucidioline (I), anhydrolycodoline (II), lycoclavine (III) and selagine (IV), two new compounds have been isolated from Lycopodium gnidioides L.f.: gnidioidine (V) and lycognidine (VI). From L. verticillatum L. anhydroaposerratinine (VII) and lycoverticine (VIII) were obtained. The structures of the compounds (V) to (VIII) have been determined.
N‐Acylamino acids and peptides IV The Synthesis of N‐cinnamyl‐, N‐p.coumaryl‐ and n‐caffeyl‐glycine and ‐glycyl‐l‐phenylalanine
Authors: De Pooter H. , van Rompaey L. , van Sumere C. F. 
Published: September 2010

AbstractCondensation of cinnamyl‐, O‐ethoxycarbonyl‐p. coumaryl‐ or O,O‐diethoxycarbonylcaffeyl chloride with glycine ethyl ester (or t‐butyl ester), and with A‐glycyl‐L‐phenylalanine t‐butyl ester gave acceptable yields of the completely protected intermediate N‐acyl‐esters. The latter substances were then transformed into the title compounds by removal of the blocking functions, the elimination of the O‐ethoxycarbonyl‐group being frequently more easily performed with hydrazine hydrate than with alkali.
The rotameric distribution of 5‐halomethyl groups in 1,3‐dioxanes
Authors: Borremans Frans , Anteunis Marc J.O. 
Published: September 2010

AbstractThe rotameric distribution in the axial and equatorial halomethyl group in the 2‐methyl‐5‐halomethyl substituted 1,3‐dioxanes is determined qualitatively and a rationale is proposed. The data indicate an attractive 1,3‐synaxial interaction between the halogen and the hydrogen atoms in α‐position to an oxygen atom.
Acide mercapto‐3 pyridine carboxylique‐2
Authors: Dereppe J. H. , Schanck A. , Declercq J. P. , Germain G. , van Meerssche M. 
Published: September 2010

AbstractC6H5NO2S. Monoclinic, P21, Unit Cell: a=10.502, b=7.120, c=4.317 Å, β=96,16°, Z=2. Structure solved by direct methods shows quite planar molecules with internal S — H hydrogen bond.
Application of the floating spherical gaussian orbital (F.S.G.O.) model to the determination of photoelectron spectra of alkanes
Authors: André J. M. , Lambert‐Gérard M. E. , Lamotte C. H. 
Published: September 2010

AbstractThe application of the Floating Spherical Gaussian Orbital (FSGO) method to the determination of molecular photoelectron spectra of alkanes is described. Despite of its computational simplicity, the method is proved to give results in surprisingly good agreement with experiment.
Application of hollow cathode excitation coupled to vidicon detection to the simultaneous multielement determination of toxic elements in airborne dust.‐ A Unique sampling‐analysis procedure for lead and cadmium ‐
Authors: Broekaert J. A. C. 
Published: September 2010

AbstractA unique method for the simultaneous determination of lead and cadmium in airborne dust samples is described. Samples are collected by drawing air through porous cup graphite electrodes and analysed by excitation in a demountable hollow cathode lamp (H.C.L.) coupled to a vidicon detector. Detection limits for lead and cadmium are determined. Some analytical results for field collected samples are communicated.
Chemical studies of marine invertebrates. XXV1. Flexibilene, an unprecedented fifteen‐membered ring diterpene hydrocarbon from the soft coral Sinularia flexibilis (Coelenterata, Octocorallia, Alcyonacea)
Authors: Hérin M. , Colin M. , Tursch B. 
Published: September 2010

AbstractFlexibilene is a novel monocyclic diterpene hydrocarbon isolated from the soft coral Sinularia flexibilis. Spectroscopic analyses established its structure as 1,1',5,9,13‐pentamethyl‐Δ2,5,9,13‐cyclopentadecatetraene (II). Flexibilene is the first 15‐membered ring diterpene to be found in nature.
Stevens rearrangement and Hofmann elimination reactions of quaternary hexahydroindolium salts
Authors: Madsen J.Ø. , Lawesson S.‐O. 
Published: September 2010

AbstractTreatment of N,N‐dialkylhexahydroindolium salts, 1, with t‐BuOK leads to 4,5,6,7‐tetrahydroindoles, 7, 8, and 11, via competitive Stevens rearrangement and Hofmann elimination reactions.
Synthèse de Dérivés de Benzoxazepines. II. 5‐Aryl‐2,3,4,5‐Tetrahydrobenzo[f] 1,4‐Oxazepines
Authors: Waefelaer A. D. , Pecher J. , Dubois A. , Poultier P. 
Published: September 2010

AbstractSeveral new 5‐aryl‐2,3,4,5‐tetrahydrobenzo[f]1,4‐oxazepine derivatives (1 to 18) were prepared by reduction of the 2,3‐dihydro compounds. Adams platinium was a suitable catalyst for hydrogenation. With other catalysts, reduction of a nitro group or debenzylation may occur before the alteration of the imine function of the heterocycle. NaBH4 was suitable only in a few cases.
Une Méthode de Dérivation Directe des Équations Hartree‐Fock Non‐Restreinte
Authors: Smeyers Y. G. , Brucea A. M. 
Published: September 2010

AbstractOn présente une méthode d'obtention directe des équations Hartree‐Fock non‐restreinte (UHF), basée sur la minimisation de l'expression de l'énergie moyenne, sans recourir à la technique habituelle des multiplicateurs de La‐grange. La méthode fournit une expression pour les dits “multiplicateurs de Lagrange”, expression qui permet d'envisager d'autres procédés que 1'habituel pour résoudre les équations UHF.
Pulse Polarographic Determination of Trinitroglycerin in Explosives
Authors: Steeman E. 
Published: September 2010

AbstractThe application of pulse polarography for the qualitative and quantitative detection of the major constituent compound trinitroglycerin (TNG) and minor compounds such as trinitrotoluene (TNT), dinitrotoluene (DNT), diethylphtalate and 2‐nitrodiphenylamine in explosives has been described. Results are reproducible within 0.5 % in absolute value and 2.3 % relatively. Most of the results agree with the specifications of the manufacturer. Deviations may occur due to the interference of decomposition products or the presence of interfering minor compounds. A modification of a colorimetric method for the determination of TNG is also described.
Utilisation de la Résine de “Merrifield” en Synthèse Organique. I. Mono et Dialkylation de Dérivés D'Acides Amines
Authors: Szabo L. , Coppens E. , Clauder O. , Pecher J. 
Published: September 2010

AbstractThe primary amino group of two amino acids bound to the Merrifield resin was alkylated and the substrate was subsequently transesterified in acid or alkaline medium. Either an alkylamino ester or a dialkylamino ester was obtained in high yield according to the selected experimental conditions, the control of which is straightforward. The results are discussed in considering the controversy concerning the rigidity of the swollen polymeric matrix.
Synthesis of an Optically Active Triorganostannyl Ketone
Authors: Gielen Marcel , Simon Serge 
Published: September 2010

AbstractRacemic p‐(cyclohexylmethyl‐l‐naphthylstannyl) acetophenone (I) is transformed into its menthydrazone which is, after four recrystallizations, reconverted to optically active (I), [α]20°436 +0.25° ± 0.05°. Several methods have been used to determine the optical purity of optically active (I) without success.
Volatile Air Oxidation Products of Hop Bitter Acids
Authors: Blot J. M. , Verzele M. 
Published: September 2010

AbstractAir oxidation of hop bitter acids produces complex mixtures of volatile products, containing appreciable amounts of 2‐methyl‐3‐buten‐2‐ol (10 of table 1) and the lactone 5,5‐dimethyl‐(5H)‐2‐furanone (37 of table 1). Both have been identified in beer and have been attributed hoppy flavour. Separation and synthesis of these materials prove they have however no hoppy aroma characteristics.Air oxidation of humulone produces C9 hydrocarbons (8 and 11 of table 1). These have been reported in hop essential oil and were then thought to be “abnormal” terpenes. Other bitter acids do not give these hydrocarbons.
Nucleophilic Substitution Reactions of Brominated Dimethyl Alkylidene Malonates
Authors: Verhé R. , De Kimpe N. , De Buyck L. , Courtheyn D. , Schamp N. 
Published: September 2010

AbstractReaction of dimethyl 2‐bromo‐2‐methylpropylidene malonate with various nucleophiles mainly afforded dimethyl cyclopropane 1,1‐dicarboxylates while treatment with amines gave substitution products.
Voies Nouvelles en Synthèse de Prostaglandins (1)
Authors: Crabbé P. , Barreiro E. , Sook Choi H. , Cruz A. , Deprès J. P. , Gagnaire G. , Greene A. E. , Meana M. C. , Padilla A. , Williams L. 
Published: September 2010

AbstractThe preparation of novel prostaglandin analogues from PGA2, isolated from marine corals, is outlined.The synthesis of prostaglandins that contain a cyclobutane instead of the cyclopentane ring is described.In addition, a detailed account of the total synthesis of prostaglandins by the tropolone route is given.
Glycyl Methylene Chemical Shift Non‐Equivalence in Small Peptides. Diasteriomers of Leu‐Gly‐Phe
Authors: Anteunis Marc J. , Becu Christian , Lala Anil K. , Verhegge Georges , Narayan‐Lala Krishma 
Published: September 2010

AbstractMain possibilities for the origin of glycyl methylene chemical shift non‐equivalence in Gly‐containing small peptides are reviewed together with new data obtained at 300 and 360 MHz 1H‐nmr spectroscopy. An unexpected behaviour, both in glycyl methylene chemical shift non‐equivalence as in the similarity of mean shift values of these protons in the diasteriomeric tripeptides Leu‐Gly‐Phe rules out the electric field gradient contributions being of major importance. Changes in conformational features, both of the back‐bone as of the side chain rotation in function of pH are revealed, as follows from a study of coupling constants.
Solution Conformation of Lysocellin‐Na +; More Than a Simple Structural Analog of Lasalocid‐Na+
Authors: Anteunis Marc J. O. 
Published: September 2010

AbstractAlthough the covalent structure of Lysocellin (1) differs from Lasalocid (2) at both ends of the molecule, nevertheless the atomic coordinates are such that common ligands [0θ ‐1, OH‐5, C=0‐6 and OH‐10 in 1] lie in a square planar arrangement around the trapped central metal cation. Water of crystallization was present and may serve as an additional ligand. The complete structural architecture of 1 in solution has been unraveled by 2H‐nmr spectroscopy and allows a precise description (Figure 4) and comparison with 2 as previously reported2. A hydrophilic zone at one side of the flat molecule, which could be more or less accessible for polar interactions, is formed by 0‐2, OH‐3, 0‐7, OH‐8 and OH‐10. The outside periphery is screened by a crown consisting predominently of alkyl side chains attached to the back‐bone.
Hétérocycles Organiques De L'Arsenic:V Synthése, Structure Et Stéréochimie D'Arsatranes Tetracoordinés
Authors: Maroni P. , Holeman M. , Wolf J. G. 
Published: September 2010

AbstractA series of compounds (Ia to Id) derived from diethanolamines and bis(N,N dimethylamino) methyl arsane were synthetised. The coordinative bond N→ As in these molecules makes them “arsatranes”. The physicochemical results all suggest a trigonal bipyramid structure with nitrogen in the apex position. A stereochemical study of two of these compounds (Ic and Id) was carried out with static and dynamic NMR.
Preparation and Structure of Predione (1,2,3,4,5a,6,7,8,9,10a‐Decahydro‐4a, 9a‐Epoxidibenzo‐|1,4|‐Dioxin‐5a, 10a‐Diol)
Authors: Tavernier D. , Benijts F. , Verzele M. 
Published: September 2010

AbstractA large scale (2 mole) preparation of the title compound by nitric acid oxidation of cyclohexanol is described (47% yield). In chloroform, an equilibrium is established between predione and a tricyclic compound, shown to be cis‐3a, 4, 5, 6, 7, 7a‐hexahydro‐spiro|1,3‐benzodioxole‐2, 1′‐cyclohexane|−2′‐keto, −3a, 7a‐diol (4). The stereochemistry of predione is discussed.
Observation De Fragmentations De Seconde Région Libre De Champ D'Un Spectromètre De Masse à Géometrie Inversée Lors Du Balayage De La Tension D'Accélération
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , De Meyer C. 
Published: September 2010

AbstractIn a reversed geometry mass spectrometer first field free region fragmentations are usually detected by scanning the accelerating voltage. In some favourable instances, artifacts corresponding to second field free region processes are observed; the influence of a collision gas on their relative intensities is discussed.
Synthesis and X‐Ray Analysis of a New Representative of the Class of 3,4‐Diaza‐Trithiapentalenes
Authors: Stelander B. , Viehe H. G. , van Meerssche M. , Germain G. , Declercq J. P. 
Published: September 2010

AbstractA new synthesis of 1, 3, 5‐trichloro‐2, 4‐diazapentamethinium chloride (5) results from condensation of two equivalents of phosgene iminium salt (1) and cyanamide. The same product is also obtained from three equivalents of (1) and urea. Thiolysis of (5) leads to 2, 5‐bis(dimethylamino)‐3,4 diaza‐trithiapentalene (7).
A Comparative Oxidation Study of Some Thiane Derivatives.
Authors: van Acker Lucien , Anteunis Marc J. O. 
Published: September 2010

AbstractThree thianes substituted with a cis‐α', γ'‐diMe holding group and with in the ß‐ringposition of sulfur a C‐, O‐ and S‐atom respectively have been oxidized with a variety of oxidants and the isomeric distributions of the resulting mono‐sulfoxides have been analyzed by gaschromatography. The stereochemistry of these oxidations appears to be sensitive to steric constraints from ring substituents and to the electronic features of the substrate molecules.
Enamine Chemistry XVI Reactions Between Enamines and Chloral
Authors: Nolde C. , Lawesson S. ‐O. 
Published: September 2010

AbstractEnamines, derived from cyclic ketones, react with chloral stereo‐selectively to give high yields of only one of the possible isomers. The reaction between the same enamines and two moles of chloral leads to formation of 1:2‐adducts (mixture of isomers) having a 1,3‐dioxane structure. Factors controlling the steric course of these reactions are discussed.
Transformation Hydrothermale De Gels Appartenant Aux Systèmes MgO‐SiO2 ‐H2O‐F ET MgO‐Al2O3–SiO2‐H2O‐F
Authors: De Vynck I. 
Published: September 2010

AbstractThe influence of different fluoride concentrations on the cristallisation of MgO‐SiO2‐H2O and MgO‐Al2O3‐SiO2‐H2O gels, under hydrothermal conditions was studied.The fluoride changes the proportion Mg/Si available for reaction and has in that way a marked influence on the cristallisation of the gel observed after a definite hydrothermal treatment.
Studies in Oxadiazoles: Part VII. Synthesis And Fungicidal Activity of Some 2‐Sulfanilamido‐I,3,4‐Oxadiazoles and Their N4‐(o‐Carboxy‐Benzoyl)/Carboxyethylcarbonyl Derivatives
Authors: Singh H. , Yadav L. D. S. 
Published: September 2010

AbstractSome 2‐amino‐5‐aryl‐I,3,4‐oxadiazoles have been condensed with acetylsulfanilyl chloride, and 2‐(N4‐acetylsulfanilamido)‐5‐aryl‐I,3,4‐oxadiazoles thus obtained have been hydrolysed to provide the corresponding 2‐sulfanilamido‐I,3,4‐oxadiazoles. The latter have been condensed with phthalic and succinic anhydrides to yield 2‐[N4‐(o‐carboxybenzoyl])‐ and 2‐[N4‐(carboxyethylcarbonyl) sulfanilamido]‐I,3,4‐oxadiazoles, respectively. Three of these compounds were found to possess significant fungicidal activity against A. niger and A. flavus.
Comparaison Des Valeurs Du Potentiel Normal Du Couple Cu(II)/Cu(I) Dans Les Chlorures Alcalins Fondus, Obtenus Par Spectrophotométrie D'Absorption Et Par Polarographie
Authors: Mbuyi M. B. , Duyckaerts G. 
Published: September 2010

AbstractThe standard oxidation potentials of Cu(II)/Cu(I) in three alkali chloride melts at 450°C have been determined by absorption spectrophotometry and by pulse polarography; the values obtained are discussed and compared with those found in the literature.
Pulse Polarographic Determination of Europium in Minerals
Authors: Steeman E. , Temmerman E. , Verbeek F. 
Published: September 2010

AbstractDifferential pulse polarography was used for the quantitative determination of europium in minerals and oxides of lanthanides. The reduction of europium (III) to the divalent state shows suitable polarographic characteristics in several supporting electrolytes, for which differences in sensitivity have been tabulated. Procedures have been described for the direct determination of europium (III) in lanthanide‐oxides down to 0.2 ppm using 0.5 g samples. Europium was also determined in the mineral bastnaesite after a previous separation of the lanthanides by oxalate precipitation.
Coefficient De Diffusion De Cu(I) Déterminé Par Différentes Méthodes Dans Les Chlorures Alcalins Fondus a 450°C
Authors: Mbuyi M. B. , Duyckaerts G. 
Published: September 2010

AbstractThe interdiffusion coefficient of Cu(I) in three melts, LiCl‐KCl (58–42% mol.) LiCl‐CsCl (55–45% mol.), LiCl‐KCl (70–30% mol.) at 450°C for the two first and 457%dGC for the last one has been measured by different electrochemical methods: chronopotentiometry, cyclic voltammetry, pulse polarography and chronoamperometry, Chronopotentiometry gives systematically lower values for the diffusion coefficient. No significant influence of the nature of the solvent on the diffusion coefficient was observed.
Complexes of Tertiary Thioamides: Part III: Complexes of Dimethyl‐Thioacetamide with Co(II), Pd(II), Zn(II), Cd(II) and Hg(II)
Authors: Aarts A. J. , Desseyn H. O. , Herman M. A. 
Published: September 2010

AbstractComplexes of dimethyl‐thioacetamide (DMTA or L) with Co(II), Pd(II), Zn(II), Cd(II) and Hq(II) have been prepared and investigated by conductivity measurements, and by electronic, infrared and Raman spectroscopy. mL2Cl2 (M=Co, Zn, Hg), ML2I2 (M=Co, Zn, Cd, Hg) and [ML4] (ClO4)2 (M=Co, Zn, Cd) complexes are shown to be tetrahedral. CdLcl2 is polymeric, but a definite structure could not be assigned. Pd(II) forms planar cis‐PdL2Cl2, trans‐PdL2I2 and [PdL4] (ClO4)2. DMTA acts in all cases as a monodentate sulphur donor ligand.
On the Classification of Pairwise Relations Between Isomeric Structures
Authors: Mislow Kurt 
Published: September 2010

AbstractThe conventional classification of pairwise relations between structures of equal atomic composition gives primacy to the notion of constitution. It is asserted that a complete and edge‐weighted molecular graph is a more faithful representation of bonding relationships than a constitutional graph. A scheme is proposed, rooted in geometric rather than topological qualities of the model, which is well attuned to the distinguishing characteristics of isomeric pairs, and in which pairwise relations are classified as isometric (homomers, enantiomers) and anisometric (diastereomers, constitutional isomers). This classification is extended to topic relationships.