bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunological Reactions Carried out at a Liquid‐Solid Interface
Authors: Rothen A. , Mathot C.
Published: December 2004

Des γ‐globulines humaines et des polysccharides de pneumocoques de types III et VIII («antigènes») adsorbés en couches minces de 5 à 30 Å d'épaisseur sur des plaques métallisées par du chrome, sont capables d'adsorber spécifiquement des couches d'anticorps pouvant aller jusqu'à plusieurs centaines d'Å d'épaisseur. Les vitesses d'adsorption d'anticorps homologues par les couches de globulines ou de polysaccharides déposées sur les plaques furent mesurées avec un ellipsomètre enregistreur. Avec des plaques non recouvertes préalablement d'antigène, les couches adsorbées après immersion des plaques dans l'antisérum étaient extrêmement minces, d'environ 12 Å, ce qui montre bien que les adsorptions observées en présence d'antigène ont un caractère spécifique. De très grandes différences dans les vitesses d'adsorption sont observées selon que les plaques sont respectivement sèches ou mouillées au moment de l'immersion. Les plaques mouillées adsorbent les anticorps plus rapidement et en une couche plus épaisse que les plaques sèches pourvu que la densité d'antigène présent sur la plaque soit suffisamment élevée. Cette condition était réalisée par l'emploi de solutions d'antigène de 10−3 g/ml pour revêtir les plaques d'une couche d'antigène. Cette différence dans la vitesse d'adsorption peut s'expliquer si l'on formule l'hypothèse qu'il y a coopération entre les molécules d'antigène lorsqu'elles sont suffisamment voisines, ce qui permet une interaction à grande distance favorisant la diffusion des molécules d'anticorps à travers le film d'eau adhérant à la plaque, au détriment des globulines non spécifiques du sérum.

Lorsqu'un faible courant électrique (300 μA) est utilisé pour l'adsorption des antigènes et des anticorps, de très faibles concentrations d'antigène descendant jusqu'à 10−14 g/ml et parfois jusqu'à 10−15 g/ml peuvent être décelées.

Ces resultats ne sont obtenus qu'avec des plaques révélant par diffraction d'électrons la présence de cristallites de chrome partiellement orientés, d'au moins 50 Å de diamètre, ce qui confirme l'hypothèse que des phénomènes de coopération entrent en jeu dans ces réactions immunologiques à une interphase liquide‐solide.
Optical Rotatory Dispersion and Circular Dichroism Part LXXV: Circular dichroism of some aryl‐amino acids [1]
Authors: Klyne W. , Scopes P. M. , Thomas R. N. , Dahn H.
Published: December 2004

CD. curves have been recorded for α‐aryl‐α‐amino acids, esters and amides related to α‐phenylglycine, α‐phenyl‐alanine and their N‐dimethyl derivatives, and for the corresponding α‐cyclohexyl‐α‐amino acids and esters. Compounds with the (S)‐configuration at the single asymmetric carbon atom give strong positive Cotton effects near 220 nm. The conformations of the acids are discussed and compared with those of other α‐amino acids.
14N‐kernresonanzspektroskopische Untersuchungen an o‐substituierten N‐Äthylpyridiniumkationen
Authors: Giger W. , Schauwecker P. , Simon W.
Published: December 2004

In a series of 17 o‐substituted N‐ethylpyridinium salts the pyridinium nitrogen‐14 chemical shifts were determined by heteronuclear double resonance. A shift range of about 30 ppm was observed. No shift correlation was obtained with total electron densities calculated by the Extended Hückel Theory. By comparison with carbon‐13 shifts in analogously substituted aromatic systems a similar substituent dependence of 14N and 13C shifts could be established.
Etude des composés d'addition d'acides de Lewis, XXXVII [1] composés d'addition de quelques quinones avec TiCl4, et relation entre les fréquences carbonyle et diverses grandeurs physicochimiques
Authors: Giallonardo R.
Published: December 2004

1:1 or 1:2 solid stoichiometric adducts of TiCl4 with anthraquinone‐1,4, anthraquinone‐1,2, naphtacenequinone‐5,12, pentacenequinone‐6,13 have been prepared. The very important lowering Δω(CO) of the respective IR. carbonyl frequencies, ranging from −160 to −100 cm−1, shows that the acceptor is linked by a dative bond to the carbonyl oxygen atom acting as donor. On the basis of calculations and various considerations, the reduction of the CO double bond character is confirmed. Linear relations are found to exist between the oxydo‐reduction or the polarographic reduction potential of the quinones, and their antisymetric ωa(CO) frequencies, the values of Δω, and the O → Ti vibrations, respectively.
Studies of Oriented Monolayers on Solid Surfaces by Ellipsometry
Authors: Steiger R.
Published: December 2004

Zusammenfassung. Anhand ellipsometrischer Messungen an orientierten Monoschichten von Cd‐Arachidat, Perylen, Tripalmitin und Cyaninen auf aufgedampftem Gold oder auf reinen Silberbromideinkristallen wird gezeigt, dass damit Dicke und optische Konstanten solcher Monoschichten sehr genau bestimmt sowie Rückschlüsse über deren Stabilität (Kristallisation, Assoziationsverhalten, Reorientierung usw.) gezogen werden können.

Das abnormale Verhalten des komplexen Refraktionsindexes der ersten paar Monoschichten lässt auf die Gegenwart von absorbierenden Bereichen an der Grenze zwischen Substrat und Schichtsystem schliessen.
Transketolase from Human Erythrocytes Purification and Properties
Authors: Heinrich Peter C. , Wiss Oswald
Published: December 2004

Human erythrocyte transketolase (sedoheptulose‐7‐phosphate: D‐glyceraldehyde‐3‐phosphate glycolaldehyde‐transferase) was purified 8200‐fold by adsorption onto hydroxylapatite, DEAE‐cellulose treatment, acetone fractionation, and chromatography on Sephadex G‐100. The purified transketolase could not be separated from glyceraldehyde‐3‐phosphate dehydrogenase, whereas the latter enzyme could be isolated in a pure state. Its homogeneity is suggested by sedimentation velocity, sedimentation equilibrium, and acrylamide electrophoresis. A molecular weight of 136000 was found. The physicochemical properties of glyceraldehyde‐3‐phosphate dehydrogenase and transketolase are very similar. A molecular weight of 136000 is suggested for transketolase, although gel filtration with Sephadex G‐100 gave only 104000 ± 10%. This discrepancy is a reflection of an interaction of transketolase with the gel filtration medium. The isoelectric point for transketolase as well as for glyceraldehyde‐3‐phosphate dehydrogenase, as determined by isoelectric focussing, was found to be around 8.5. The activity of the enzyme is close to the maximum for pH 7.5 to pH 8.6. Additions of thiamine pyrophosphate or other cofactors do not influence the activity. Several divalent cations were tested. Sulfate and phosphate inhibit transketolase approximately to 50% between 50 and 100 mM concentration. Thiamine was present in transketolase, as shown by a microbiological assay and by the thiochrome reaction. The activation energy for the formation of sedoheptulose‐7‐phosphate from xylulose‐5‐phosphate was estimated from rate measurements to be 11.2 kcal/mole in the temperature range from 5° to 55°.
Microcalorimetric Determination of ΔH0, ΔG0 and ΔS0 for the Interaction of the Carrier Antibiotics Nigericin and monensin with sodium and potassium ions
Authors: Lutz W. K. , Früh P. U. , Simon W.
Published: December 2004

The thermodynamic parameters ΔH0, ΔG0 and ΔS0 – and thereby the equilibrium constants – for the complexation of the carrier antibiotics nigericin and monensin with sodium and potassium ions in methanol at 25°C have been determined by microcalorimetry. The results are discussed in terms of the nature of the interaction between ligands and cations.
Tris‐hexafluoropropyl‐2‐ates de terres rares
Authors: Merbach A. , Carrard J.‐P.
Published: December 2004

Tris‐hexafluoro‐2‐propoxides of yttrium, lanthanum, neodymium and erbium have been prepared, by the ammonia method, directly from the hydrated rare earth chlorides, dehydrated in situ by trimethyl orthoformate. The compounds are not volatile.
α, β‐Epoxyketon → Alkinon‐Fragmentierung I: Synthese von exalton und rac ‐ muscon aus cyclododecanon über synthetische methoden, 3. Mitteilung
Authors: Felix Dorothee , Schreiber J. , Ohloff G. , Eschenmoser A.
Published: December 2004

Experimental details concerning some examples of the tosylhydrazone version of the α, β‐epoxyketone → alkynone fragmentation as well as a discussion of this process are given.
Elektrocyclischer Ringschluss als Nebenreaktion bei einer Wolff‐Kishner‐Reduktion. Über Steroide, 227. Mitteilung
Authors: Kaufmann H. , Wieland P. , Kalvoda J.
Published: December 2004

A side reaction occurring in the Wolff‐Kishner reduction of certain acetylenic aldehydes (as e.g. 2 or 10) is shown to be a synchronous thermal process. The mechanism of this reaction is discussed in terms of the rules of the conservation of orbital symmetry.
Acidity Constants of the Thienyl‐ and Phenyl‐Pyridines and Stability Constants of the Corresponding Copper (II) 1:1 Complexes
Authors: Sigel Helmut , Wynberg Hans , van Bergen T. J. , Kahmann Klaus
Published: December 2004

The acidity constants of the six thienyl‐ and the three phenyl‐pyridines, and the stability constants of the corresponding Cu2+ 1:1 complexes were determined in aqueous solution (I = 0.1, NaCIO4; 25°). The basicity of the pyridyl group is increased by a shift of a thienyl or phenyl group in the order 2 < 3 < 4 and the influence of the 2′‐thienyl group is greater than that of the 3′‐thienyl group. The stability of the Cu2+ 1:1 complexes formed with 3‐ and 4‐substituted pyridines is only dependent on their basicity, as is commonly observed for structurally related ligands and their complexes. Due to steric hindrance the complexes of the 2‐substituted derivatives are less stable by about 1.5 log units. There is no evidence that the aromatic bonded sulfur of 2‐(2′‐thienyl)‐pyridine participates in complex formation with Cu2+, in opposition to an earlier claim [1].
Formation and dissociation mechanism of amide complexes III. Water substitution as the rate limiting factor for the interconversion of Cu2+ complexes with neutral and deprotonated amide groups
Authors: Zuberbühler A. , Kaden Th.
Published: December 2004

The protonation and deprotonation rates of the coordinated amide group in the Cu2+ complexes with Nα‐(2‐pyridyl‐methyl)‐glycinamide (I) and Nα‐(2‐pyridyl‐methyl)‐glycineethylamide (II) have been studied by stopped flow techniques. It is shown that the rate determining step of the formation of the complex with the deprotonated amide group is given by the rate of water dissociation from Cu2+. Weaker bases than OH− or stronger acids than water can react by a different path, in which the proton transfer and/or the rotation from the O‐co‐ordinated into the N‐co‐ordinated form and vice versa is rate determining.
Über die Indolalkaloide von Pleiocarpa talbotii Wernham. 145. Mitteilung über Alkaloide
Authors: Naranjo J. , Pinar M. , Hesse M. , Schmid H.
Published: December 2004

Besides talbotine (1) three new indole alkaloids, talpinine (2), talcarpine (3) and 16‐epi‐affinine (4) were isolated from the stem bark of Pleiocarpa talbotii Wernham. The structure of 2 was deduced by chemical degradation and by analyses of the spectra of the alkaloid and its derivatives. One of these derivatives is identical with talcarpine (3).

The structures 2 and 3 are similar to that of macroline (14), a splitting product of the bisindole alkaloid villalstonine from Alstonia species. 16‐epi‐Affinine (4) was chemically correlated with the known alkaloid vobasine (19).

Talpinine (2) and 16‐epi‐affinine (4) were also isolated from the root bark of Pleiocarpa talbotii.
Catalytic deoxygenation of organic compounds by carbon monoxide: III. The reaction under pressure of aromatic nitro compounds in the presence of o‐phthalaldehyde
Authors: Iqbal Abul F. M.
Published: December 2004

The reaction of o‐phthalaldehyde with several aromatic nitro compounds in the presence of carbon monoxide and catalytic quantities of hexarhodium‐hexadecacarbonyl eventuated in the formation of the corresponding N‐substituted isoindolinone as the major product. A reaction mechanism has been suggested incorporating deoxygenation of the nitro compound by carbon monoxide to a nitrene intermediate and the subsequent interception of the latter by o‐phthalaldehyde.
A Chiral Cystine Disulfide Group without Inherent Optical Activity in the Long‐Wavelength Region. (1H‐ and 13C‐NMR., UV., CD., and ORD. Studies with cyclo‐L‐cystine)
Authors: Donzel B. , Kamber B. , Wüthrich K. , Schwyzer R.
Published: December 2004

Konformation und Konfiguration von cyclo‐L‐Cystin wurden mit spektroskopischen Methoden untersucht. Nach 1H‐ und 13C‐NMR. besitzt die Molekel einen wannenförmigen Diketopiperazin‐Ring (CαH—NH‐Diederwinkel ⋍ 40°) und eine chirale Ausbildung der Disulfidbrücke. In Molekelmodellen mit diesen Spezifikationen beträgt der C‐S‐S‐C‐Diederwinkel φ ⋍ 90°. Im CD. war aber kein langwelliger Cotton‐Effekt zu beobachten, welcher auf eine inhärente optische Aktivität des asymmetrischen Disulfid‐Chromophors hinwiese. Dieses Verhalten stützt die Theorie von Linderberg & Michl [3 b], wonach bei Disulfiden mit φ = ±90°, infolge der Entartung der beiden Elektronenübergange niederer Energie und der irreduziblen Darstellung A bzw. B, die sonst getrennten Absorptionsbanden bei 250 nm zusammenfallen und ihre entgegengesetzten Rotationasstärken sich aufheben.

Den starken, negativen Cotton‐Effekt bei 228 nm (CD., in Äthanol) ordnen wir dem n,π*Übergang der Peptid‐Carbonylgruppe zu. Vorzeichen und Rotationsstärke (R = −45,4×10−40 erg · cm3) dieser Bande deuten wir als starke Indizien für das Vorliegen des cyclo‐L‐Cystins als P‐helikales Diastereomeres.
L‐Leucyl‐sarkosyl‐L‐phenylalanin, Synthese und Wirkung auf die Aminopeptidasen I und II von Bacillus stearothermophilus
Authors: Jost Rolf , Tun‐Kyi Aung , Stoll Erwin , Zuber Herbert
Published: December 2004

The synthesis of L‐leucyl‐sarcosyl‐L‐phenylalanine is described. This tripeptide resists hydrolysis by the aminopeptidases AP I and AP II from Bacillus stearothermophilus. The peptide is a reversible inhibitor of both enzymes. The inhibition constant for AP I is 5 × 10−3 mol/l and 1.5 × 10−3 mol/l for AP II.

In the hydrolysis of leucine p‐nitroanilide we observed noncompetitive inhibition by leucylsarcosyl‐phenylalanine with both enzymes.

With dipeptide substrates however, the inhibitory effect of leucyl‐sarcosyl‐phenylalanine was drastically reduced by saturating substrate concentrations.
Über eine neue Synthese von Uracilderivaten
Authors: Meindl H. , Ackermann H.
Published: December 2004

When N,N‐dialkylamide dimethylsulfate adducts are reacted with cyanoacetyl urea or carbethoxy acetyl urea, the corresponding dialkylamino alkylidene derivatives are formed which cyclize to substituted uracils in the presence of a strong base. When the adducts of cyclic amides are used, the lactam ring is opened simultaneously on cyclisation.
Synthesis of 9‐epi‐Quinine and 9‐epi‐Quinidine. Preliminary communication
Authors: Grethe G. , Gutzwiller J. , Lee H. L. , Uskoković M. R.
Published: December 2004

Die stereoselektive Synthese der beiden Cinchona‐Nebenalkaloide 9‐epiChinin (14) und 9‐epi‐Chinidin (15) wird beschrieben.
Synthesen mit Nitrilen. 33. Mitteilung. Phenylhydrazone des Dicyanmethylenindandions: Struktur und Farbe
Authors: Junek H. , Fischer‐Colbrie H. , Aigner H. , Braun A. M.
Published: December 2004

Die Darstellung von 2‐Dicyanmethylen‐indandion‐1,3‐monophenylhydrazonen wird beschrieben und die intensive, blaugrün bis violette Farbe der Verbindungen 2a–d diskutiert. Durch Vergleich mit dem gelb gefärbten 2‐Isopropyliden‐indandion‐1,3‐monophenylhydrazon (3c) wird der spezifische Einfluss der Dicyanmethylengruppe auf den Farbcharakter nachgewiesen. 2 a und b sind thermisch und lösungsmittelabhängig instabil und cyclisieren zu substituierten Indenopyridazinen 4a–b, deren chemische Reaktivität beschrieben wird.
Die Synthese von asymmetrisch substituierten o‐Hydroxyphenyl‐s‐triazinen
Authors: Brunetti H. , Lüthi C. E.
Published: December 2004

Mono‐ and bis‐(2‐hydroxyphenyl)‐s‐triazines 4, 14, 18, 22, 28, 29 can be prepared by (a) reaction of salicylic acid esters 2 with amidines 3; (b) reaction of 4H‐1, 3‐benzoxazin‐4‐ones 10 with amidines 3; and (c) Friedel‐Crafts‐reaction of chloro‐s‐triazines 26, 27 with resorcinol 24.

In case (b) the path of reaction is determined by the character of substituent R4 in 10. Scope and limitations of these reactions and accessibility of starting materials are discussed.
Synthèse d'une série de spiropyrannes benzothiazoliniques photochromes substitués en position 3
Authors: Samat André , Guglielmetti Robert , Metzger Jacques
Published: December 2004

La synthèse de spiropyrannes photochromes substitués en position 3 montre que la méthode de cyclisation classique est limitée dans certains cas, notamment pour les composés multifonctionnels ou lorsque les anhydrobases intermeAdiaires sont peu réactives; elle constitue en mêmo temps une généralisation de la synthèse en série benzothiazolinique. Les nouveaux substrats obtenus sont intéressants pour étudier l'influence des paramètres structuraux sur le photochro misme (cinétiques de décoloration thermique, sensibilité spectrale). Nous donnons enfin les caractéristiques spectroscopiques des composés synthétisés.
Notiz über die Kernresonanzspektren von trifluormethyl‐substituierten Naphthalinderivaten
Authors: Huber H. , Pascual C. , Wirz J.
Published: December 2004

The proton and fluorine NMR. spectra of 25 trifluoromethyl substituted naphthalene derivatives have been analysed. The proton chemical shifts of the trifluoromethyl naphthylamines and naphthols have been correlated with calculated π‐electron charge densities (PPP SCF).
Heterotricyclodecane VIII. (−)‐(1S, 3R, 6R, 8R)‐2, 7‐Dioxaisotwistan und (−)‐(1R, 3R, 6R, 8R)‐2, 7‐Dioxa‐twistan; Synthese und Bestimmung der absoluten Konfiguration
Authors: Ackermann P. , Tobler H. , Ganter C.
Published: December 2004

A synthesis and the determination of the absolute configuration of (−)‐(1S, 3R′ 6R, 8R)‐2, 7‐dioxa‐isotwistane (13) and (−)‐(1R, 3R, 6R, 8R)‐2, 7‐dioxa‐twistane (14) is described. The results for 14 are compared with those for carboeyclic (+)‐twistane (2) of known chirality.
Heterotricyclodecane IX. 2, 7‐Dioxa‐isotwistan, 2, 7‐Dioxatwistan und 2, 8‐Dioxa‐homotwistbrendan sowie Derivate
Authors: Wicker K. , Ackermann P. , Ganter C.
Published: December 2004

The synthesis of 2, 7‐dioxa‐isotwistane (10), 2, 7‐dioxa‐twistane (17), and 2, 8‐dioxa‐homotwistbrendane (36) and several of their derivatives is described starting from endo‐2‐hydroxy‐9‐oxabicyclo[3.3.1]non‐6‐ene (1).

The 10O(7)‐isotwistane iodide 7 and the corresponding tosylate 15 as well as the 10O(2)‐iodide 9 were treated under reaction conditions suitable for molecular rearrangements involving oxonium ions g and i, respectively, by neighbouring group participation leading to 2, 7‐dioxa‐twistanes and 2, 8‐dioxa‐homotwistbrendanes, respectively.
Dárivás C‐glycosyliques. IX. Syntháse de spiro‐Δ2‐isoxazolines et de spiro‐Δ1‐pyrazolines à partir du dásoxy‐3‐di‐O‐isopropylidène 1, 2: 5, 6‐máthylène‐3‐α‐D‐ribo‐hexofurannose. Communication práliminaire
Authors: Tronchet J. M. J. , Bourgeois J. M. , Suard Mlle Y.
Published: December 2004

Treatment of 3‐deoxy‐1, 2:5, 6‐di‐O‐isopropylidène‐3C‐méthylene‐α‐D‐ribo‐hexofuranose with aromatic nitrile oxides led to spiro‐Δ2‐isoxazolines, whereas a Δ1‐pyrazoline was obtained by reacting the same C‐methylenic sugar with diazomethane. Properties of these compounds, a new class of carbohydrates, and 5, 6‐di‐O‐acetyl derivatives thereof are described.
Dérivés C‐glycosyliques X. C‐Nucléosides oxadiazoliques inversés. Communication préliminaire
Authors: Tronchet J. M. J. , Moskalyk R. E.
Published: December 2004

The synthesis of «reversed» 1, 3, 4‐oxadiazolyl C‐nucleosides by treatment of alduronic chlorides with N‐benzoylamino‐triphenylphosphinimine or by oxidation of aldehydodialdose benzoylphenylhydrazones is described. One of these compounds is the first example of an «reversed» C‐amino‐nucleoside having a β‐heteroaryl‐ethylamino grouping, a structural unit whose introduction into a sugar molecule is interesting from a pharmacological standpoint.
Studies on the Primary Structure of Cow χ‐Casein.‐Structural Features of para‐χ‐Casein; N‐terminal sequence of χ‐caseinoglycopeptide studied with a sequencer
Authors: Jollès Jacqueline , Schoentgen Françoise , Alais Charles , Fiat Anne‐Marie , Jollès Pierre
Published: December 2004

Several long tryptic peptides obtained from reduced maleylated χ‐casein were sequenced: they belonged to the N‐ and C‐terminal (37 residues) moieties of para‐χ‐casein. Several tryptic peptides could then be joined by chymotryptic overlap peptides. 102 amino acid residues of para‐χ‐casein were thus placed into two long and four shorter sequences. Some structural results were established with a Sequencer which was also employed for a verification of the N‐terminal sequence of the χ‐caseinoglycopeptide; a previously described short glycopeptide was found again and was reinvestigated.
Bemerkungen zur Überführung von Resibufogenin in Bufalin. Über Krötengifte, 41. Mitteilung
Authors: Hauser Emil , Linde Hort H. A. , Spengel Sigrid
Published: December 2004

Bei der Reduktion von Resibufogenin 1 mit LiAlH4 bei tiefer Temperatur entsteht nicht wie von Kondo [11], Pettit [7], [8] und Sondheimer [5] beschrieben Bufalin 2 sondern das Hemiacetal 7.
Antibiotic X‐5108. II. Structure of goldinono‐1, 4‐lactone‐3, 7‐hemiketal, a degradation product of the antibiotic. Preliminary communication
Authors: Maehr Hubert , Blount John F. , Evans Ralph H. , Leach Michael , Westley John W. , Williams Thomas H. , Stempel Arthur , Büchi George
Published: December 2004

Antibioticum X‐5108 ist ein Naturprodukt mit neuartiger Struktur. Behandlung des Antibioticums mit Essigsäure führte zu einem kristallinen Abbauprodukt, das als 3(S)‐Äthyl‐3, 3a, 5(S), 6, 7, 7 a(R)‐hexahydro‐3a(R), 7(R)‐dihydroxy‐6, 6‐dimethyl‐5‐[1(cis), 3(trans)‐pentadienyl]‐2H‐furo[3, 2‐b]pyran‐2‐on (5) identifiziert wurde.
Konfigurationen und Konformationen von zwei 2,4,6,8‐Tetrabrom‐cyclooctan‐1, 5‐dionen
Authors: Heller Jürg E. , Dreiding André S.
Published: December 2004

The two isomeric tetrabromides, α‐isomer mp. 198° and β‐isomer mp. 226° described in [1], are identified as cis, cis, trans‐2, 4, 6, 8‐tetrabromo‐cyclooctane‐1, 5‐dione (2) and cis, trans, cis‐2, 4, 6, 8‐tetrabromo‐cyclooctane‐1, 5‐dione (3) by an analysis of their NMR.‐spectra which also allows a derivation of their preferred conformations. Both exist in solution as boat‐chair conformers, the geometries of which correlate well with the IR.‐ and UV.‐spectra.
Über die stereoisomeren α‐Phenyläthylamide der Biphenyl‐2,2′,6,6′‐tetracarbonsäure, Molekeln der Punktsymmetrie D2, S4, C2 und C1
Authors: Helmchen Günter , Haas Georges , Prelog Vladimir
Published: December 2004

All four possible diastereomeric α‐phenylethylamides of biphenyl‐2,2′, 6,6′‐tetra‐carboxylic acid (point symmetries D2, S4, C2 and C1) have been prepared and their properties investigated. Both enantiomers of the C2‐diastereomer have been synthetized along stereospecific routes which determine their absolute configurations.

Specification of molecular chirality and pseudoasymmetry of compounds with axial chirality in two and three dimensional space is discussed.
Zur Kenntnis von Rifamycin‐S.‐Reaktionen des Ansaringes. Modifikationen von Antibiotica, 8. Mitteilung [1]
Authors: Kump Wilhelm , Bickel Hans
Published: December 2004

The reactivity of rifamycin‐S with respect to acids, bases, and oxydizing or reducing agents has been studied. A number of compounds resulting from these experiments as well as derivatives of rifamycin‐S resulting from acylation and ketalisation reactions are described.
Über den Verlauf der Umsetzung von Steroid‐3,5‐dienaminen mit Formaldehyd
Authors: Schneider Fernand , Boller Arthur , Müller Marcel , Müller Peter , Fürst Andor
Published: December 2004

Reaction of steroidal 3,5‐dienamines (including 9β,10α‐ and 19‐nor‐compounds) with formaldehyde gave 6‐hydroxymethyl derivatives as major products. The latter compounds are valuable intermediates for the preparation of 6‐methyl‐3‐keto‐Δ4,6‐steroids.
Photochromie von Dimethylthiathiophthen und N‐Analoǵa von Thiathiophthenen
Authors: Calzaferri Gion , Gleiter Rolf , Gygax Reudi , Knauer Karl‐Heinz , Schmidt Erika , Behrinǵer Hans
Published: December 2004

Irradiation of N‐analogs of thiathiophthenes and dimethylthiathiophthene yield a transient which reverts thermally to the starting product. Kinetic measurements for this thermal reaction yield Ea values in the range of 9–14 kcal/mol and ΔS≠ values between – 10 and – 30 e.u. The structure of the transient is discussed based on these data, its electronic and infrared spectrum.
Notiz betreffend ladunsinduzierte Umlagerung von Allyl‐aryläthern mit Trifluoressiǵsäure
Authors: Widmer Ulrich , Hansen Hans‐Jürǵen , Schmid Hans
Published: December 2004

The rearrangement of allylarylethers (allylphenylether, crotyl‐4‐methylphenylether) in trifluoracetic acid to the corresponding 2‐allylphenols according to Svanholm & Parker [1] is shown to be of the charge‐induced [3s, 3s]‐type [3]. Because of the subsequent formation of cyclic ethers and other sideproducts, yields are low.
The Structure of Vincarodine
Authors: Neuss Norbert , Boaz Harold E. , Occolowitz John L. , Wenkert Ernest , Schell F. M. , Potier Pierre , Kan Christiane , Plat M. M. , Plat M.
Published: December 2004

The structure of vincarodine has been determined to be 1 by an investigation of its IR.‐, UV.‐, 1H‐ and 13C‐NMR.‐ and mass spectra. A 13C‐NMR. analysis has been performed on the bases vincamine (2), epivincine (9), 14, 15‐dehydrovincine (7) and its 16‐epimer (8).
Anil‐Synthese 9. Mitteilung. Über die Darstellung von in 4′‐Stellung heterocyclisch substituierten 4‐(2H‐Arenotriazol‐2‐yl)‐stilbenen
Authors: Siegrist A. E.
Published: December 2004

Durch Umsetzung von Schiff'schen Basen aus 4‐(2H‐Arenotriazol‐2‐yl)‐benzaldehyden und p‐Chloranilin mit p‐tolyl‐substituierten Heterocyclen aromatischen Charakters mit mindestens einem Ring‐Stickstoffatom können in Dimethylformamid in Gegenwart von Kaliumhydroxid die entsprechenden, in 4′‐Stellung heterocyclisch substituierten 4‐(2H‐Arenotriazol‐2‐yl)‐stilbene dargestellt werden («Anil‐Synthese»).
Metall‐π‐Komplexe des 2, 5‐Diphenyl‐1‐silacyclopentadiens
Authors: Fink Walter
Published: December 2004

The preparation of 2.5‐diphenyl‐1‐silacyclopentadienes and their reaction with iron carbonyls and π‐cyclopentadienyl‐dicarbonylcobalt yielding metal‐π‐silole complexes is described. Mass spectral data indicate the existence of an ‘aromatic’ silacyclopentadienyl species.
The Molecular and Crystal Structure of ψ‐Retroprogesterone
Authors: Weber H. P. , Galantay E.
Published: December 2004

The crystal structure of synthetic, racemic ψ‐retroprogesterone (9α‐methyl‐19‐nor‐progesterone) has been determined by X‐ray analysis and refined to R = 0.050. The analysis was carried out to establish the relative configuration at positions 9, 10 and 17 in connection with the biological activity of the compound.
Sur la composition de l'arôme de Thé noir IV
Authors: Cazenave Paul , Horman Ian , Mueggler‐Chavan Françoise , Viani Rinantonio
Published: December 2004

17 substances were shown to be present in the aroma of black tea. This brings the total number of substances now identified to 187. Many of these new aromatic constituents are present only in traces. Nevertheless they possess an appreciable olfactive intensity whose flowery and/or fruity characteristics are found in many perfumed black teas such as: Kenya, Darjeeling, Ceylan, China and Oolong.

The components were identified by GC/MS. and their presence in the aroma verified by GC.
Steroide und Sexualhormone. 251.Mitteilung [1]. Synthetische Versuche in der Limoninreihe I. Die Darstellung von C(19)‐oxygenierten 4,4‐Dimethyl‐5α‐bzw.‐5β‐steroiden
Authors: Schlatter Hans‐Rudolf , Lüthy Christoph , Graf Walter
Published: December 2004

Starting from 19‐hydroxytestosteroneacetate (1) a high yield preparation of 3‐oxo‐4,4‐dimethyl‐19‐hydroxy‐5α‐steroids (e.g. 7, 9, 13 and 33) is described.
Oxydation ausgewählter δ,ϵ‐ und ϵ,ξ‐ungesättigter Alkohole mit Blei(IV)‐acetat
Authors: Zink Markus Peter , Ehrenfreund Josef , Wolf Hans Richard
Published: December 2004

The lead tetraacetate (LTA) oxidation of dihydro‐γ‐jonol (2) gives the new bicyclic ether 4 in high yield. On the other hand, LTA oxidation of the alcohols 8, 14, 20, results in the formation of complex mixtures of oxidation products, from which the spiro compounds 10, 16, 22, the bicyclic ethers 11, 12, 17, 18, 23, and the carbonyl compounds 13, 19 have been isolated.
The Conjugative Interaction between π‐Orbitals and Cyclobutane‐Orbitals in Spiro[3.4]octa‐5,7‐diene and Spiro[3.4]octene‐5
Authors: Bischof Peter , Gleiter Rolf , De Meijere Armin , Meyer Lüder‐Ulrich
Published: December 2004

The photoelectron spectra of spiro[3.4]octane (1), spiro[3.4]octene‐5 (2), spiro[3.4]‐octa‐5,7‐diene (3), spiro[4.4]nonene‐2 (4) and spiro[4.4]nona‐2,4‐diene (5) have been recorded. The first bands of these spectra are correlated with orbitals which are π‐orbitals, Walsh orbitals resp. linear combinations of both. Our assignment is based on a qualitative ZDO‐model, it is in satisfactory agreement with the results of extended Hückel calculations. The interaction found in 2 and 3 is of similar magnitude as the one in 4 and 5 and considerably less than that in homofulvene and fulvene.
Zur Identifikation potentieller Metabolite von Cannabis‐Inhaltstoffen: Kernresonanz‐ und massenspektroskopische Untersuchungen an seitenkettenhydroxylierten Cannabinoiden
Authors: Binder Michael , Agurell Stig , Leander Kurt , Lindgren Jan‐Erik
Published: December 2004

The 100‐MHz‐NMR‐spectra of 11 side chain hydroxylated derivatives of cannabidiol (1), Δ6‐tetrahydrocannabinol (2) and cannabinol (3) were analysed for signals specific for the position of hydroxyl groups. The mass spectra of these compounds and their trimethylsilyl ethers were investigated at ionisation voltages between 70 and 10 eV. The mass spectra of the non‐silylated compounds showed no similarities independent on the basic type of cannabinoid but in the case of their trimethylsilyl ethers it was possible to derive fragmentations specific for the site of hydroxylation. These data are presented as a general method for the identification of small quantities of side chain hydroxylated in vitro and in vivo metabolites of cannabinoids.
The Electronic Spectra of Unsubstituted Mono‐ to Pentaacetylene in the Gas Phase and in Solution in the Range 1100 to 4000 Å
Authors: Kloster‐Jensen Else , Haink Hans‐Jochen , Christen Heinz
Published: December 2004

The electronic spectra of the title compounds I (n), n = 1 to 5, were recorded under standard conditions for quantitative comparison. Spectra of I(1) to I(4) in the gas phase and of I(2) to I(5) in nonpolar solutions are presented in a computer plotted form, and wave length maxima and intensities are listed. Tentative assignments of the medium‐intensity, first transition (A band) and the ultrahigh‐intensity, second transition (B band) are given. Finally, spectra of I(2) to I(5) recorded at − 150° are presented and discussed (A band). The syntheses of I(3) to I(5) are given in detail.
Photoaddition of Oxa‐enones to 2‐Chlorodifluoromethyl‐3‐chloro‐3,3‐difluoro‐propene
Authors: Margaretha Paul
Published: December 2004

Electronic effects determine the regiospecificity in the photoaddition of oxa‐enones to olefins.
Tetrahalo‐anti‐bis‐homoduroquinones by addition of dihalocarbenes to duroquinone
Authors: Chapleo Christopher B. , Dahl Charles E. , Dreiding André S. , Grieb Rita , Niggli Alfred
Published: December 2004

Doppelte Anlagerungen von Dichlorcarben und von Dibromcarben an Durochinon (1) ergaben 4,4,8,8‐Tetrachlor‐(3) und 4,4,8,8‐Tetrabrom‐1,3,5,7‐tetramethyl‐anti‐tricyclo[5.1.0.03,5]octan‐2,6‐dion (4) (= Tetrachlor‐ und Tetrabrom‐anti‐bis‐homodurochinon).

Die anti‐Konfiguration der beiden Diketone 3 und 4 wurde aus einfachen röntgenographischen Daten abgeleitet: Zwei Molekeln in der Elementarzelle und die Raumgruppe P21/n verlangen Zentrosymmetrie für die beiden Molekeln 3 und 4 im Kristallgitter, was die syn‐Konfiguration ausschliesst.
A chemical study of burley tobacco flavour (nicotiana tabacumL.) VI. Identification and Synthesis of Four Irregular Terpenoids Related to Solanone, Including a ‘Prenylsolanone’
Authors: Demole Edouard , Enggist Paul
Published: December 2004

Four novel constituents of Burley tobacco condensate have been identified as (E)‐5‐isopropyl‐7‐(2‐methyl‐tetrahydrofur‐2‐yl)‐hept‐6‐en‐2‐one (G), (E)‐5‐isopropyl‐7‐(2‐methyl‐tetrahydrofur‐2‐yl)‐hept‐6‐en‐2‐ol (H), (E)‐4‐methyl‐7‐isopropyl‐10‐oxo‐undec‐5‐en‐4‐olide (I), and (E, E)‐6,12‐dimethyl‐9‐isopropyltrideca‐5,10,12‐trien‐2‐one (J) or ‘prenylsolanone’. Compounds G, H, and I were synthesized from norsolanadione (1), compound J from solanone (A). These substances belong to a growing family of tobacco metabolites structurally related to solanone (A). Their possible formation from cembrene‐type precursors is briefly outlined.
Komplexe von Kupfer(I) mit Glyoxal‐bis‐N‐t.‐butylimin
Authors: Ayranci Halim , Daul Claude , Zobrist Markus , von Zelewsky Alex
Published: December 2004

Formation of strongly colored complexes of Cu+ with glyoxal‐bis‐(N‐t‐butylimin) (GLI) is observed in acetonitrile. Optical measurements reveal two complexes, Cu(GLI)+ (ṽmax = 26.0 kK, δ = 2800) and Cu(GLI) (ṽmax = 19.3 kK, ε = 8530). The equilibrium constants (0.1M tetraethylammoniumperchlorate) are logK1 = 3.9 and logK2 = 2.5. The equilibrium data are confirmed by potentiometric measurements with a copper electrode. In O‐donor solvents, only the 1:2 complex is observed. Cu(GLI)2CIO4 can be crystallized as a dark red solid which is stable towards atmospheric oxygen.
Umlagerungen der Phenylthiogruppe in Trimethylsilyl‐enoläthern von α,α‐dialkyl‐α‐phenylthio‐ketonen
Authors: Gerber Ulrich , Widmer Ulrich , Schmid Rudolf , Schmid Hans
Published: December 2004

Rearrangements of the Phenylthio Group of Trimethylsilyl‐enolethers of α,α‐Dialkylated α‐Phenylthio‐ketones

Trimethylsilyl‐enolethers of α,α‐dialkylated α‐phenylthio‐ketones undergo a photochemically induced 1,3‐phenylthio shift leading to isomeric enolethers in high yields. The rearrangement can also be carried out under thermal conditions, but the results are less satisfying.
Unimolecular Fragmentation of Energy Selected Allene Molecular Cations
Authors: Dannacher Josef , Vogt Jürgen
Published: December 2004

The unimolecular fragmentations of internal energy selected allene molecular ions (1+) have been investigated by photoelectron‐photoion coincidence spectroscopy. The energy dependence of the branching ratio between the two most important fragmentation channels is reported, together with values for the kinetic energy release during fragmentation. Loss of an hydrogen atom from 1+ is interpreted to proceed via two paths, yielding different isomeric forms of C3H with different kinetic energy release values.
Photolysis and Pyrolysis of N‐Methyl Isoindole
Authors: Rettig Wolfgang , Wirz Jakob
Published: December 2004

Near UV. irradiation of N‐methyl isoindole (1) in deaerated solution has yielded two constitutionally isomeric [π4s+π4s] dimers 3 and 4 (Scheme 2). No transient or stable photoisomers of 1 were detected. The photodimers were reconverted to 1 both by pyrolysis and photolysis. The photocleavage of dimer 3 proceeds (predominantly) by anonadiabatic pathway yielding 1 in its electronic ground state. Prolonged pyrolysis of 1 afforded 11H‐indeno [1,2‐c]‐isoquinoline (5) as a major product.
Analogues de la showdomycine à activité antitumorale
Authors: Tronchet Jean M. J. , Gentile Bernard
Published: December 2004

Antitumor showdomycin analogues

A series of 3‐glycosylidenesuccinimides (3) and 3‐glycosylidene‐1‐phenyl‐succinimides (5) have been prepared in good yields using a Wittig reaction. In each case, the preponderant, or even the exclusive, isomer formed was E. As expected from orbital considerations, the contribution to the conformational equilibrium of the rotamer whose HC (γ) and HC(δ) bonds were antiparallel was low. One of these succinimide derivatives 3a showed interesting anticancer activity, similar to that of the sugar enone C. These compounds probably act as somewhat selective alkylating agents.
1H‐NMR.‐spektroskopische Bestimmung der Enantiomerenreinheit von Allencarbonsäureestern mit optisch aktiven Europium‐Verschiebungsreagenzien
Authors: Lang Robert W. , Hansen Hans‐Jürgen
Published: December 2004

1H‐NMR. Spectroscopic Determination of Enantiomeric Purities of Allenic Esters Using Optically Active Europium Shift Reagents

The racemic allenic methyl esters 3‐‐7 and the racemic allenic diesters 8‐‐10 (cf. Scheme 2) in 1,1,2‐trichloro‐1,2,2‐trifluoroethane (TCFE) and CCl4 in the presence of optically active tris[3‐(heptafluorobutyryl)‐(+)‐camphorato]europium(III) (Eu(hfc)3) have induced unlike 1H‐NMR. shift differences (ΔΔδ) for the protons of the methoxycarbonyl groups of their enantiomers. In some allenic esters the shift reagent causes additional separation of resonance signals; thus, further substituents on the allenic framework may be differentiated in the racemic mixture. This finding provides a widely applicable method for the determination of absolute enantiomeric purities of allenic esters and their corresponding acids. Accordingly we found for optically pure (+)‐(S)‐2‐methyl‐2,3‐pentadienoic acid ((+)‐(S)‐13; cf. Fig. 2) a calculated [α] value of + 73.3 ± 1.8°. Finally, the substituent effects on ΔΔδ‐values (cf. Table 1‐‐3) are discussed.
Gilmicolin and Mycorrhizinol, Two New Metabolites of Gilmaniella humicolaBARRON
Authors: Chexal Kuldip K. , Tamm Christoph , Clardy Jon , Hirotsu Ken
Published: December 2004

The structure of gilmicolin and mycorrhizinol, two new metabolites isolated from culture filtrates of Gilmaniella humicola BARRON, have been shown to be 3 and 15 respectively by spectral and chemical studies. The X‐ray analysis of gilmicolin (3) is also reported.
Stereoselektive Bildung von Oxaspiropentanen und Spiropentylketonen. Zur Stereochemie der nucleophilen Substitution am Cyclopropan
Authors: Seebach Dieter , Dammann Reinhard , Lindner Hans Jörg , Kitschke Brigitte
Published: December 2004

Stereoselective Formation of Oxaspiropentanes and of Spiropentyl Ketones. On the Stereochemistry of Nucleophilic Substitution at Cyclopropanes

In an intramolecular SN2‐type substitution with formation of the spiro[2.2]‐pentane skeleton, the highly strained transition state 2 with one three membered ring in an equatorial/equatorial and one in an apical/equatorial position of a pentacoordinated carbon atom ought to be ‐ at least formally ‐ involved. Yet, several examples of such processes are known. With the endo/exo isomeric bromohydrines 4 and 5 and bromoketones 13 and 14 this reaction is now shown to occur with clean inversion of configuration at the cyclopropane carbon atom. Unambiguous configurational assignments are made by X‐ray crystal structure determinations of the 7′exo‐bromo‐benzoate 6 (from the bromohydrine 4), of the endo‐sulfonate 12 (from oxaspiropentane 7, formed from 4), of the 7exo‐bromonorcarane 13, and of its cyclization product 15. ‐ A comparison of the qualitatively measured rates of epoxide ring formation from the closely related systems 18 and 20 proves the expected slower substitution at the cyclopropane carbon atom as compared to the open chain analogue.
Eine ungewöhnliche Chlorwasserstoff‐Abspaltung: syn‐Eliminierung aus einem sterisch behinderten, aber freidrehbaren Halogenkohlenwasserstoff
Authors: Schlosser Manfred , An Tran Dinh
Published: December 2004

An Unusual Dehydrochlorination: syn‐Elimination from a Sterically Hindered, but Free Rotating Halogenated Hydrocarbon

Depending on the solvent, the meso‐3, 4‐dichloro‐2,2,5,5‐tetramethylhexane undergoes base‐promoted dehydrochlorination in a syn‐ or anti‐periplanar manner, thus affording (Z)‐3‐chloro‐2,2,5,5‐tetramethyl‐3‐hexene and the thermodynamically less stable (E)‐isomer, respectively. Alcoholate aggregates of different size (presumably, dimers and trimers or tetramers) are alternatively involved in these stereochemically distinct conversions, at least when potassium t‐butoxide in t‐butyl alcohol or tetrahydrofuran serves as a base/solvent system.
Über Pterinchemie. 70. Mitteilung. Konformationsanalyse von 5, 10‐Methenyl‐(6 RS)‐5,6,7,8‐tetrahydro‐L‐folsäure,
Authors: Khalifa Esam , Bieri Jost H. , Viscontini Max
Published: December 2004

Conformational analysis of 5,10‐methenyl‐(6RS)‐5,6,7,8‐tetrahydro‐L‐folic acid

Da die Titelverbindung seit langer Zeit unter dem angegebenen Namen bekannt ist, wird dieser Name beibehalten; aufgrund der IUPAC‐Regel C‐83.1 scheint uns allerdings korrekter, wenn «methenyl» durch «methylenylium» ersetzt wird, wobei es jedem klar sein muss, dass es sich hier um den Namen einer Grenzformel handelt: die positive Ladung sitzt in Wirklichkeit auf einem oder auf dem anderen der benachbarten N‐Atome (Red.).

Conformational analysis of the diastereomeric 9,9‐dideuterio‐5,10‐methenyl‐(6RS)‐5,6,7,8‐tetrahydro‐L‐folic acids (IV) in the 100‐MHz‐1H‐NMR. spectrum shows a trans‐diaxial arrangement of HaC(6) (A‐part) and HaC(7) (X‐part) (JAM = 10.6 Hz) and a gauche arrangement of HaC(6) and HeC(7) (M‐part) (JAM = 4.2 Hz). Accordingly the tetrahydropyrazine ring in IV exists in the same manner as in tetrahydrofolic acid but with a more marked half chair conformation and with a pseudo equatorial position of the C(6), C(9) bond.

A similar analysis of the diastereomeric 7,7‐dideuterio‐5, 10‐methenyl‐(6RS)‐5,6,7,8‐tetrahydro‐L‐folic acids (VIII) in the 360‐MHz‐1H‐NMR. spectrum shows an almost identical situation with higher values of J between HaC(6) (A‐part) and HC(9β) (B‐part) on one side (J = 11.2) and between HaC(6) and HC(9α) (X‐part) on the other side (JAX = 9.2). This can be reached only when the imidazolinium ring of VIII is nearly planar (Fig. 3).
Hydrogen Generation by Visible Light Irradiation of Aqueous Solutions of Metal Complexes. An approach to the photochemical conversion and storage of solar energy
Authors: Kirch Michele , Lehn Jean‐Marie , Sauvage Jean‐Pierre
Published: December 2004

We describe a photochemical system for the generation of hydrogen by water reduction under visible light or sunlight irradiation of aqueous solutions containing the following components: a photosensitizer, the Ru (bipy) complex, for visible light absorption; a relay species, the Rh (bipy) complex, which mediates water reduction by intermediate storage of electrons via a reduced state; an electron donor, triethanolamine (TEOA) which provides the electrons for the reduction process and a redox catalyst, colloïdal platinum, which facilitates hydrogen formation. The conditions for efficient hydrogen production and the influence of the concentration of the components have been investigated; the metal complexes act as catalysts with high turnover numbers; excess bipyridine facilitates the reaction. The process contains two catalytic cycles: a ruthenium cycle and a rhodium cycle. The Ru cycle involves oxidative quenching of the *Ru(bipy) excited state by Rh(bipy) forming Ru(bipy) which is converted back to Ru(bipy) by oxidation of the electron donor TEOA, which is thus consumed. The Rh cycle comprises a complicated set of transformations of the initial Rh(bipy) complex. The reduced rhodium complex formed in the quenching process undergoes a series of transformations involving the Rh(bipy) complex and hydridorhodium‐bipyridine species, from which hydrogen is generated by reaction with the protons of water. In view of the storage of two electrons in the reduced rhodium species, the process is formally a dielectronic water reduction. The properties and eventual participation of [Rh(III)(bipy)2LL′]n+(L,L′ = H2O, OH−) species are investigated. It is concluded that at neutral pH in presence of excess bipyridine, the cycle involving regeneration of the Rh(bipy) complex is predominant. A number of experiments have been performed with modified systems. Hydrogen evolution is observed with other photosensitizers (like proflavin), other relay species (like Rh(dimethylbipy) or Co(II)‐bipyridine complexes), other donor species, or in absence of the platinum catalyst. It also occurs in absence of photosensitizer by sunlight of UV. irradiation of Rh(bipy) or by visible light irradiation of iridium (III)‐bibyridine complexes. These systems deserve further investigations. The present photochemical hydrogen generating system represents the reductive component of a complete water splitting process. Its role in solar energy conversion and in photochemical fuel production is discussed.
A Comparative 13C‐NMR. Study on Various Reduced Flavins
Authors: Van Schagen Cees G. , Müller Franz
Published: December 2004

Various two‐electron reduced flavin derivatives have been investigated by natural abundance 13C‐NMR. spectroscopy. Some selectively 13C‐enriched compounds were synthesized to ensure the assignment of some of the quaternary C‐atoms of the flavin molecule. Addition of two electrons to oxidized flavin leads to upfield shifts of all resonances except for those due to C(5a), C(9) and C(10′α). The largest upfield shift is observed for C(4a). Also some direct and two‐bond coupling constants are reported. Theoretical calculations by INDO show that a rather good correlation exists between the calculated π‐electron densities and the observed chemical shifts of the two‐electron reduced molecule. For the oxidized molecule, the correlation is less satisfactory. Most substitution effects are additive, but some deviations in some compounds are observed indicating structural differences between the compounds in question.

The chemical shifts are also discussed in terms of the chemical reactivity of the oxidized and reduced flavin molecule.
13‐C‐Chemical Shift/Charge Correlations in Unsaturated Systems as Obtained by Semiempirical MO‐Methods: A Reinvestigation
Authors: Baumann Harold , Olsen Henrik
Published: December 2004

The Spiesecke & Schneider relationship between charge and 13C‐chemical shifts has been widely used in recent years. In the present work a set of 20 organic compounds with a total of 50 different chemical shifts has been investigated with respect to the applicability of this relation. Attempted correlation between 13C‐shifts and charges indicated that the proportionality constant highly depends on the MO‐method used. In order to circumvent these problems paramagnetic shifts were computed using standard techniques. The effect of including a diamagnetic shift correction is discussed.
Photochemische Reaktionen 114. Mitteilung [1]. Zur Photochemie cyclischer Acetale vom 1,3‐Dioxa‐4,6‐cycloheptadien‐Typus
Authors: Murato Kazuo , Frei Bruno , Wolf Hans Richard , Jeger Oskar
Published: December 2004

Photochemistry of Cyclic Acetals of the 1,3‐Dioxa‐4,6‐cycloheptadiene Type

UV.‐irradiation (λ=254 nm) of 3 gives the isomers (E)‐5 (4%), (Z)‐5 (60%) and 6 (3%). On triplet sensitization (acetone; λ ≥ 280 nm) 3 is converted to (E)‐5 (3%), (Z)‐5 (7%) and 7 (9%). − The 1π,π*‐excitation (λ=254 nm) of 4 yields the isomers 2 (9%), 8 (10%), 9 (34%), 10 (20%) and 11 (3%). On thermolysis (200°) 4 gives 10 (87%) by a Claisen‐rearrangement.
Lipophilic Di‐ and Triamides as Ionophores for Alkaline Earth Metal Cations
Authors: Erne Daniel , Stojanac Nada , Ammann Daniel , Hofstetter Peter , Pretsch Ernö , Simon Wilhelm
Published: December 2004

Different electrically neutral lipophilic di‐ and triamides were prepared and their ion selectivity in membranes studied. In membranes the ionophore N, N′‐diheptyl‐N, N′‐dimethyl‐succinamide prefers Ca2+ over Mg2+ by a factor of 20 but rejects Na+ and K+ in respect to Mg2+ by a factor of 100 and 10, respectively. This selectivity suffices to perform useful intracellular Mg2+ activity studies.
Steroids and Sex Hormons. Part 263. [1]. On the Mechanism of the Reaction of 17‐Hydroxyimino‐steroids with Carbodiimide/Dimethylsulfoxide
Authors: Pfenninger Johannes , Graf Walter
Published: December 2004

Treatment of the (Z)‐isomers 6 and 7 of the four isomeric 16‐acetoxy‐17‐hydroxyimino‐steroids 6–9 with DCC/DMSO/CF3COOH (Moffat fragmentation of oximes) yielded the seco‐α‐acetoxy‐nitriles 10 and 11, respectively, while similar treatment of both (E)‐isomers 8 and 9 gave the formyl‐carbonitrile 14. The mechanism of these fragmentations is discussed. 13C‐NMR. data of oximes are presented which show the γ‐gauche effect being associated with σ (CH)‐bond polarization.