bluuebunny/crossref_metadata_2025_split huggingface dataset:
3‐Amino‐3‐desoxyverbindungen von Uzarigenin, Oleandrigenin, Gitoxigenin und Digoxigenin. Partialsynthetische Versuche in der Reihe der Herzgifte, 6. Mitt.
Authors: Hauser Emil , Boffo Ursula , Meister Lotte , Sawlewicz Ludwika , Linde Horst H. A. , Meyer Kuno 
Published: December 2004

AbstractEs werden die Partialsynthesen der 3‐Aminoverbindungen der im Titel genannten Cardenolide beschrieben.
Contribution à la phytochimie du genre Gentiana, VI. Etude des xanthones dans les feuilles de Gentiana bavarica L.
Authors: Hostettmann Kurt , Tabacchi Rafaël , Jacot‐Guillarmod André 
Published: December 2004

AbstractTen tetraoxygenated xanthones (1‐hydroxy‐3, 7, 8‐trimethoxyxanthone I; 1, 7‐dihydroxy‐3, 8‐dimethoxyxanthone II; 1, 7, 8‐trihydroxy‐3‐methoxyxanthone III; 1, 3, 7, 8‐tetrahydroxyxanthone IV; 3, 7, 8‐trimethoxyxanthone‐1‐O‐primeveroside V; 7‐hydroxy‐3, 8‐dimethoxyxanthone‐1‐O‐primeveroside VI; 1, 8‐dihydroxy‐3‐methoxyxanthone‐7‐O‐acetylrutinoside VII; 7, 8‐dihydroxy‐3‐methoxyxanthone‐1‐O‐primeveroside VIII; 3, 7, 8‐trihydroxyxanthone‐1‐O‐primeveroside IX; 3, 7, 8‐trihydroxyxanthone‐1‐O‐glucoside X) have been isolated from leaves of Gentiana bavarica L. by means of column chromatography on polyamid. Among these xanthones, VI, VII, VIII and IX were not encountered before in nature.
Dediazoniations of Arene Diazonium Ions in Homogenous Solution. Part IV: Change‐over from a heterolytic to a homolytic mechanism in 2,2,2‐trifluoroethanol pyridine mixtures
Authors: Burri Peter , Loewenschuss Hana , Zollinger Heinrich , Zwolinski Gene K. 
Published: December 2004

AbstractThere are only two dediazoniation products of benzenediazonium tetrafluoroborate in 2,2,2‐trifluoroethanol (TFE), namely phenyl 2,2,2‐trifluoroethyl ether (1) and fluorobenzene (2). The reaction kinetics are strictly first‐order with respect to the diazonium salt. The addition of increasing amounts of pyridine to the system results in a gradual decrease in the yields of 1 and 2 and an increase in the yields of the homolytically formed products, benzene (3), biphenyl (4), isomeric phenylpyridines (5) and diazo tar (6). The reaction kinetics show that the rate of dediazoniation of the benzene diazonium salt increases with increasing amounts of pyridine. The reaction with added pyridine is no longer first‐order with respect to the diazonium ion.The product analyses and the kinetic data are consistent with the view that in pure TFE this diazonium salt decomposes completely by a heterolytic mechanism. The addition of pyridine brings about a competitive homolytic mechanism which becomes increasingly dominant as the concentration of pyridine increases.
5‐(1‐Alkenyl)‐1, 3, 4‐oxadiazol‐2(3H)‐one
Authors: Rüfenacht Kurt 
Published: December 2004

Abstract3‐(2‐alkenoyl)‐thiocarbazic acid O‐methyl esters 1 are desulfurated by bromine and the unknown intermediates are transformed by alkali to 5‐(1‐alkenyl)‐1, 3, 4‐oxadiazol‐2(3H)‐ones (2). This type of oxadiazolone substitution is not realizable by the common ring closure of hydrazides with phosgene due to pyrazolidinone ring closure of unsaturated acids with hydrazine.
Der Einfluss von Substituenten in Stellung 4 auf das n‐Ionisationspotential des Chinuclidins
Authors: Bieri Gerhard , Heilbronner Edgar 
Published: December 2004

AbstractThe vertical ‘lone‐pair’ ionization potentials Iv(n) of fifteen 4‐substituted quinuclidines, of aza‐adamantane and of aza‐twistane have been determined by photoelectron spectroscopy. It is shown that the dependence of Iv(n) on the nature of the substituent S can be rationalized in terms of the contribution to the local potential at the ionization site (i.e. the nitrogen centre) by the dipole of S. Both the solution pK's and Iv(n) correlate with classical substituent parameters (e. g. σ* or F) and with each other. However, no conclusions can be drawn from such regressions concerning a close relationship between the electronic mechanisms responsible for the observed changes in pK or Iv(n).
Transposition bis‐homoallénylique: solvolyse de γ‐tosylates alléniques
Authors: Ragonnet Bernard , Santelli Maurice , Bertrand Marcel 
Published: December 2004

AbstractCyclisation (formation of derivatives of 2‐methylidene‐cyclopentanol or cyclohexanone) with inversion of configuration and retention of optical activity is observed during the solvolysis of secondary γ‐allenic tosylates.Steric factors rather than electronic ones control the participation of one of the double bonds in the allenic system. Kinetic results and product distribution are discussed.
Stoffwechselprodukte von Mikroorganismen. 130. Mitteilung. Synthese des δ‐N‐Hydroxy‐L‐arginins
Authors: Widmer Jörg , Keller‐Schierlein Walter 
Published: December 2004

AbstractA synthesis of the antibiotically active amino acid, δ‐N‐hydroxy‐L‐arginine, starting from L‐ornithine is described. In addition a new synthesis of δ‐N‐hydroxy‐L‐ornithine, an important building stone of many sideramines, is given.
Effect of Pressure in the Gamma Radiolysis of Cyclohexane in the Vapor Phase
Authors: Milon Hubert , Gäumann T. 
Published: December 2004

AbstractThe vapor phase γ‐radiolysis of cyclohexane has been investigated as a function of pressure, from 100 to 0.5 Torr, in vessels of different dimensions. With decreasing pressure, the yield of hydrogen and substituted cyclohexanes is decreased and the formation of molecules having less than six carbon atoms is enhanced. The curves of yield vs. pressure have a sigmoïd shape from which we define a transition pressure depending only on the dimensions of the vessels, the variation of the yield of a given product being the same for all the vessels. We propose and discuss a simple model of competition between the neutralization of the ions in the volume and their diffusion to the surface where they are neutralized. From the slope of the curve of the inverse of the transition pressure vs. the square of the characteristic diffusion length, we evaluate a maximum life‐time of 68 ms for the ions, using a calculated value of the cyclohexane ions diffusion coefficient.
Isomerisierungen und Umlagerungen in Bicyclischen Systemen via cyclopropan‐carbaldehyd‐enamine
Authors: Rey Max , Dreiding André S. 
Published: December 2004

AbstractThe pyrrolidino‐aminal (4) of bicyclo[3.1.0]hex‐2‐ene‐6‐endo‐carbaldehyde (3) underwent a facile (80°), mildly acid catalyzed isomerization to the corresponding exo‐aminal (6), which was characterized by hydrolysis to bicyclo[3.1.0]hex‐2‐ene‐6‐exo‐carbaldehyde (7).At higher temperatures (140°), the two aminals 4 and 6 were converted smoothly to a 1:1 mixture of syn‐ and anti‐4‐(pyrrolidino‐methylidene)‐bicyclo[3.1.0]hex‐2‐ene (syn‐ and anti‐7‐pyrrolidino‐homofulvene1) 8 and 9. The structures of 8 and 9 were derived from spectral data. This corrects a previous interpretation by Cook et al.The endo → exo‐aminal isomerization (4 → 6) is considered to occur via the enamine (5) of bicyclo[3.1.0]hex‐2‐ene‐6‐carbaldehyde (3 or 7), with which the aminals (4 and 6) are in equilibrium. The same enamine (5), a methylidene cyclopropane derivative, is thought to be the intermediate in the aminal (4 or 6) → amino‐homofulvene (8 and 9) conversion, which, therefore, belongs to the vinyl‐methylidene‐cyclopropane rearrangement type.A cationic mechanism for the endo → exo‐aminal isomerization is excluded by the discrepancy in this reaction of the pyrrolidino‐aminals (13 and 15) of 6‐exo‐methyl‐bicyclo[3.1.0]hex‐2‐ene‐6‐endo‐carbaldehyde (12) and of bicyclo[3.1.0]hexane‐6‐endo‐carbaldehyde (14). While the former aminal (13) is stable even under acid catalysis and at higher temperatures, the latter (15) isomerizes readily to the exo‐aminal 16.The three endo‐aldehydes 3, 12 and 14 were prepared by the alkali catalyzed rearrangement of the three chlorohydrins 7‐endo‐chloro‐bicyclo[3.2.0]hept‐2‐en‐6‐endo‐ol (20ac), 7‐endo‐chloro‐7‐exo‐methyl‐bicyclo[3.2.0]hept‐2‐en‐6‐endo‐ol (20ad) and 7‐endo‐chloro‐bicyclo[3.2.0]heptan‐6‐endo‐ol (20bc) according to the method of Brook.The configurations of the unsaturated endo‐aldehydes 3 and 12 followed from their equilibria with the corresponding 2‐oxa‐bicyclo[3.2.1]octa‐3,6‐diene systems (23) and those of the saturated aldehydes 14 and 17 from oxidations to the corresponding carboxylic acids. The endo‐ and exo‐ isomers of the aldehydes and aminals treated in this work were readily distinguished by certain highly characteristic NMR.‐signals.
Die Addition von Imidazolderivaten an DCCI; eine Nebenreaktion bei der Synthese von Histidinpeptiden
Authors: Rink Hans , Riniker Bernhard 
Published: December 2004

AbstractIn the synthesis of histidine peptides by means of the carbodiimide method the formation of Nim‐amidino‐histidine derivatives as secondary products has been observed. The reaction of imidazoles with DCCI leading to such compounds and their cleavage have been investigated. The significance of this side‐reaction in peptide synthesis is discussed.
Surface Chemistry of Polymers Physical Adsorption of Nitrogen, Argon, Sulfur Dioxide and Neopentane on Polyvinylidene Fluoride
Authors: Houriet Jean‐Philippe , Ghiste Patrick , Stoeckli Fritz 
Published: December 2004

AbstractThe adsorption of nitrogen, argon, sulfur dioxide and neopentane on polyvinylidene fluoride has been measured by static methods and by gas‐solid chromatography. The polymer has a homogeneous surface of low energy, which is not significantly affected by heating.
A Stereospecific Synthesis of (E, Z)‐α, β‐γ, δ‐Diunsaturated Aldehydes, Ketones, and Esters Using the Benary Reaction
Authors: Näf Ferdinand , Decorzant René 
Published: December 2004

AbstractThe reaction between (Z)‐1‐alkenyllithium and (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenals, (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenones or (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenoic esters yields mainly (E, Z)‐α, β‐γ, δ‐diunsaturated aldehydes, ketones, or esters and is therefore highly stereospecific.
Stereoselective Ring Closure of Methyl‐5‐hexenyl‐aluminium Systems
Authors: Stefani Annibale 
Published: December 2004

AbstractA remarkable intramolecular stereoselectivity was observed in the ring closure reactions of 1‐, 2‐, 3‐, and 4‐methyl‐5‐hexenyl‐aluminium systems. The possible relationship between this stereoselectivity and the relative thermodynamic stabilities of the conformers involved in the cyclization reactions, is discussed.
Photochemische Cycloadditionen von 3‐Phenyl‐2H‐azirinen an Carbonsäurechloride. 35. Mitteilung über Photoreaktionen
Authors: Schmid Ursula , Gilgen Paul , Heimgartner Heinz , Hansen Hans‐Jürgen , Schmid Hans 
Published: December 2004

AbstractIrradiation of 2, 3‐diphenyl‐2H‐azirine (1a) and 1‐azido‐1‐phenyl‐propene, the precursor of 2‐methyl‐3‐phenyl‐2H‐azirine (1b), in benzene, with a high pressure mercury lamp (pyrex filter) in the presence of acid chlorides yields the oxazoles 5a–d (Scheme 2). Photolysis of 2, 2‐dimethyl‐3‐phenyl‐2H‐azirine (1c) under the same conditions gives after methanolysis the 5‐methoxy‐2, 2‐dimethyl‐4‐phenyl‐3‐oxazolines 7a, b, d, while hydrolysis of the reaction mixture leads to the formation of the 1, 2‐diketones 8a, c, d (Scheme 4). The suggested reaction path for all these reactions is a 1, 3‐dipolar cycloaddition of the photochemically generated benzonitrilemethylides 2 to the carbonyl double bond of the acid chlorides to give the intermediates 4, followed by either elimination of hydrogen chloride or solvolysis (Schemes 2 and 4).Irradiation of 1c in the presence of acetic acid anhydride leads via the intermediate 9 to the 5‐hydroxy‐3‐oxazoline 10 and the 5‐methylidene‐3‐oxazoline 11 (Scheme 5).
Photochemische Cycloadditionen von 3‐Phenyl‐2H‐azirinen mit Triphenyl‐vinylphosphoniumbromid. 36. Mitteilung über Photoreaktionen
Authors: Gakis Nikolas , Heimgartner Heinz , Schmid Hans 
Published: December 2004

AbstractOn irradiation in acetonitrile 3‐phenyl‐2H‐azirines of type 1 react with triphenyl vinyl phosphonium bromide to form in approximative 50% yield 2H‐indoles of type 4 (Scheme 1). In analogy to other photochemical reactions with 2H‐azirines [2] [3] it is assumed that the photochemically generated dipoles 2 react with the triphenyl vinyl phosphonium salt (Scheme 1). The conversion of 1 to 4 represents a new synthesis for 2H‐pyrroles.
Radical Anion of Azuleno[5.6.7‐cd]phenalene, a Failure of the Simple HMO Model
Authors: Gerson Fabian , Jachimowicz Joanna , Jutz Christian 
Published: December 2004

AbstractHyperfine proton coupling constants are reported for the radical anions of azuleno‐[5.6.7‐cd]phenalene (I), 6‐phenylazulene (II) and the corresponding 1,3‐dideuterio‐derivatives (I‐d2 and II‐d2). The singly occupied orbitals of both I⊖ and II⊖ are found to be symmetric with respect to the mirror plane perpendicular to the plane of the molecule. In the case of I, surprisingly, such an orbital corresponds not to the first, but to the second lowest antibonding HMO. A correlation diagram for the relevant orbitals of I and II indicates that the correct energy order in the HMO model of I can be achieved by a decrease in the absolute value of the parameter βμν for the bonds 4a–5, 6–6a, 9a–10 and 11–11a.
Stoffwechselprodukte von Mikroorganismen. 139. Mitteilung. Synthesen in der Sideramin‐Reihe: Rhodotorulasäure und Dimerumsäure
Authors: Widmer Jörg , Keller‐Schierlein Walter 
Published: December 2004

Abstractt‐Butyl (E)‐O‐acetyl‐Δ2‐anhydromevalonate could be prepared. by a Reformatsky reaction of 4‐acetoxybutan‐2‐one and t‐butyl bromoacetate. Condensation of its activated derivatives with the diketopiperazine of N5‐hydroxy‐L‐ornithine led to di‐O‐acetyl dimerumic acid, which could be transformed, by ammonolysis, to dimerumic acid, identical with the natural compound. The corresponding acetohydroxamic acid, prepared by acetylation of the diketopiperazine, was identical with natural rhodotorulic acid.
Dielectric Properties of Apolar Micelle Solutions Containing Solubilized Water
Authors: Eicke Hans‐Freidrich , Shepherd John C. W. 
Published: December 2004

AbstractVarying amounts of water have been solubilized in a micelle solution of sodium di‐2‐pentyl–sulfoscuccinate in benzene and the complex permittivity has been observed in the range 200 KHz to 10 MHz. Part of a dielectric dispersion is seen, which extends to higher frequencies with a broad distribution of relaxation times. Due to association processes, the static dielectric increment is found to vary non‐linearly with hydrated micelle concentration and with the amount of solubilized water, whereas a linear variation with micelle concentration is found if no water is added. These effects are explained on the assumption that part of the solubilized water increases the dipole moment of the micelle.Additionally, at higher water concentrations, a sudden increase in the conductivity of the solution is observed, which is taken to indicate a conformational change of the solubilized micelle.
Terpenoids Derived from Linalyl Oxide. Part 3. The isolation, structure, absolute configuration and synthesis of the davanafurans, nor‐sesquiterpenes isolated from Artemisia Pallens
Authors: Thomas Alan F. , Dubini Renée 
Published: December 2004

AbstractThe novel nor‐sesquiterpenoids, the davanafurans, have been isolated from the oil of Artemisia pallens, the principal component being the cis, threo‐isomer (1a). The absolute configuration of this isomer, and the relative stereochemistry of the other isomers, have been established by synthesis from linalool oxides of known configuration.
The Wall Effect on Hydrogen Formation in the Vapour‐Phase Radiolysis of c‐C6D12 and n‐C7D16
Authors: Fujisaki Noboru , Gäumann Tino 
Published: December 2004

AbstractVapour‐phase radiolysis of c‐C6D12 and n‐C7D16 leads to a relatively large HD yield, up to ∼ 20% of the total hydrogen, which cannot be accounted for by incomplete deuteration of c‐C6D12 and n‐C7D16. In order to elucidate the mechanism of the HD formation, we have examined the effect of additives and of physical conditions on the HD yield. By coating the vessel with a layer of Aquadag the HD yield is greatly decreased without appreciable variation of the total hydrogen yield. The HD yield from nontreated vessels also decreases remarkably with increasing total dose; it is increased upon the addition of traces of water; and is less affected by small amounts of c‐C6H12. The addition of SF6 selectively reduces the HD yield. These experimental results lead us to conclude that inert hydrocarbon ions react by proton transfer with water desorbed from the vessel wall to give hydronium ions which yield HD on subsequent neutralization.
1,2,3,4,5‐Pentamethyl‐5‐acetyl‐cyclopentadien‐1,3, ein ungewöhnliches Keton
Authors: Burger Ulrich , Delay Arlette , Mazenod François 
Published: December 2004

AbstractIt has been shown that the reaction of the title ketone with phosphorous pentachloride leads to regiospecific chlorine transfer to the diene moiety of the molecule, leaving the carbonyl function intact. Attempted acetalization with ethylene glycol did not give the dioxolane but rather 1,2,3,4,5‐pentamethylcyclopenta‐1, 3‐diene in quantitative yield. An independent synthesis of this hydrocarbon, previously available only by lengthy multistep synthesis, has also been described. The only normal carbonyl reaction of the permethyl‐acetyl‐cyclopentadiene observed was the reduction by metal hydrides.
FIR.‐Spektren von Übergangsmetallkomplexen mit orthogonalem Ligandensystem. I. Halogeno‐Kupfer(II)‐Komplexe methylsubstituierter Pyridine
Authors: Stieger Hans‐Rudolf , Ludwig Werner 
Published: December 2004

AbstractFar‐infrared spectra (400–40 cm−1) have been studied for orthogonal systems CuL2X2 (L = pyridine, mono‐, di‐, tri‐methylsubstituted pyridine and X = Cl, Br). Assignements are suggested for the four bands of the molecular vibrations which form a stable region within the spectra of the complex series. Relations between number and position of bands and structural data are discussed.
Energy Sequence of the Lowest Antibonding Orbitals in Symmetrical Didehydro[n]annulenes with n = 4N+2
Authors: Gerson Fabian , Jachimowicz Joanna , Nakagawa Masazumi , Iyoda Masahiko 
Published: December 2004

AbstractA model of a perturbed n‐membered perimeter (n = 4N + 2) is used to interpret the ESR.‐data for the radical anions of symmetrical tetra‐t‐butyl‐didehydro[n]annulenes with n = 14, 18, 22 and 26 (N = 3, 4, 5 and 6). The singly occupied orbital of such radical anions correlates with one of the doubly degenerate, lowest antibonding perimeter MO's which have been classified as symmetric (ΨS) or antisymmetric (ΨA) with respect to the mirror plane passing through two opposite centres and perpendicular to the plane of the perimeter. The relevant MO is ΨS for n = 14 (N = 3) and 22 (N = 5), but ΨA for N = 18 (N = 4) and 26 (N = 6), in accordance with the prediction of the model. It has been shown that the introduction of two symmetrically placed triple bonds into a (4N + 2)‐membered perimeter should stabilize ΨS and destabilize ΨA when N is odd, whereas the reverse should hold when N is even.
The Gas‐Solid Interface Calculations of Adsorption Potentials in Slot‐Like Pores of Molecular Dimensions
Authors: Stoeckli Fritz 
Published: December 2004

AbstractTwo theoretical models are presented for the calculation of adsorption potentials in slot‐like pores of molecular dimensions, with respect to the adsorption by a single flat surface. The cases of continuous and layer‐like solids are considered, with interatomic pair‐potentials of the 6:12 type, and for pore widths ranging from two to four times the equilibrium distance of adsorption. Both models give good results for the adsorption of simple molecules by microporous carbons and graphitized carbon blacks.
Synthesen der Nonactinsäure
Authors: Gerlach Hans , Wetter Hansjürg 
Published: December 2004

AbstractTwo stereoselective syntheses of nonactic acid I, the building block of the macrotetrolide antibiotic nonactin are described. The characteristic cis‐configuration of the 2,5‐substituents on the tetrahydrofuran ring of I is obtained in the first synthesis by catalytic hydrogenation of the furan derivative X. This key intermediate possesses the carbon skeleton and correct distribution of oxygen functions for conversin into nonactic acid. It is synthesized by an electrophilic substitution of 2‐acetonylfuran (VI) with the N‐cyclohexyl‐N‐propenyl nitrosonium ion (V) generated from the corresponding α‐chloronitrone (VII) and silver fluoroborate, followed by hydrolysis and oxidation of the aldehyde group.The second synthesis starts with a diol already having the correct configuration of the side chain that contains the hydroxyl group. For this purpose threo‐1‐octen‐5,7‐diol (XV) is synthesized from acetylacetone in two steps. Oxidative cleavage of the terminal double bond of this threo‐diol yields an aldehyde which is converted by a Wittig reaction, with the carbanion, obtained from diethyl α‐methoxycarbonylethyl phosphonate, into the open chain intermediate, 2‐methyl‐6,8‐dihydroxy‐2‐nonenoic acid methylester (XVIII). Base‐catalyzed cyclisation of this α,β‐unsaturated dihydroxy ester yields the methyl ester of nonactic acid (I) as the main product.
Electron Transfer Spectra of the Hexachloro‐ and Hexabromoniobate(V) and Tantalate(V) Anions
Authors: Valloton Mario , Merbach André E. 
Published: December 2004

AbstractThe electron transfer spectra of the hexachloro‐ and hexabromoniobate (V), and‐tantalate(V) anions are investigated with particular care to avoid hydrolysis products. New interpretations are given, and the optical electronegativities χ of Nb(V) and Ta(V) are recalculated. The difference between both χ values is 0.2, in better agreement with the differences observed for metals of the second and third transition series.
Interaction of ophidian L‐amino acid oxidase with its substrates and inhibitors: Role of molecular geometry and electron distribution. Communication 6 on ophidian L‐amino acid oxidases
Authors: Zeller E. Albert , Clauss Lorraine M. , Ohlsson John T. 
Published: December 2004

AbstractMolecular activities, determined polarographically for the degradation of phenylalanine and 21 meta‐ and para‐substituted derivatives by crystalline L‐amino acid oxidase, yielded a linear Hammett plot of positive slope. However, the presence of large moieties in the para‐position led to negative deviations which were linearly correlated with van der Waals' radius of the substituent. This suggested that the large substituents cause the substrate molecules to be displaced from their normal (eutopic, productive) position at the active site, resulting in lower velocities. In analogous experiments with competitive inhibitors (ring‐substituted benzoic and phenylacetic acids), the logarithm of K1 was found to be a linear function of Hansch's hydrophobic constant π. Lines of different slope characterized the meta‐ and para‐derivatives, suggesting that the nature of the substituent affects the strength of hydrophobic binding, while the locus determines the orientation of the inhibitor on the active site. An analysis of the data reported here and in the literature for meta‐ and para‐compounds supports the idea that the geometry of the ring‐substituted substrate affects the orientation of the molecule on the active site, which may in turn determine which step of the reaction sequence becomes rate‐limiting.