bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative Auswertung von Gas‐Chromatogrammen partiell getrennter Stoffgemisch
Authors: Bosshard Ch. , Piringer O. , Gäumann T.
Published: December 2004

A simple method is described for the qualitative and quantitative analysis of gas chromatograms with considerably overlapping peaks, based on the assumption of known retention indices and peak shapes. Its application to mixtures of deuteriated hydrocarbons is indicated.

The extent to which the results are reproducible is shown to be about the same as that of high‐resolution gas chromatography or mass spectrometry.
11, 12‐Dihydro‐ 12‐hydroxy‐tribenzo[c,g,m]‐1,2,5,6,9,12‐hexa‐azacyclotetradecine; a Neutral Homoaromatic [14]Annulene Macrocyclic Aza Compounds, I
Authors: Skrabal P. , Zollinger H.
Published: December 2004

The structure of the title compound 2 is supported by spectra and analysis; homoaromaticity is deduced from its NMR. and electronic spectra.
The Electronic Spectrum of Tricyclo[3.3.0.0.2,6]octa‐3,7‐diene
Authors: Gleiter R. , Kobayashi T.
Published: December 2004

The unusual electronic spectrum of the title compound is shown to be due to the strong interaction between the π‐orbitals of the double bonds and the Walsh‐orbitals of the fourmembered ring.
Über Pterinchemie. 36. Mitteilung [1]. Herstellung von 6‐Aminomethyl‐6,7‐dimethyl‐5,6,7,8‐tetrahydropterin und Mechanismus seiner Oxydation unter physiologischen Bedingungen
Authors: Viscontini M. , Cogoli‐Greuter M.
Published: December 2004

Zur Herstellung von 6‐Aminomethyl‐6,7‐dimethyl‐5,6,7,8‐tetrahydropterin wurde das durch Blausäureaddition an 6,7‐Dimethyl‐7,8‐dihydropterin entstandene 6‐Cyano‐6,7‐dimethyl‐5,6,7,8‐tetrahydropterin acetyliert, reduziert und anschliessend desacetyliert. Wie das 6‐Aminomethyl‐6‐methyl‐5,6,7,8‐tetrahydropterin bildet das 6,7‐Dimethylhomologe während seiner Oxydation mit Luftsauerstoff unter physiologischen Bedingungen kein Parachinoiddihydropterin. Nach der vollständigen Oxydation wurde neben dem erwarteten 6,7‐Dimethylpterin auch 6‐Methylpterin isoliert. Der Mechanismus der 6‐Methylpterin‐Bildung wird diskutiert.
Darstellung und spektroskopische Untersuchungen von Kupferkomplexen mit verschiedenen Mikrostrukturen, III Komplexe mit dreifach koordiniertem Kupfer (II)
Authors: Ludwig W. , Textor M.
Published: December 2004

Die Existenz monomerer Teilchen CuCl3− und CuBr3− wird bestätigt. Ihre Elektronenspektren ohne Störung durch Fremdteilchen werden mitgeteilt und auf der Basis der Molekelorbital‐Theorie interpretiert. Ausserdem wird gezeigt, dass alle theoretisch möglichen Komplexe mit gemischtem Chloro‐Bromo‐Ligandensystem existieren, und dass dreifach koordiniertes CuII weicher ist als Kupfer mit den normalen Koordinationszahlen 4 bzw. 6. In nichtkoordinierenden Lösungsmitteln sind die Teilchen planar und assoziieren sich bei den erreichbaren Konzentrationen nicht merklich. Der erste erlaubte Elektronentransfer‐Übergang ist von kleiner Halbwertsbreite und wird bei den Mischkomplexen nicht aufgespalten, sondern ändert seine Energie symbath mit der mittleren optischen Ligand‐Elektronegativität bei sukzessivem Austausch der einzelnen Halogenidliganden. In den Elektronentransferzuständen liegt demnach in Übereinstimmung mit der Erwartung aus der Molekelorbital‐Theorie eine kollektive Oxydation der Liganden vor. Relativistische Effekte (Spin‐Bahn‐Kopplung) haben selbst beim Tribromokomplex keinen auffallenden Einfluss auf das Elektronentransferspektrum. Schliesslich werden die Elektronenspektren der CuX3−‐ mit denjenigen der CuX42−‐Komplexe verglichen.
Protonenresonanzspektren von aromatischen N‐Oxiden Berechnung der chemischen Verschiebungen, verursacht durch die Feldeffekte der NO‐gruppe
Authors: Hamm P. , Philipsborn W. V.
Published: December 2004

The proton NMR. spectra of a series of aromatic amines, their N‐oxides and the corresponding protonated species are analysed. The results for different protons are expressed in terms of differential chemical shifts of the N‐oxide with respect to the corresponding amine or to the hydrocarbon. These data are compared with calculated shielding values obtained according to the theories of McConnell & Buckingham using published data for the magnetic susceptibilities and electric dipoles of the functional groups. The major part of the shielding by the N‐oxide group originates from the electric dipole. If one considers resonance structures for the aromatic N‐oxides the single bond structure and the double bond structure for the NO bond are of approximately equal importance.
Oxydative Demethylierung durch Leberhomogenat von Ratten nach Vitamin E‐Mangel und nach Tocopherolgaben
Authors: Bernhard K. , Markstein R. , Zimmerli W.
Published: December 2004

Zusammenfassung. Das sauerstoffabhängige demethylierende Enzymsystem aus Leberhomogenat oder Lebermikrosomenpräparaten wird durch α‐Tocopherol nicht beeinflusst. Eine deutliche, aber langsamer verlaufende Enzyminduktion nach Angewöhnung mit dem Substrat (N‐Methyl‐glutethimid) ist indessen auch in durch Vitamin E‐Mangel geschädigten Zellen nachweisbar.
The Reaction of Methyl Tosylate with Halide Ions in Pyridine‐Dimethylformamide
Authors: Müller Paul , Siegfried Bernard
Published: December 2004

The reactivity of the lithium halides in 83.3% pyridine‐dimethylformamide changes from Cl− > Br− > I− to Br− > I− to Br− > I− > Cl− with increasing concentration of the salt from 0 to 0.35 M. This behaviour is explained by ion pairing which reduces the concentration of reactive free nucleophiles. Equilibrium constants K for ion pair dissociation and rate constants k2 for the reaction of the free nucleophiles were determined from the variation of the observed rate constant with the total halide concentration and from conductivity measurements.
Synthèse en phase solide de l'hormone de libération de l'hormone lutéotrophique (LH‐RH)
Authors: Rivaille Pierre , Robinson Arthur , Kamen Martin , Milhaud GÉRard
Published: December 2004

A rapid and convenient synthesis of LH‐RH using the benzylhydrylamine resine is described.
Über das Lipoxygenase‐«Lipoperoxidase»‐System in Cerealien: II. Charakterisierung des hydroperoxide‐abbauenden enzyms
Authors: Schreier P. , Heimann W.
Published: December 2004

Zusammenfassung. Durch an Hafer mit einem Ammoniumsulfatpräparat ausgeführten Untersuchungen wird bestätigt, dass am enzymatischen Linolsäurehydroperoxid (LHPO)‐Abbau eine Peroxidase beteiligt ist, welche die Bildung von Hydroxy‐cis‐trans‐dienfettsäuren aus LHPO katalysiert. Dabei fungieren die aus der H2O2‐Peroxidase‐Katalyse bekannten Verbindungen als Wasserstoffdonatoren. Durch Messungen mit p‐Phenylendiamin‐dihydrochlorid als Wasserstoffdonator werden die für das Enzym charakteristischen Eigenschaften ermittelt.
Neue β‐Lactam‐Antibiotika. Über die Darstellung der «7‐Aminocephalocillansäure». Modifikationen von Antibiotika, 4. Mitteilung [1]
Authors: Scartazzini R. , Peter H. , Bickel H. , Heusler K. , Woodward R. B.
Published: December 2004

‘7‐aminocephalocillanic acid’ 1, an intermediate for the preparation of new β‐lactam antibiotics was prepared by transforming the β‐lactam carbinol 2a to the phosphorane 9a through several steps. Oxydation of 9a with DMSO/Ac2O led directly to the cyclized ester 11a, which has been converted into 1 by known methods.
Neue β‐Lactam‐Antibiotika. Über die Darstellung von N‐Acylderivaten der 7‐Amino‐ceph‐3‐em‐4‐carbonsäure. Modifikationen von Antibiotica, 6. Mitteilung [1]
Authors: Scartazzini R. , Bickel H.
Published: December 2004

Oxydation of 2 with iodine followed by acylation leads to β‐lactamdisulfides of type 3. Compounds 3 can be transformed into alcohols 4 by reductive alkylation with ethylenoxide and zinc/acetic acid. Compounds 4 are used as starting materials for the synthesis of N‐acylderivatives 12 of 7‐amino‐ceph‐3‐em‐4‐carboxylic acid (D).
Heterotricyclodecane. VII. 2,7‐Dithia‐isotwistan und Derivate
Authors: Ganter C. , Wigger N.
Published: December 2004

The synthesis of 2,7‐dithia‐isotwistane (18) and several of its derivatives (13–17) was achieved starting from endo‐2‐chloro‐9‐thiabicyclo[3.3.1]non‐6‐ene (3) and using the bicyclic mercaptan 7 as a key intermediate.

The isotwistane halides 13 and 14 were treated under reaction conditions suitable for molecular rearrangements involving an epi‐sulfonium ion (a) by neighbouring group participation. However, only isotwistane derivatives were formed (13 → 16, 13 → 17, 14 → 16, 14 → 17) and no rearranged products with twistane structure could be isolated.
Über Pterinchemie. 40. Mitteilung [1]. Weiterer Beitrag zur Synthese des Biopterins
Authors: Viscontini M. , Provenzale R. , Frei W. F.
Published: December 2004

Eine neue Synthese des Biopterins ausgehend von L‐4‐Methyl‐erythrulose und 2,4,5‐Triamino‐6‐hydroxy‐pyrimidin wird beschrieben. Bei der Oxydation des intermediär gebildeten Tetrahydrobiopterins wird die Dihydroxypropyl‐Kette so leicht abgespalten, dass die Ausbeute an Biopterin auch bei dieser Synthese 15% nicht übersteigt. Eine mögliche Erklärung dieser Abspaltung wird vorgeschlagen.
On the Mechanism of Decarboxylation of Betanidine. A Contribution to the Interpretation of the Biosynthesis of Betalaines
Authors: Dunkelblum E. , Miller H. E. , Dreiding André S.
Published: December 2004

Bei der Biogenese des Betanins (2) aus Dopa (1) wird die Carboxylgruppe der Aminosäure in die Carboxylgruppe‐C(19) umgewandelt. Dieser Schluss beruht auf einem Deuterierungsversuch, bei dem gezeigt wird, dass die Monodecarboxylierung von Betanidin (3) zu einem Verlust von C(19) führt und dass dabei die Doppelbindung C(17)C(18) nach C(14)C(15) wandert. Wenn radioaktives Betanidin (3), erhalten aus Einbauexperimenten mit DL‐Dopa‐[1‐14C], in Äthanol decarboxyliert wird, erhält der danach isolierte Dimethylester 7 des Decarboxybetanidin (6)‐hydrochlorids nur noch 14% des 14C.

Bei der alkali‐katalysierten Äquilibrierung von Betanidin (3) ⇆ Isobetanidin (9) tritt im Gegensatz zur Decarboxylierung keine Wanderung der Doppelbindung ein.
The HCL‐Catalyzed Stereomutation of Cyclic Sulfoxides
Authors: Sagramora L. , Garbesi A. , Fava A.
Published: December 2004

The critical step in the HCl‐catalyzed stereomutation of sulfoxides is a nucleophilic substitution at the sulfur atom [7]. The rate of this reaction has been determined for cyclic sulfoxides as a function of ring size. The trend closely matches that long since established for substitution at alicyclic carbon [11], which confirms the similarity of the geometries of the transition states for substitution at carbon and at sulfur. The results are compared to those for the analogous silicon and phosphorous compounds, and the question of formation of pentacovalent intermediates for substitutions at sulfur is briefly discussed.
Die 1,3‐dipolare Cycloaddition von Acetylendicarbonsäure‐estern an 2‐Methyl‐4‐phenyl‐chinazolin‐3‐oxid
Authors: Stauss U. , Härter H. P. , Neuenschwander M. , Schindler O.
Published: December 2004

The 1,3‐dipolar addition of acetylenedicarboxylic esters (IX and X) to 2‐methyl‐4‐phenyl‐quinazoline 3‐oxide (VIII) in benzene/methanol and benzene/ethanol, respectively, gives the esters XI and XII of 3‐amino‐3‐phenyl‐2‐(2‐acetamidophenyl)‐acrylic acid as main products and the esters XIII and XIV of 2‐methyl‐4‐phenyl‐5H‐benzo[d][1,3]diazepin‐5‐carboxylic acid as by‐products. The constitutions of XI and XII are elucidated by acid hydrolysis to the 2‐phenylindole‐3‐carboxylic esters VI and VII, respectively, and by ozonolysis of XII to give benzamide and ethyl o‐acetamido‐mandelate (IV). The alkaline hydrolysis of XI or XII gives the enamine derivative XVIII, which is hydrolysed by acid to oxindole and benzoic acid. The structure elucidation of XIII and XIV is based on spectroscopic data together with thc formation of XV by alkaline hydrolysis. Mechanisms arc proposed for the reaction paths.
The π‐Orbital Energies of the Acenes
Authors: Clark Patricia A. , Brogli F. , Heilbronner E.
Published: December 2004

The ‘observed’ π‐orbital energies ϵv,j = −Iv,j derived from the vertical ionization potentials obtained by a photoelectron spectroscopic investigation of the acenes benzene A(1), naphthalene A(2), anthracene A(3), naphthacene A(4) and pentacene A(5) have been compared with π‐orbital energies calculated by three different approximations: (a) the standard Hückel HMO model; (b) a first‐order perturbation treatment, based on (a), that takes into account bond length changes which follow the ionization process; (c) a SCF π‐electron model of the type proposed by Pople and by Pariser & Parr. In agreement with previous experience it is found that model (b) yields the most satisfactory parametrization of the experimental data.
Decomposition of Aryldiazonium Ions in Homogenous Solutions Part II: Arylations with benzenediazonium ions and p‐nitrobenzenediazonium ions in dimethyl sulfoxide
Authors: Gloor B. , Kaul B. L. , Zollinger H.
Published: December 2004

When p‐nitrobenzenediazonium tetrafluoroborate is decomposed in the presence of dimethyl sulfoxide/benzene or dimethyl sulfoxide/nitrobenzene systems under nitrogen, the respective biphenyl derivatives are obtained in good yield. With benzenediazonium tetrafluoroborate in the same systems the yields are low. The influence of oxygen, iodine, iodobenzene and N, N‐diphenylhydroxylamine on the products of the reactions were determined. The by‐products, isomer distribution with nitrobenzene as a substrate, and the partial and total rate factors were also determined. From the above data it can be shown that the reaction with p‐nitrobenzenediazonium salt is a homolytic process and that with the unsubstituted benzenediazonium salt is essentially a heterolytic reaction. The problem of the mechanism of the radical forming steps (electron transfer or adduct formation) and the mechanistic relationship to other modes of arylation (aroylperoxide, classical two‐phase Gomberg‐Bachmann reaction, catalysis by transition metal ions, nitrite ions, etc. electron transfer properties of DMSO) are discussed.
The N1s ESCA Spectrum of Protonated 1,8‐Bis‐(Dimethylamino) Naphthalene (“proton sponge”)
Authors: Haselbach E. , Henriksson Anita , Jachimowicz F. , Wirz J.
Published: December 2004

The ESCA spectrum of protonated 1,8‐bis‐(dimethylamino) naphthalene (“proton sponge”) (I) has been recorded in the region of N1s binding energies. The results indicate that IH+ possesses an unsymmetrical NH…︁N hydrogen bridge.
Zur Reaktionsweise von Enaminen mit Cyclopropenonen IV. Einsatz von Ketenacetalen
Authors: Steinfels M. A. , Krapf H. W. , Riedl P. , Sauer J. , Dreiding A. S.
Published: December 2004

A new interpretation – based on a reevaluation of the spectroscopic properties of products 16 to 27 – is proposed for the reaction of diphenyl‐cyclopropen‐one 14 and ‐thione 15 with ketene‐A, N‐diacetals 8 to 13 (A  R2N, RO and RS) originally reported by Sauer & Krapf. It is concluded that the previous structural assignments (see the a‐structures), made on the assumption of a prevailing “C,C‐insertion” reaction, must be rcplaced as follows: (1) All the “secondary adducts” are, in fact, derivatives (amides and lactams) of 2,3‐diphenyl‐penta‐2, 4‐dienoic acid and thioacid (structures 16b to 24b); (2) the “isomerization products”, differ from the latter only in the configuration of the α,β‐double bond (structures 25b and 26b); (3) the common “hydrolysisproduct” is α,β‐diphenyl‐γ‐methyl‐γ‐hydroxy‐Δα‐butenolide (27b), The above cyclopropenone‐ketcneacetal reactions represent, therefore, cases of “C, N‐insertion”.

This is rationalized with a reaction scheme, in which the “acylide” structure of the “primary adducts” plays a role.
Membranelektrode zur selektiven, potentiometrischen Erfassung organischer Kationen
Authors: Scholer R. , Simon W.
Published: December 2004

A liquid ion exchanger membrane electrode responding preferentially to large onium ions is described. Selectivities of the sensor for different cations vary by factors of up to 1014 and the selectivity constants correlate closely with the corresponding exchange constants of the extracation system involved. For most cations the electrode shows theoretical response at activities >10−6M and has a life time of at least 4 months.
Heterotricyclodecane X. 2‐Oxa‐7‐thia‐isotwistan und 2‐Oxa‐7‐thia‐twistan sowie Derivate
Authors: Wigger N. , Ganter C.
Published: December 2004

The synthesis of 2‐oxa‐7‐thia‐isotwistane (11) and 2‐oxa‐7‐thia‐twistane (22) as well as of several of their derivatives is described starting from endo‐2‐hydroxy‐9‐thiabi cyclo[3.3.1]non‐6‐ene (4).

The 10O(2)‐isotwistane bromide 13, iodide 14 and tosylate 30 as well as the 10S(7)‐isotwistane iodide 15, tosylate 20, and the 10S(7)‐twistane tosylate 21 were treated under reaction conditions suitable for molecular rearrangements involving the epi‐sulfonium ion i and the oxonium ion g. respectively, by neighbouring group participation.
The Use of Intermediates with Preformed Disulfide Bridge for the Synthesis of Oxytocin and Deamino‐oxytocin
Authors: Mühlemann M. , Titov M. I. , Schwyzer R. , Rudinger J.
Published: December 2004

The disulfide‐bridged hexapeptides 6a and 6b have been prepared from benzyl‐protected intermediates. Coupling of 6a and 6b with prolyl‐leucyl‐glycine amide afforded deamino‐oxytocin (7a) and the protected oxytocin derivative 7b, respectively; the latter was converted to oxytocin (7c) by removal of the Boc protecting group.
Thermische Zerfallsreaktionen von Nitroverbindungen I: Dissoziation von Nitromethan
Authors: Glänzer K. , Troe J.
Published: December 2004

The thermal decomposition of CH3NO2 highly diluted in Ar has been studied in shock waves at 900 < T < 1500 K and 1.5 · 10−5 < [Ar] < 3.5 · 10−4 mol/cm3. Concentration profiles of CH3NO2 and NO2 were recorded. The unimolecular reaction was found to be in its fall‐off range. Limiting low pressure rate constants of k0 = [Ar] · 1017.1 exp(−42(kcal/mol)/RT) cm3/ mol sec in the range 900 < T < 1400 K and limiting high pressure rate constants of k∞ = 1016.25 exp (−(58.5 ± 0.5 kcal/mol)/RT) sec−1 have been derived. A rate constant of 1.3 · 1013 cm3/mol sec was found for the first subsequent reaction CH3+NO2 → CH3O+NO.
Die Kristallstrukturen von zwei mononuklearen Peroxotitan (IV)‐dipicolinaten
Authors: Schwarzenbach D.
Published: December 2004

The crystal structures of two mononuclear peroxotitanium(IV) chelates, the triclinic, deep red, pleochroitic diaquoperoxotitanium dipicolinate [TiO2(C7H3O4N) (H2O)2]2H2O, and the monoclinic, orange difluoroperoxotitanium dipicolinate K2[TiO2(C7H3O4N)F2]2H2O, have been determined from X‐ray diffractometer data, and refined to R = 2.7% (3488 reflections) and R = 5.1% (2324 reflections) respectively. Analogous to a yellow‐orange dinuclear peroxotitanium dipicolinate described earlier, the utanium atoms are coordinated approximately pentagonal bipyramidally, with the peroxo group and the chelate ligand occupying the equatorial sites and with H2O or F‐ forming the apices. The OO bond length in the peroxo group is the same in all structures, but there is a very slight variation of the Ti‐peroxide distances apparently connected with the colours of the compounds. The more basic the apical ligands are (H2O → F− → μ‐oxygen), the higher is the frequency of the absorption band, the longer are the Ti‐peroxide distances, and the shorter are the apical bond lengths. Difference Fourier maps based on the final structures agree with this. The red diaquo complex shows highest residual peaks between titanium and the peroxo group, whereas the orange difluoro complex shows them near the apical TiF bonds. The packing of the complexes and hydrogen bonding are discussed. HO distances seem to indicate that the very acidic diaquo complex is near a transitional state towards a hydroxonium salt.
Photochemisches Verhalten von 1‐ und 2‐alkylierten 1, 2‐Dihydronaphthalinen bei tiefen Temperaturen
Authors: Sieber W. , Heimgartner H. , Hansen H.‐J. , Schmid H.
Published: December 2004

The irradiations of 1, 1‐dimethyl‐ (8), 1, 1‐di‐(tri‐deuteriomethyl)‐ (d6–8), 1, 1, 2, 2‐tetramethyl‐ (9) and cis‐ and trans‐1, 2‐dimethyl‐1, 2‐dihydronaphthalenes (cis‐ and trans‐10) were investigated in 2, 2‐dimethylbutane/pentane at −100° using a mercury high‐pressure lamp, and with mercury high‐ and low‐pressure lamps at room temperature. The results were compared with one another, and those of the individual compounds are collected in schemes 2 and 4–7. The most important results are the following:

1. The 1, 2‐dihydronaphthalenes undergo a conrotatory ring opening to the o‐quinodimethanes on irradiation with high‐ or low‐pressure lamps at room temperature or at −100°. Thermal reactions ([1, 7a]H‐shifts, electrocyclisations) are suppressed at −100°. The o‐quinodimethanes formed from 8 (scheme 2), 9 (scheme 5) or cis‐10 (scheme 6) undergo on irradiation with the high‐pressure lamp, [1, 5]H‐shifts or photochemical Diels‐Alder reactions after renewed photochemical excitation, to yield the benzobicyclo[3.1.0]hex‐2‐ene derivatives. These Diels‐Alder reactions do not proceed stereospecifically, and therefore are not orbital symmetry controlled reactions.

2. If the 1, 2‐dihydronaphthalenes are irradiated at room temperature with either a high‐ or a low‐pressure lamp, then the initially formed o‐quinodimethanes undergo thermal [1, 7a]H‐shifts, in preference to all other reactions, as long as this is sterically possible; the resulting products can undergo secondary photochemical transformations. Such o‐quinodimethanes are formed on irradiation of 8, 9 and cis‐10. From trans‐10, an o‐quinodimethane mixture is formed, of which one component (cis, cis‐22) undergoes thermal [1, 7a] H‐shifts, while the other (trans, trans‐22) suffers a thermal disrotatory electrocyclisation to give cis‐10. If a high‐pressure lamp is used in the last experiment, then the competing photochemical Diels‐Alder cyclisation to bicyclic compounds of the type 23 (scheme 7) can result in the trans, trans‐22.

As was shown by Salisbury [3], and confirmed by ourselves in other cases [2], photochemical Diels‐Alder reactions or [1, 5]H‐shifts in the o‐quinodimethanes require light of wavelength ⩾ 400 nm (high‐pressure lamp).

The present photochemical investigations amplify and confirm our earlier conclusions concerning the photochemistry of the 1, 2‐dihydronaphthalenes [2].
Hyperfine Shifts of the 13C‐NMR. in low spin iron(III) porphyrin complexes
Authors: Wüthrich Kurt , Baumann Rudolf
Published: December 2004

The 13C‐NMR. in Zn(II)(Porphin), Fe(III)(Porphin)(CN2), Zn(II)(Tetraphenyl‐porphin), and Fe(III)(Tetraphenylporphin)(CN2) have been identified, and the 13C hyperfine shifts in the iron complexes evaluated. It was found that dipole‐dipole coupling with the electron spin localized in the π‐orbitals of the aromatic carbon atoms makes an important contribution, to the 13C hyperfine shifts. In a preliminary analysis the experimental spin density distribution obtained from the combined 1H‐ and 13C‐NMR.‐data is compared with theoretical models of the iron porphyrin complexes.
NMR.‐Study of Nitrogen Inversion and Conformation of 1,5‐Dihydro‐isoalloxazines (‘Reduced Flavin’). Studies in the flavin series, XIX. Communication
Authors: Tauscher Ludwig , Ghisla Sandro , Hemmerich Peter
Published: December 2004

The pyramidal inversion of the N(5)‐centre of several reduced flavins was measured by NMR. The inversion barrier was found to be ∼10 kcal/mol in acetone solutions and to be independent of the size of the N(5) substituent. An increase of the inversion barrier of ∼5 kcal/mol was observed in the case where the N(5) substituent could only be in axial position, and an increase of ∼3.5 kcal/mol was observed for an acyl‐like N(5) substituent. In aqueous solution the inversion barrier increases by ∼3 kcal/mol. The stereochemistry of reduced flavin and its potential relevance in flavin‐dependent biological dehydrogenations is discussed.
Über den Einfluss nichtpolarer Lösungsmittel auf Lage und Intensität von Absorptionsbanden in den Elektronenspektren apolarer Molekeln: I. Modell
Authors: Christen Heinz , Straub Peter A.
Published: December 2004

Based on the assumption that the influence of the solvent on the wavelength and intensity of the absorption spectrum of non‐polar molecules is due to Coulombic interaction of the electronic transition moments, three models are presented to calculate the wavelength and intensity changes using perturbation theory. In addition a computer program which allows to calculate solvent effects by simulation of the molecular solvent shell is developped. Using known data from solution spectra of polyenes, the experimental wavelength and intensity changes are compared with the calculated values.
Über die Biogenese des Rifamycins S
Authors: Brufani Mario , Kluepfel Dieter , Lancini Gian Carlo , Leitich Johannes , Mesentsev Albert Sergeevitch , Prelog Vladimir , Schmook Fritz Peter , Sensi Piero
Published: December 2004

Propionic acids labelled either with 14C in positions 1, 2, or 3, or with 14C in position 1 and 3H in position 3 have been used as precursors in biosynthesis of rifamycins by Streptomyces mediterranei. The resulting distribution of radioactivity in rifamycins S – as determined by systematic degradation – shows that 23 of the 37 carbon atoms in rifamycin S originate from propionic acid. This result and the distribution pattern of radioactivity are in agreement with those obtained recently by 13C‐NMR. spectroscopy [7].

The S‐methyl groups of methionin, labelled with 14C, are incorporated in rifamycins by Streptomyces mediterranei only in the methoxy group.

The consequences of these findings for the biogenesis of other ansamycins, e.g. streptovaricins, are discussed. The similarities in the constitution and configuration of ansamycins and macrolides (cf. [9]) indicate that all these microbial metabolites are formed according to the same biogenetic pattern.
Triasteranetrione
Authors: McDonald Ian A. , Dreiding André S.
Published: December 2004

Eine Synthese von Bicyclo[3.3.1]nonan‐3,7,9‐trion‐9‐(äthylen)acetal (6) durch doppelte Michael‐Addition von Aceton‐dicarbonsäure‐dimethylester (9) an Benzochinonmono(äthylen)acetal (8) und anschliessende Verseifung und Decarboxylierung des intermediären 2,4‐Dicarbomethoxy‐bicyclo[3.3.1]nonan‐3,7,9‐trion‐9‐(äthylen)acetals (10) wird beschrieben. Bromierung des Triketon‐monoacetals 6 mit Brom in Eisessig liefert 2α,4β,6α,8β‐Tetrabrombicyclo [3.3.1]nonan‐3,7,9‐trion‐9‐(äthylen)acetal (12), dessen Konfiguration sich aus dem NMR.‐Spektrum mit Hilfe von Symmetrieargumenten und aus Vergleichen von chemischen Verschiebungen ergibt. Durch Behandlung des rohen Tetrabromids (12) mit Triäthylamin entsteht ein Gemisch von 2,4‐Dibrom‐ (13) und 2,6‐Dibrom‐triasteran‐3,7,9‐trion‐9‐(äthylen)acetal (14), welches sich einerseits mit Säure zu einem 1:2‐Gemisch von 2,4‐Dibrom‐ (15) und 2,6‐Dibrom‐ triasteran‐3,7,9‐trion (16) hydrolysieren und andererseits mit Tri‐n‐butyl‐zinnhydrid zu Triaste‐ran‐3,7,9‐trion‐9‐(äthylen)acetal (17) reduktiv debromieren lässt. Hydrolyse des Triketon‐mono‐acetals (17) oder reduktive Debromierung des Triketodibromid‐Gemisches (15 und 16) führt zum hochschmelzenden, in den meisten Lösungsmitteln wenig löslichen Triasteran‐3,7,9‐trion (4). Die Spektraleigenschaften der erwähnten Substanzen werden diskutiert und zur Bestätigung der Strukturen zugezogen.
Nucleosides and Nucleotides. Part 7. Four dithymidine monophosphates with different anomeric configurations, their synthesis and behaviour towards phosphodiesterases
Authors: Séquin Urs
Published: December 2004

The four isomeric dithymidine monophosphates βTd‐βTd (1), αTd‐βTd (2), βTd‐αTd (3) and αTd‐αTd (4), differing only by the anomeric configurations of the nucleoside units, were prepared from the suitably protected nucleosides and nucleotides. The four dinucleoside monophosphates were tested as substrates of snake venom phosphodiesterase and spleen phosphodiesterase. Both enzymes accept all four compounds as substrates, however, the rate of the hydrolysis is considerably smaller if the enzymic attack takes place at the α‐nucleoside moiety of the dinucleoside monophosphate.
Sur la composition de l'arǒme de the noir V
Authors: Cazenave Paul , Horman Ian
Published: December 2004

Methyl anthranilate, geranylacetone and five lactones: γ‐valerolactone, γ‐heptalactone, γ‐décalactone, δ‐décalactone, 5‐hydroxy dec‐7‐enoic acid‐lactone have recently been identified in black tea aroma by means of GC./MS. and by sniffing the effluent from a gas chromatograph. Their intrinsic character, rather fruity and flowery, gives a certain freshness and an agreable note to the aroma.
Synthese von β‐Keto‐amidinen durch Sulfidkontraktion von Acylmethyl‐isothioharnstoffen
Authors: Heffe Wilhelm , Balsiger Rudolf W. , Thoma Klaus
Published: December 2004

N‐Substituted β‐ketoamidines are obtained readily by condensing N‐substituted thioureas 6 with α‐halogenoketones 5 and extruding the sulfur from the resulting acylmethylisothiourea 7 with triphenylphosphine (sulfide contraction).
Etude de la réactivité de la fonction carbonyle avec le cétène en présence d'un alcoxyde de titane. 1ère communication. Nouvelle méthode de synthèse de β‐hydroxyesters
Authors: Vuitel Laurent , Jacot‐Guillarmod André
Published: December 2004

A new synthesis of β‐hydroxyesters involving a reaction between a carbonyl compound, ketene and an alkyl‐orthotitanate is described.

The following carbonyl compounds have been studied: aldehydes, ketones, α‐diketones, α‐ or γ‐ketoesters. A reaction mechanism is proposed.
Etude de la réactivité de la fonction carbonyle avec le cétène en présence d'un alcoxyde de titane. 2e communication. A propos de l'interprétation de quelques spectres RMN de β‐hydroxyesters formés
Authors: Vuitel Laurent , Tabacchi Raffaele , Jacot‐Guillarmod André
Published: December 2004

The NMR. spectra of a serie of β‐hydroxyesters have been studied. It has been found that the methylene protons are magnetically nonequivalent only when the substituents on the center of asymmetry of I or II are very different. The magnetically non‐equivalence of the isopropylmethylprotons arise when the β‐hydroxyesters contain an aromatic or aromatic conjugated group directly bonded to the asymmetric carbon. The interpretation of this finding is proposed.
A Thermodynamic and Kinetic Study on the Stability of the Conformational States of N‐Acetyl‐proline‐methylamide by IR. spectroscopy and chemical relaxation
Authors: Hopmann Rudolf
Published: December 2004

N‐Acetyl‐proline‐methylamide (APMA) was synthesized by the mixed anhydride method and investigated by IR. spectroscopy and chemical relaxation measurements. The temperature‐induced variation of the IR. absorption bands of the internally hydrogen bonded (b) and of the extended, unbonded (e) species at 3330 and 3450 cm−1 respectively, were used to evaluate the molar absorptivities, a(b) = 280 and a(e) = 50 l/mol · cm, the equilibrium constant K = 0.70, and the molar enthalpy of reaction ΔH = − 2280 ± 60 cal/mol. The entropy was estimated to be in the range − 8 to − 9 e.u. The reaction rates of this conformational transition were measured by the chemical dipole field effect. The relaxation time of the rate process is τ = 2.7 · 10−9s, the rate constant for the formation of the hydrogen bond k(b) is 2.2 · 108 s−1, and that for the unfolding accompanied by the breakage of the amide hydrogen bond k(e) is 1.5 · 108s−1.
Zum Mechanismus der Imidazol‐Katalyse der Cyclo‐trimerisation undcis‐transUmlagerung von Maleinsäure‐Derivaten
Authors: Wagner‐Jauregg Th. , Ahmed Q.
Published: December 2004

A plausible explanation of the reaction mechanism is given based on addition intermediates with zwitter ion structure.
Photoinduzierte Reaktionen von 3‐Phenyl‐2H‐azirinen mit Carbonsäureestern 40. Mitteilung über Photoreaktionen
Authors: Gilgen Paul , Hansen Hans‐Jürgen , Heimgartner Heinz , Sieber Willi , Uebelhart Peter , Schmid Hans , Schönholzer Peter , Oberhänsli Willi E.
Published: December 2004

Irradiation (280–350 nm light) of a benzene solution of 3‐phenyl‐2H‐azirines 1a–e in the presence of carboxylate esters, whose carbonyl groups are activated by electron withdrawing groups situated in the acyl or alkyl moiety, produces 5‐alkoxy‐3‐oxazolines (Tab. 1 and 4, Scheme 2) isolated in 18–82% yield. These heterocycles undoubtedly originate by regiospecific addition of the ester carbonyl group to the azirine‐derived benzonitrile‐methylide ‘dipole’ (Scheme 1). The 5‐(2,′ 2′, 2′‐trifluoroethoxy)‐3‐oxazolines, derived from 2′, 2′, 2′‐trifluoroethyl carboxylic esters, on treatment with methanolic hydrogen chloride at low concentration, are smoothly transformed into the corresponding 5‐methoxy‐3‐oxazolines (e.g. 16 → 17, Tab. 5). Utilizing this process, various hitherto relatively unknown 9. 5‐alkoxy‐3‐oxazolines become accessible.

The constitution of the adducts is based essentially on spectral data. The structure of trans‐5‐methoxy‐2,4‐diphenyl‐5‐trifluoromethyl‐3‐oxazoline (trans‐14), the addition product of methyl trifluoroacetate and the benzonitrile‐benzylide from 2,3‐diphenyl‐2H‐azirine (1d), was determined by X‐ray crystallography (Section 5).

Benzonitrile‐isopropylide (22), resulting from the photochemical transformation of 2,2‐dimethyl‐3‐phenyl‐2H‐azirine (1a), also reacts with S‐methyl thiobenzoate to give 2,2‐dimethyl‐5‐methylthio‐4,5‐diphenyl‐3‐oxazoline (26). Ethyl cyanoacetate protonates predominantly the dipolar species derived from 1a at the nitrile C‐atom and yields after work‐up ethyl α‐cyano‐cinnamate (29) and ethyl isopropylidene‐cyanoacetate (30) (Scheme 4).

The relative rate of addition (krel) of benzonitrile‐isopropylide (22) to methyl α‐haloacetates and dimethyl oxalate was determined by competition experiments (Section 6). Log krel correlated satisfactorily (r = 0.97) with the pKa of the acide derived from the ester reactant: log krel = − 1.72 pKa + 2.58 or with Taft's substituent constants σ*: log krel = 2.06 σ* − 4.11 [krel(methyl dichloroacetate) = 1; Section 7.1].

On the basis of the results obtained, the mode of reaction of the so‐called benzonitrile‐methylide ‘dipole’ is discussed and a model for the transition state of addition of ester‐carbonyl groups is proposed that accounts for the observed regiospecifity and steroselectivity.
An Efficient Photosensitizer: O‐Ethyl‐1‐thionaphthoate
Authors: Gisin Markus , Wirz Jakob
Published: December 2004

The title compound is recommended as a photosensitizer for excitation by visible light of up to 500 nm due to the following properties: high triplet yield, low singlet‐triplet splitting (ET = 55 kcal/mol), low photochemical reactivity.
Zum Lumineszenzverhalten von 9‐Fluorenon
Authors: Huggenberger Christian , Labhart Heinrich
Published: December 2004

On the Luminescence of 9‐Fluorenone

The fluorescence of 9‐fluorenone has been measured in various solvents. At room temperature and for non‐hydrogen bonding solvents an emission with 19.3 ⩽ \documentclass{article}\pagestyle{empty}\begin{document}$ \widetilde\nu $\end{document}max ⩽ 21.4 · 103 cm−1 is found, whereas the fluorescence for hydrogen bonding solvents is broad and strongly red shifted, 16.7 ⩽ \documentclass{article}\pagestyle{empty}\begin{document}$ \widetilde\nu $\end{document}max ⩽ 17.5 · 103 cm−1. For these solvents also a strong temperature dependence of the emission characteristics is observed. The effects are attributed to hydrogen bonding of excited singlet fluorenone. Further, the phosphorescence of 9‐fluorenone is detected for ethanol and EPA (diethyl ether/2‐methyl‐butane/ethanol (99.5%) 5:5:2) solutions, locating the lowest triplet ππ* state at 17,600 cm−1.
The Synthesis of (S)‐(+)‐2‐Amino‐3‐(1‐adamantyl)‐propionic Acid (L‐(+)‐Adamantylalanine, Ada) as a ‘Fat’ or ‘Super’ Analogue of Leucine and Phenylalanine
Authors: Do Kim Quang , Thanei Peter , Caviezel Mario , Schwyzer Robert
Published: December 2004

Because of its overall steric resemblance to the phenylalanine analogue, carboranylalanine, the title compound was prepared by the modified Strecker synthesis of Patel & Worsley. The use of (S)‐(−)‐α‐methylbenzylamine in the synthesis, the positive trend of [α]D with increasing protonation, and the thin‐layer chromatographic behaviour of synthetic diastereomeric dipeptides are strong indications that the configuration at the asymmetric carbon atom is S (natural L). Its optical purity was ascertained by purification via the quinine and ephedrine salts of t‐butoxy‐carbonyl‐adamantylalanine. The new amino acid shall be used for studies of structure‐activity relationships of phenylalanine and leucine residues in biologically active peptides. In addition, a convenient synthesis in excellent yield of the starting material, 2‐(1‐adamantyl)‐ethanal, by Pfitzner‐Moffat oxidation of 2‐(1‐adamantyl)‐ethanol is described.
Nucleotide. X. Synthese und Eigenschaften von Dinucleosidmonophosphaten mit 2′‐Desoxyadenosin und 1‐(2′‐Desoxy‐β‐D‐ribofuranosyl)‐lumazinen als Bausteine
Authors: Charubala Ramamurthy , Pfleiderer Wolfgang
Published: December 2004

Nucleotides. X. Synthesis and properties of dinucleoside monophosphates with 2′‐deoxyadenosine and 1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐lumazines as building blocks

The synthesis of various dinucleoside monophosphates 16‐‐20 consisting of 2′‐deoxyadenosine and 1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐lumazines via the triester approach is described. The fully protected phosphotriesters 6‐‐10 as well as the partially deblocked intermediates 11‐‐15 have also been isolated and characterized by physical means. Intramolecular interactions in 16‐‐20 have been investigated by the determination of the hypochromicities and CD. spectra revealing a more or less distinct stacking effect in dependence of the 6,7‐substituents in the lumazine moiety as well as the polarity of the internucleotidic linkage. Enzymatic degradations of the dinucleoside monophosphates with snake venom and spleen phosphodiesterase are depending strongly on various structural features indicating a much lower substrate specificity especially in presence of 6,7‐diphenyl‐lumazine as an aglycone with the latter enzyme.
Formation of Dichloro Oxiranes from Ketones under Phase Transfer Conditions,
Authors: Greuter Hans , Winkler Tammo , Belluš Daniel
Published: December 2004

Compounds 2, 5 and 9 represent the first examples of isolable dichlorooxiranes formed by formal addition of dichloro carbene to a carbonyl group under phase transfer conditions. On heating, 2, 5 and 9 rearrange into α‐chloroacid chlorides 3, 6 and 10, respectively.
Die Synthese von 3β‐Acetoxy‐24‐aza‐24‐desoxa‐xysmalogenin,. Partialsynthetische Versuche in der Reihe der Herzgifte. 12. Mitteilung,
Authors: El‐Dine Shams , Faust Karin , Güntert Theodor W. , Hauser Emil , Linde Horst H. A. , Spengel Sigrid
Published: December 2004

Synthesis of 3β‐acetoxy‐24‐aza‐24‐desoxa‐xymalogenin

Starting from the pregnenolone‐derivative 1 we report the synthesis of the possibly cardiac‐active compound 24‐aza‐24‐desoxa‐xysmalogenin 15.
Two Furanosesquiterpene Marine Metabolites with Antifeedant Properties
Authors: Schulte Gary , Scheuer Paul J. , McConnell Oliver J.
Published: December 2004

Two new sesquiterpenoids, nakafuran‐8 (1) and −9 (8), have been isolated from the marine sponge Dysidea fragilis and from its prey, the nudibranchs Hypselodoris godeffroyana and Chromodoris maridadilus. The structures were established by spectral analysis and chemical transformations. Both compounds possess antifeedant properties when assayed in the laboratory against common reef fishes, Chaetodon spp.
Regioselektive Metallierung des Phenylcyclopropans sowie leichte Anlagerung des 1‐Phenylcyclopropyl‐kaliums an Äthylen
Authors: Schlosser Manfred , Schneider Philippe
Published: December 2004

Regioselective Metalation of Phenylcyclopropane and Smooth Addition of 1‐Phenylcyclopropyl Potassium onto Ethylene

Whereas pentyl sodium in pentane mainly promotes a hydrogen/metal exchange reaction at the m‐ and p‐position of phenylcyclopropane, both the butyllithium/potassium t‐butoxide reagent and trimethylsilylmethyl potassium in tetrahydrofuran convert phenylcyclopropane exclusively into 1‐phenylcyclopropyl potassium. The latter organometallic derivative adds smoothly onto the double bond of ethylene at temperatures around −40°.
Regio‐ and Stereoselective Functionalizations of Tricyclo [3.3.0.02,8]octan‐3‐one, a Potential Synthon for Polycyclopentanoid Terpenes and Prostacyclin Analogs. Preliminary Communication
Authors: Demuth Martin , Chandrasekhar Sosale , Nakano Koichi , Raghavan Palaykotai R. , Schaffner Kurt
Published: December 2004

Chemical transformation of tricyclo [3.3.0.02,8]octan‐3‐one (1) have been carried out in order to explore its potential utility as a versatile synthon for polycyclopentanoid terpenes and prostacyclin analogs. Various functionalizations of rings A and B and annulation of a third ring C were achieved in generally high yields. The system provides for a large measure of regio‐ and stereoselective reaction control.
Unambiguous Proof for Alcoxycarbonyl‐group Migration in Wagner‐Meerwein Rearrangements
Authors: Berner Daniel , Dahn Hans , Vogel Pierre
Published: December 2004

In HSO3F/SO2ClF the β‐hydroxy esters Ph‐CHOH‐CMe2‐COOR (1, RMe, Et) are doubly protonated, then transformed into the fluorosulfates 7 and (partly) into the fluorides 8. At −15°, both 7 and 8 undergo a rearrangement, forming derivatives of Me2CC(Ph)COOR (2). By labelling 1 with 13C, singly (13C(3)) and doubly (13C(1,3)), it could be shown that exclusively the ROOC groups undergo a 1,2‐shift. Compound 2 is also formed in HSO3F/SO2ClF from the isomeric Me2COH‐CHPh‐COOR (3) by elimination, and less easily from the α‐hydroxy ester Ph‐CMe2‐CHOH‐COOR (5) via a phenyl 1,2‐shift. Another isomer, Ph‐C(OH)Me‐CHMe‐COOR (4) gives products different from 2.

Using more acidic systems containing SbF5, the free carbenium ions 13 (Ph‐CH+‐CMe2‐COOR) can be stabilized; they do not form 2, possibly because of complexation of the ester group with SbF5. The energy profile and the mechanism of the rearrangement 1 → 2 are discussed.
Persistance of the Cyclopnane Radical Anions and its Relation to Structure
Authors: Gerson Fabian , Lopez Javier , Boekelheide Virgil , Hopf Henning
Published: December 2004

Reactions of [2N]cyclophanes (N = 2, ⃛6) with solvated electrons in 1,2‐di‐methoxyethane at 193 K have been studied by ESR. and ENDOR. spectroscopy. All but the two most highly bridged cyclophanes (N = 5 and 6) are reduced to paramagnetic species under these conditions. Whereas the radical anions of [2.2]‐paracyclophane and [23](1,2,4)‐ and [24](l,2,4,5)cyclophanes are sufficiently persistent to be characterized by their hyperfine data, those of the remaining five cyclophanes undergo a rapid cyclization to the radical anions of 4,5,9,10‐tetrahydropyrenes. These have been identified as the unsubstituted tetrahydropyrene (from [2.2]‐metacyclophane and [23](l,2,3)cyclophane), the 2,7‐dimethyl‐derivative (from [23](1,3,5)‐ and [24](l,2,3,5)cyclophanes) and the 1,8‐dimethyl‐derivative (from (24l,2,3,4)cyclophane). The persistence of the cyclophane radical anions seems to depend on the numbers, nmeta and npara, of the meta‐and para‐positions of the bridging ethano groups in the two benzene rings. The prerequisite for the radical anion to be persistent is nmeta⩽npara.
Steric Effects on Reaction Rates. IV. Evaluation of the Ketone Model for the Solvolysis Transition State of Secondary p‐Toluenesulfonates
Authors: Müller Paul , Blanc Jacky , Pcrlberger Jean‐Claude
Published: December 2004

The rates of solvolysis of secondary p‐toluenesulfonates in acetic acid or 97% trifluoroethanol are interpreted in terms of strain changes between substrate and the corresponding ketone. Such strain changes are obtained from force‐field calculations (ΔEst) and from equilibration of alcohols and ketones (ΔGox). This simple model reproduces the behaviour of substrates reacting by kc‐pathways to afford unstrained carbenium ions. Anchimeric assistance and leaving group hindrance in the transition state are recognized in clear‐cut cases by deviations from the expected reactivity. However, the model breaks down when highly strained carbenium ions of the cyclobutyl or 7‐norbornyl type are involved.
Acid‐Catalyzed Rearrangements of Vinylketene/Cyclopentadiene Adducts
Authors: Huston Rima , Rey Max , Drieding André S.
Published: December 2004

Säurekatalysierte Umlagerungen von Vinylketen/Cyciopentadien‐Addukten

Vier Alkyl‐vinylketene (7b–e), in situ durch 1,4‐Eleminierung von HCl aus den entsprechenden α,β‐ungesättigten Acylchloriden hergestellt, wurden mit Cyclopen‐tadien umgesetzt. Durch [2 + 2]‐Cycloaddition entstanden 7‐alkyl‐7‐vinylsubstituierte Bicyclo[3.2.0]hept‐2‐en‐6‐one 8/9. Das Stereoisomerenverhältnis 8:9 hängt von der relativen Grösse der Ketensubstituenten ab. Die Vinylketen/Cyclopen‐tadien‐Addukte 8/9 enthalten ein α‐Vinylcyclobutanon‐, ein Cope‐ und (bei 8f) ein Allylchlorid‐System. Unter dem Einfluss von Säuren (meistens BF3‐Ätherat) wurden bei 8/9 vier verschiedene Typen von Umlagerungsreaktionen beobachtet, nämlich, je nach dem Substitutionsmuster: [l,3]‐Alkyl‐Wanderungzu Bicyclo[4.3.0]‐nonadienonen 12, [l,2]‐Acyl‐Wanderung zu Bicyclo[3.3.0]octenonen 13, [3,3]‐Cope‐Umlagerung zu Bicyclo[4.2.1]nonadienonen 14 oder [l,3]‐Halogen‐Wanderung zu 7‐AlkylidenbicycIo[3.2.0]heptenonen 15. Die [l,3]‐Alkyl‐ und [l,2]‐Acyl‐Wanderun‐gen konkurrieren mit der Cope‐Umlagerung, wobei auch die Konfiguration an C(7) der Vinylketen/Cyclopentadien‐Addukte (8 bzw. 9) und das Lösungsmittel eine Rolle spielen können.
Isolierung und Strukturermittlung der neuen Cyclosporine E, F, G, H und I
Authors: Traber René , Loosli Hans‐Rudolf , Hofmann Hans , Kuhn Max , Wartburg Albert Von
Published: December 2004

Isolation and Structure Determination of the New Cyclosporins E, F, G, H und I

The cyclosporins, a new group of biologically active metabolites, are produced by the fungus Tolypocladium inflatum GAMS (formerly designated as Trichoderma polysporum [LINK EX PERS.] RIFAI). They represent neutral cyclic oligopeptides composed of 11 amino acids. In addition to the already described cyclosporins A–D new minor compounds, cyclosporins E–I, have now been isolated from the crude cyclosporin‐complex by applying extensive chromatographical separation procedures. The structures of the new compounds have been determined by spectroscopical evidence, hydrolytic cleavage and chemical correlation reactions as well as by X‐ray analysis of suitable derivatives. Cyclosporins A, B, C, D and G differ from each other only in the nature of the amino acid no. 2. Cyclosporins E and I are N‐demethylated congeners of cyclosporins A and D respectively, Cyclosporin F has been recognized as deoxycyclosporin A, whereas Cyclosporin H represents an epimeric form of cyclosporin A and contains N‐methyl‐D‐valine in position 11.
15N‐NMR Spectroscopic Characterization of Triaziridines
Authors: Hilpert Hans , Hollenstein Roger
Published: December 2004

The 15N‐NMR spectra of cis‐ and trans‐2,3‐dialkyl‐substituted triaziridines are reported. The assignment of the 15N‐NMR resonances is described, and the chemical‐shift and coupling data are compared with those of aziridines and diaziridines. The 1J(N,H) coupling constants allow one to deduce the relative configuration of the involved N‐atom. In CDCl3, a 1J(N,H) value of 58.1 ± 0.5 Hz is assigned to an NH bond cis to two lone‐pairs of electrons at neighboring N‐atoms, i.e. to the cis,trans‐triaziridines

The first stereodescriptor denotes the relative configuration of the two equal alkyl substituents, the second the relative configuration of one alkyl substituent and the H‐atom.

, and a value of 51.7 ± 0.5 Hz is assigned to a NH bond cis to only one lone‐pair of electrons, i.e. to trans, cis‐triaziridines.