bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese von optisch aktiven, natürlichen Carotinoiden und strukturell verwandten Naturprodukten. I. Synthese der chiralen Schlüsselverbindung (4R, 6R)‐4‐Hydroxy‐2,2,6‐trimethylcyclohexanon
Authors: Leuenberger Hans Georg Wilhelm , Boguth Walter , Widmer Erich , Zell Reinhard
Published: December 2004

Synthesis of optically active natural carotenoids and structurally related compounds. I. Synthesis of the chiral key compound (4R, 6R)‐4‐hydroxy‐2,2,6‐trimethylcyclohexanone.

A technical synthesis of (4R, 6R)‐4‐hydroxy‐2,2,6‐trimethylcyclohexanone (7) starting from the readily available oxo‐isophorone (2) is described. 7 is an ideal precursor for the synthesis of naturally occurring, optically active hydroxylated carotenoids (e.g. zeaxanthin, cryptoxanthin and structurally related compounds).

Chirality is introduced at C(6) by a stereoselective fermentative hydrogenation of the double bond using baker's yeast as the biocatalyst. Thereafter the carbonyl group at C(4) is reduced selectively and stereospecifically by chemical methods to the corresponding alcohol. Chemical reduction is preferably carried out by hydrogenation in the presence of a nickel catalyst or using triisobutylaluminium as the reducing agent. Stability, stereochemistry and physical properties of 7 and the stereoisomers thereof are discussed.
3″‐De‐O‐methyl‐2″,3″‐anhydro‐lankamycin, a New Macrolide Antibiotic from Streptomyces violaceoniger
Authors: Martin Jerry R. , Egan Richard S. , Goldstein Alma W. , Mueller Sandra L. , Keller‐Schierlein Walter , Mitscher Lester A. , Foltz Rodger L.
Published: December 2004

A further examination of the products from fermentation broths of Streptomyces violaceoniger has yielded small quantities of several lankamycin related antibiotics and metabolites. One of the antibiotics has been characterized as 3″‐de‐O‐methyl‐2″,3″‐anhydro‐lankamycin. The anhydro sugar of the new lankamycin, 3‐methyl‐4‐O‐acetyl‐2,3,6‐trideoxy‐α‐L‐threo‐hex‐2‐enepyranoside was also isolated as the ethyl glycoside from fermentation broths of the same organism.
Crystallographic Studies of Synthetic Corrinoids IV. Molecular Structure of a Ni(II)Oxa‐porphyrinoid from Electrochemical Oxidation of a Ni(II) Seco‐Corrin
Authors: Hodgson Keith O. , Dunitz Jack D.
Published: December 2004

X‐ray analysis of a crystalline product obtained by electrochemical oxidation of the Ni(II)‐seco‐corrinoid 1 has established the structure as that of a 1,19 oxygen‐bridged porphyrinoid 2. The crystals (perchlorate salt of 2) are triclinic, space group P1, with a = 10.205, b = 11.616, c = 14.52Å, α = 115.30, β = 107.34, γ = 85.90°, Z = 2. The structure was solved by the heavy‐atom method and refined by full‐matrix least‐squares analysis to a final R factor of 9.4%. Some features of the molecular structure are discussed.
Reactions with Stilbenes and Related Derivatives. Part I. Reactions of 1, 2‐Dihalogeno‐1, 2‐bis‐(4‐methoxyphenyl)ethanes with Alcohols
Authors: Tadros Wadie , Tadros Raouf Ramzi , Ishak Moheb Sadek
Published: December 2004

The reaction of 1, 2‐dibromo‐1, 2‐bis(4‐methoxyphenyl)ethane with alcohols was associated with rearrangement to give the corresponding bis(4‐methoxyphenyl)acetals. In boiling ethylene glycol 4,4′‐dimethoxy‐deoxybenzoin was also obtained due to an aldehyde‐ketone rearrangement. 4,4′‐Dimethoxybenzophenone was also formed being apparently derived from the acetals. The mechanism of formation of the acetals has been discussed.
A Simple Alkylative 1,2‐Carbonyl Transposition of Cyclohexenones
Authors: Oppolzer Wolfgang , Sarkar Tarun , Mahalanabis Kumar K.
Published: December 2004

Acid catalysed dehydration of the diols 5, derived from the cyclohexenone 3 affords mixtures of 8 and 11. The product ratio 8/11, although strongly dependent on both the reaction conditions and the substituent R, is independent of the diol configuration; this indicates a cationic intermediate 6. Conditions were found, which allow the sequence A → B → C → D (Scheme 2) to be applied to the syntheses of the enones 8, 21 and 25 in fair to good yields from the corresponding cyclohexenones 3, 18 and 22.
Stoffwechselprodukte von Mikroorganismen 159. Mitteilung.Über die aromatische Aminosäure des Echinocandins B: 3,4‐Dihydroxyhomotyrosin
Authors: Keller‐Schierlein Walter , Widmer Jörg
Published: December 2004

The aromatic amino acid constituent of Echinocandin B: 3,4‐Dihydroxyhomotyrosine.

The antifungal antibiotic echinocandin B gave upon treatment of its tetrahydroderivative with anhydrous trifluoroacetic acid and subsequent methanolysis the tripeptide threonyl‐(4‐hydroxyprolyl)‐(4‐oxohomotyrosine) methyl ester (8), which could be hydrolysed to 4‐oxohomotyrosine (11). These facts together with the earlier described hydrolysis of the antibiotic to 1‐amino‐3‐p‐hydroxyphenyl‐2‐propanone (6) and the reductive hydrolysis to homotyrosine suggested the presence of 3,4‐dihydroxyhomotyrosine (14) as a constituent amino acid of echinocandin B. This was confirmed by a degradation of the intact tetrahydro‐polypeptide with perjodate yielding p‐hydroxybenzaldehyde and by the isolation of free 3,4‐dihydroxyhomotyrosine upon mild acidic treatment of the tetrahydro‐polypeptide.
ESR. Spectra and Structures of Radical Anions in the Dibenzo[a, e]cyclooctene Series
Authors: Gerson Fabian , Martin William B. , Plattner Georges , Sondheimer Franz , Wong Henry N. C.
Published: December 2004

ESR. studies are reported for the radical anions of 5,6‐didehydro‐ and 5,6,11,12‐tetradehydro‐dibenzo[a,e]cyclooctene (III and IV, resp.), in addition to that of dibenzo[a,e]cyclooctene (II) itself, the spectrum of which has been reexamined. Comparison of the proton and 13C coupling constants for II·⊖, III·⊖ and IV·⊖ indicates that the three radical anions do not differ greatly in their electronic and molecular structures. This statement implies that II·⊖ should also be substantially planar, i.e., the tub‐shaped eight‐membered ring in II is expected to flatten on passing from the neutral molecule to its radical anion. Support for postulating such a change in geometry, analogous to that encountered with the parent cyclooctatetraene (I), is provided by INDO calculations.
Photochemie von in 4‐Stellung substituierten 5‐Methyl‐3‐phenyl‐isoxazolen.44. Mitteilung über Photoreaktionen
Authors: Dietliker Kurt , Gilgen Paul , Heimgartner Heinz , Schmid Hans
Published: December 2004

Photochemistry of 4‐substituted 5‐Methyl‐3‐phenyl‐isoxazoles.

4‐Trideuterioacetyl‐5‐methyl‐3‐phenyl‐isoxazole ([CD3CO]‐27), upon irradiation with 254 nm light, was converted into a 1:1 mixture of oxazoles [CD3CO]‐35 and [CD3]‐35 (Scheme 13). This isomerization is accompagnied by a slower transformation of ([CD3CO]‐27) into [CD3]‐27.

Irradiation of the isoxazole derivatives 28, 29, 30 and (E)‐31 yielded only oxazoles 36, 37, 38 and (E), (Z)‐39; no 4‐acetyl‐5‐alkoxy‐2‐phenyl‐oxazole, 2‐acetyl‐3‐methyl‐5‐phenyl‐pyrrole or 2‐acetyl‐4‐methoxycarbonyl‐3‐methyl‐5‐phenyl‐pyrrole, respectively, were formed (Scheme 9 and 10). Similarly (E)‐32 gave a mixture of (E), (Z)‐40 only (Scheme 11). Upon shorter irradiation, the intermediate 2H‐azirines (E), (Z)‐41 could be isolated (Scheme 11). Photochemical (E)/(Z)‐isomerization of the 2‐(trifluoro‐ethoxycarbonyl)‐1‐methyl‐vinyl side chain in all the compounds 32, 40 and 41 is fast.

At 230° the isoxazoles (E)‐ and (Z)‐32 are converted into oxazoles (E), (Z)‐40. The same compounds are also obtained by thermal isomerization of the 2H‐azirines (E), (Z)‐41.

The most probable mechanism for the photochemical transformations of the isoxazoles, as exemplified in the case of the isoxazole 27, is shown in Scheme 13. A benzonitrile‐methylide intermediate is postulated for the photochemical conversion of the 2H‐azirines into oxazoles. 2H‐Azirines are also intermediates in the thermal isoxazole‐oxazole rearrangement. It is however not yet clear, if the thermal 2H‐azirine‐oxazole transformation involves the same transient species as the photochemical reaction.

A mechanism for the photochemical isomerization of the 2H‐azirine 11 to the oxazole 15 is proposed (Scheme 3).
Reaktionen mit phosphororganischen Verbindungen. XLI[1]. Neuartige synthetische Aspekte des Systems Triphenylphosphin‐Azodicarbonsäureester‐Hydroxyverbindung
Authors: Loibner Hans , Zbiral Erich
Published: December 2004

New preparative methods using triphenylphosphine‐diethyl‐azodicarboxylate‐hydroxycompound.

The present paper deals with new preparative methods by which the system of triphenylphosphine‐diethylazodicarboxylate‐hydroxycompound is treated with many nucleophiles. On one side, the transformation of 5α‐cholestane‐3β‐ol to the 3α‐substituted derivatives 2a‐2e (Scheme 1) by hitherto unregarded nucleophiles like azide, cyanide, thiocyanate, trifluoroacetate and thiophenoxide is shown. Further examples demonstrate the great applicability of the reaction in the case of sensitive substrates. Cholesterol (5) is transformed to the 3α‐derivative 6a without any neighbouring group participation by the Δ5‐double bond. The analogous transformation of the hydroxysteroides 7 and 9 to the corresponding 3α‐substituted compounds 8a and 10a represent further examples to be noted. Noteworthy is also the formation of the epi‐vitamine D3‐p‐nitrobenzoate from the vitamin‐D3 itself. On the other side the sources for nucleophils require special consideration. Scheme 1 demonstarates that the anions of phosphonium salts can be used as the nucleophils as is shown by the preparation of the derivatives 2a, 2c, 2f, 2h and 2i from 5α‐cholestane‐3β‐ol (1). From scheme 2 one can see the very useful preparative fact (1→2f, 2g, 2h, 21 and 2m) that alkylhalides, alkylsulfates and alkylsulfonates can be used for supplying of the corresponding nucleophile. The possibility of a direct tosylation of a chiral hydroxycompound with inversion of configuration‐as it is shown by transformation of (S)‐2‐butanol to the tosylate, obtained also from (R)‐2‐butanol and tosylchloride is a further is a further remarkable point. The absence of neighbouring group effects allows also to prepare cis‐1, 2‐ disubstituted cyclohexane compounds type C6H10 (X) (Y) (X = N3, Cl, Y = N3, J) from the corresponding trans‐1,2‐disubstituted cyclohexanoles C6H10 (X) (OH) (X = N3, Cl). The synthesis of the compounds 14a‐15d can be regarded as representative of this new useful methodic principle.
Photochemische Synthese von 4‐Phenyl‐3‐oxazolin‐5‐onen und deren thermische Dimerisierung. 45. Mitteilung über Photoreaktionen
Authors: Gakis Nikolas , Märky Michael , Hansen Hans‐Jürgen , Heimgartner Heinz , Schmid Hans , Oberhänsli Willi E.
Published: December 2004

Photochemical Synthesis of 4‐Phenyl‐3‐oxazolin‐5‐ones and their Thermal Dimerization.

Irradiation of 3‐phenyl‐2H‐azirines affords reactive benzonitrilemethylide intermediates, which can be trapped by carbon dioxide to yield 4‐phenyl‐3‐oxazolin‐5‐ones (Scheme 1). The first section of the paper deals with the experimental description of this reaction, which already has been preliminarily communicated. Upon irradiation the 3‐oxazolin‐5‐ones undergo photoextrusion of carbon dioxide to reform the corresponding benzonitrile‐methylides, which can be trapped by dimethyl acetylenedicarboxylate.

In the second section of the paper, reactions of 2‐methyl‐4‐phenyl‐3‐oxazolin‐5‐one (3c) are described. Upon heating to 130°, this compound is partially converted to 2‐methyl‐4‐phenyl‐2‐oxazolin‐5‐one (azlactone 4e). Prolonged heating of 3c affords the dimer 7 (Scheme 3) as well as the imidazole derivative 9 (Scheme 4). Compound 7 is related to the ‘Rügheimer compound’ C18H14N2O4, formed from hippuric acid methylester. The structure of 7 was determined by X‐ray crystallography and this supports the formula assigned earlier to the ‘Rügheimer compound’ (12) and related pyrrolidin‐2,4‐diones. The possible mechanism of the thermal formation of 7, which is also base catalysed, is represented in Scheme 3, the one for the formation of the imidazol 9 in Scheme 4.

Under the influence of oxygen the 2,4‐diphenyl‐3‐oxazolin‐5‐one (3b) undergoes a dehydrodimerization to yield compound 16 (Scheme 7). Section three contains the structure elucidation of compound 16 and a mechanistic proposal for the formation of the pyrazine 19 upon thermolysis of 2,4‐diphenyl‐2‐oxazolin‐5‐on (4b, Scheme 7).
Synthese deuteriierter Derivate diastereomerer Cyclopentapeptide für die Konformationsanalyse
Authors: Möschler Hans Jörg , Tun‐Kyi Aung , Meraldi Jean‐Paul , Wüthrich Kurt , Schwyzer Robert
Published: December 2004

Synthesis of Deuteriated Derivatives of Diastereomeric Cyclopentapeptides for Use in Conformational Analysis.

The syntheses and properties of eight cyclic pentapeptides containing glycine with two deuterium atoms at C(α) (Gly*) are described: cyclo‐[‐Gly‐L‐Cys(DPM)‐Gly‐Gly*‐L‐Pro‐], cyclo‐[‐Gly*‐L‐Cys(DPM)‐Gly‐Gly*‐L‐Pro‐], cyclo‐[‐Gly‐L‐Cys‐(DPM)‐Gly‐Gly*‐D‐Pro‐], cyclo‐[‐Gly*‐L‐Cys(DPM)‐Gly‐Gly*‐D‐Pro‐], cyclo‐[‐Gly‐L‐Ala‐Gly‐Gly*‐L‐Pro‐], cyclo‐[‐Gly*‐L‐Ala‐Gly‐Gly*‐L‐Pro‐], cyclo‐[‐Gly‐L‐Ala‐Gly‐Gly*‐D‐Pro‐], and cyclo‐[‐Gly*‐L‐Ala‐Gly‐Gly*‐D‐Pro‐] (DPM = diphenylmethyl). These particular compounds were chosen in order to assign by NMR. unambiguously certain conformational features, like hydrogen‐bonding and shielding, to individual peptide bonds.
Halogenierte Pentan‐4‐olid‐carbonsäuren
Authors: Weis Claus D.
Published: December 2004

Halogenated pentane‐4‐olide carboxylic acids.

A new synthesis of halogenated pentane‐4‐olide‐4‐carboxylic acids starting from α‐methylideneglutaronitrile is reported. Different reaction conditions yielded 1,2‐dichloro‐2,4‐butane dicarboxylic acid instead, the decarboxylation of which gave access to 3‐chloro‐but‐3‐ene‐1‐carboxylic acid.
The ‘Aldol Condensation’ of Citral and Related Reactions
Authors: Thomas Alan F. , Guntz‐Dubini Renée
Published: December 2004

The reaction of citral with anhydrous base leads initially to a cyclohexa‐1,3‐dienecarbaldehyde. Stronger base and longer reaction times result in deconjugation to a cyclohexa‐1,4‐diene‐carbaldehyde, together with oxidative loss of six carbon atoms to yield 2‐methyl‐4‐(4‐methylpent‐3‐enyl)benzaldehyde. A mixed aldol reaction between citral and 3‐methyl‐2‐butenal (= senecia aldehyde) is described.
Cinchona Alkaloids. Total Synthesis of Cinchonamine. Preliminary Communication
Authors: Grethe G. , Lee H. L. , Uskokovič M. R.
Published: December 2004

Cinchona‐Alkaloide. Totalsynthese von Cinchonamin. – Zusammenfassung. Zwei verschiedene Wege zur Totalsynthese des Cinchona‐Alkaloids Cinchonamin (1) und seines C(2)‐Epimers (24) werden beschrieben. Als Ausgangsmaterial diente synthetisch hergestelltes N‐Benzoylmerochinen (2) oder sein Methylester 15.
Mehrkernige Kobaltkomplexe. I. Darstellung und Struktur von [(tren)Co(O2, OH)Co(tren)](ClO4)3·3H2O
Authors: Zehnder Margareta , Thewalt Ulf , Fallab Silvio
Published: December 2004

Polynuclear Cobalt Complexes. I. Preparation and Structure of [(tren)Co(O2, OH) ‐ Co(tren)](ClO4)3 · 3H2O.

The title compound is obtained by oxygenation of [Co(tren)(H2O)2]2+ in alcaline solution. An X‐ray structure determination shows that the tertiary nitrogen atoms of both chelate groups are cis to the O2 bridge.
Transition‐Metal Complexes with Bidentate Ligands Spanning trans‐Positions. III. Preparation and solution studies of complexes [MX(1)] (M = Cu, Ag and Au; X = anionic ligand; 1 = 2, 11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene)
Authors: Johnson D. K. , Pregosin P. S. , Venanzi L. M.
Published: December 2004

The preparation of monomeric complexes [MX(1)] is reported where M = Cu, Ag, Au; X = I, Cl, NO3, BF4 and 1 = 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene. The solution structure of the complexes is discussed on the basis of molecular weight, conductivity and NMR. measurements. In acetonitrile and nitromethane, the nitrate and fluoroborate complexes exist as ionic species [M(1)]+X− whereas the halo‐complexes are present as equilibrium mixtures of ‘covalent’ and ‘ionic’ forms. All the complexes are associated in CH2Cl2‐solutions. The values of 1J show that this association in [Ag(NO3) (1)] and [Ag(BF4) (1)] is best described in terms of ion‐pairing while that for species [AgX(1)] (X = Cl, Br and I) is mainly ‘covalent’ in nature. Evidence is presented for the formation of the complex ion [Ag(CH3CN)n(1)]+ in acetonitrile solution.
Synthese von bromosubstituierten Butenoliden II
Authors: Martin Roger , Chapleo Christopher B. , Svanholt Karen L. , Dreiding André S.
Published: December 2004

Synthesis of Bromosubstituted Butenolides II.

Methyl 4,4′‐dibromosenecioate (2) was prepared by double N‐bromosuccinimide bromination of methyl senecioate (1) and converted to methyl 4,4′‐diiodo‐senecioate (3) with sodium iodide and to 3‐bromomethyl‐2‐buten‐4‐olide (4) with aqueous hydrobromic acid. A mixture of methyl (Z)‐ and (E)‐4‐bromosenecioate (8 and 9) yielded 3‐methyl‐2‐butenolide (5) with aqueous hydrobromic acid and a mixture of (Z)‐and (E)‐4‐methoxy‐senecioic acid (10 and 11) with methanolic potassium hydroxide. N‐Bromosuccinimide treatment of the butenolide 5 afforded 4‐bromo‐3‐methyl‐2‐buten‐4‐olide (6) and 4,4‐dibromo‐3‐methyl‐2‐buten‐4‐olide (7).
L'acide hydroxylamine‐O‐sulfonique, réactif de choix pour la conversion d'aldéhydes en nitriles
Authors: Streith Jacques , Fizet Christian , Fritz Hans
Published: December 2004

Hydroxylamine‐O‐sulfonic acid: a convenient reagent for the conversion of aldehydes into nitriles.

Hydroxylamine‐O‐sulfonic acid (HAS) proved to be an excellent reagent for the conversion of aliphatic, aromatic and heteroatomic aldehydes into nitriles. There, aldehydes in the form of suspension in HAS water solution, react rapidely to give the corresponding nitriles in high yield. Only with formylpyridines could the intermediate oxime‐O‐sulfonic acids be isolated.
Nouveaux types de sucres triazotés: triazènes et phénylimino‐2‐oxadiazoles‐1,3,4. Communication préliminaire
Authors: Tronchet Jean M. J. , Rachidzadeh Faranak
Published: December 2004

Novel types of sugars bearing three nitrogen atoms: triazenes and 2‐phenylimino‐1, 3, 4‐oxadiazoles.

A series of aminodeoxysugars treated with p‐nitrobenzenediazonium tetrafluoroborate led to the corresponding triazenes, each of which in chloroform solution existing as an equilibrium between its two tautomeric forms. The free energy of activation of the exchange of the proton between the two nitrogen atoms has been estimated by variable temperature 1H‐NMR. measurements. Each triazenylsugar gave on acetylation an unique positional isomer bearing its acyl group on the nitrogen atom directly attached to the glycosyl group. Phenylsemicarbazones of two keto‐sugars were oxidized with El Khadem's reagent (I2, HgO, MgO) to give the corresponding spiro‐2‐phenylimino‐1, 3, 4‐oxadiazoles.
Photochemistry of Tricyclo[3.3.1.02,7]nonan‐6‐ones. Preliminary communication
Authors: Margaretha Paul
Published: December 2004

Sensitized irradiation (λ = 254 nm) of the title compounds 2 a and 2 b in benzene affords the tetracyclic oxetanes 3 a and 3 b. The irradiation of 2 c under similar conditions yields equal amounts of 3 c and the cyclopentadiene derivative 5. The formation of the photoproducts is discussed.
Heterotricyclodecane XXII 2‐Aza‐7‐thia‐isotwistane
Authors: Szczepanski Henry , Ganter Camille
Published: December 2004

2‐Aza‐7‐thia‐isotwistanes.

2‐Aza‐7‐thia‐isotwistanes were synthesized either starting from suitable 9‐thiabicyclo[3.3.1]nonenes by olefin‐amination (1 → 4, 2 → 5, 3 → 6, 8 → 10 and 9 → 11) as well as by intramolecular substitution (25 → 26) or by molecular rearrangement starting from twistanes (21 → 19 and 22 → 10). From the isotwistanes thus obtained several other compounds (7, 12–18, 20, 23 and 24) were prepared, too.
Isolement et identification de l'évernine dans la «mousse de chêne» (Evernia prunastri (L.) Ach.). 2e Communication
Authors: Nicollier Gilles , Tabacchi Raffaele
Published: December 2004

Isolation and identification of evernine in ‘Oakmosse’ (Evernia prunastri (L.) Ach.).

A new depside, evernin (1), has been found in the lichen Evernia Prunastri (L.) Ach. The determination of the structure and the spectral parameters of 1, especially the 13C‐NMR. spectrum, are described.
Extended Hückel Molecular Orbital Calculations for the Bridged Annulenes
Authors: Gavezzotti Angelo , Simonetta Massimo
Published: December 2004

Extended Hückel molecular orbital calculations have been performed for bridged [10], [12] and [14]annulenes. Orbital energies and wave functions were used to investigate the relative stabilities of different geometries. The theoretical results were also used to reinforce and complement available experimental information about aromaticity and reactivity of this series of molecules. Some spectroscopic properties are also discussed.
The Synthesis of Strained Methylene‐bridged Bicyclic Olefins by the Intramolecular Wittig Reaction
Authors: Becker Konrad B.
Published: December 2004

A convenient synthesis of the strained methylene‐bridged trans‐cyclooctenes bicyclo[3.3.1]‐1 (2)‐nonene (1), bicyclo[4.2.1]‐1(8)‐nonene (2), and bicyclo[4.2.1]‐1(2)‐nonene (3) by the intramolecular Wittig reaction is described (see Schemes 1–4). The (3‐oxocycloalkyl)alkyl‐phosphonium bromides 20, 27 and 38 undergoing cyclization to the bridgehead olefins are formed by simple reaction sequences. The spectral properties (IR., 1H‐NMR., 13C‐NMR., and UV.) of the olefins are discussed with regard to their strain.
Der massenspektrometrische Verlust von Vinylalkohol aus 1‐Amino‐3‐aryloxy‐2‐propanolen. 24. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen
Authors: Longoni Rita , Berntsson Peder , Bild Norbert , Hesse Manfred
Published: December 2004

Loss of vinyl alcohol from 1‐amino‐3‐aryloxy‐2‐propanols under electron impact

Under electron impact compounds of type 1 (see Scheme 1) split off 44 mass units from the molecular ion. This unusual reaction was studied using derivatives and deuterium labelled compounds. It could be demonstrated that for this fragmentation reaction 16 is the important structural feature from which H2(C3)C(2)HOH (44 mass units) is lost. The preferred reaction mechanism involves a transition state in which four members of the side chain are involved (Scheme 2, mechanism 2).
The Thermal Benzoxazinone‐Benzoxazole Conversion, a Reexecution of a Mass Spectrometric Decay by Thermolysis
Authors: Reichen Werner
Published: December 2004

The base peak in the mass spectrum of several 1,4,2‐benzoxazinone derivatives 1a–f (cf. Scheme 1 and the Table) suggests a clean carbon monoxide elimination leading to benzoxazole radical cations 2a–f. This benzoxazinone‐benzoxazole conversion can be reproduced quantitatively by flash vacuum thermolysis.

The isomeric 2,4,1‐benzoxazinone 4 (cf. Scheme 2) eliminates carbon dioxide – the resulting biradical species 5 does not recombine to benzazete 10 but fragments into nitrile and benzyne (7).
Zur Bildung polycyclischer Ketone bei der Umsetzung von 5, 6‐Dimethyliden‐bicyclo[2.2.1]hept‐2‐en mit Dieisen‐enneacarbonyl
Authors: Steiner Ulrich , Hansen Hans‐Jürgen
Published: December 2004

On the Formation of Polycyclic Ketones in the Reaction of 5, 6‐Dimethylidene‐bicyclo[2.2.1]hept‐2‐ene with Diiron‐enneacarbonyl

5,6‐Dimethylidene‐bicyclo[2.2.1]hept‐2‐ene (4), in the presence of diiron‐ennea‐carbonyl in boiling hexane, produces the endo‐and exo‐tricarbonyl‐iron complex of 4 (endo‐ and exo‐5). A mixture of numerous tricarbonyl‐iron complexes with ligands derived from coupling and carbonylation reactions of 4 are also formed. The endo‐ and exo‐5 compounds as well as two tricarbonyl‐iron complexes (7 and 8) of penta‐cyclic ketones could be isolated and characterized. After oxidative removal of the tricarbonyl‐iron groups in the reaction mixture the three pentacyclic ketones 9, 10 and 11 were separated. Structure and configuration of these ketones were deduced from spectroscopic analyses, especially from their 1H‐ and 13C‐NMR. spectra (see tables 1–4). Whereas the symmetric pentacyclic ketone 11 is of a known type (cf. [1]) the two spiroketone 9 and 10 represent compounds of a new type. Their structure and configuration shows that in ironcarbonyl induced thermal cyclopentanone formations, an exocyclic double bond can also take part.
Intramolekulare Cycloaddition von [1,1′‐Binaphthyl]‐2,2′‐bis(allylamin)
Authors: Nakamura Yushin , Zsindely Janos , Schmid Hans
Published: December 2004

Intramolecular cycloaddition of [1,1′‐binaphthyl]‐2,2′‐bis(allylamine)

Unlike the 1,1′‐binaphthyl‐2,2′‐bis(allylether) the corresponding [1,1′‐binaphthyl]‐2,2′‐bis(allylamine) (1) upon heating to 230° in mesitylene undergoes thermal decomposition only. However, when 1 is heated in a mixture of 2‐methylaminoethanol and water, besides 3 the policyclic ketones 4 and 5 are formed in isolated yields of 28 and 10%, respectively (Scheme 1). Intermediates are the imines corresponding to 4 and 5 which are hydrolysed under the reaction conditions rather than decomposed. The imines are formed by a intramolecular Diels‐Alder reaction, in which the double bond of one N‐allylgroup reacts with the naphthalene ring of the second half of the molecule.

The policyclic ketones 4 and 5 are characterized as acetates 6 and 7, respectively, and as the acetylated reduced products 11, and 12 and 13, respectively. The constitutions of all compounds are derived from spectroscopic data, chiefly from the 1H‐NMR. spectra.
Complex Formation between Sugars and the Sodium Cation in Non‐Aqueous Solvents
Authors: Grandjean Jean , Laszlo Pierre
Published: December 2004

In low dielectric solvents such as pyridine or isopropylamine, sodium perchlorate interacts strongly with a variety of sugars. The interaction is best described as non‐specific, with close proximity of the ionic partners maintained, as in a sugar‐shared ion pair.
A New Xanthone Diglucoside from Swertia perennisL.
Authors: Hostettmann Kurt , Miura Iwao
Published: December 2004

A new xanthone diglucoside (1) has been isolated from the aerial parts of Swertia perennis L. (Gentianaceae) by means of column chromatography on polyamide, followed by preparative TLC. on silica gel. From UV. and NMR. data, its structure has been established as 1,3‐di‐β‐D‐glucopyranosyl‐7,8‐dihydroxyxanthone or norswertianine‐1,3‐diglucoside.
Isolation and structure analysis of a photoproduct of the new photoaffinity label p‐nitrophenylalanine. Preliminary communication
Authors: Escher Emanuel
Published: December 2004

The isolation and structural analysis of a photoproduct of Ac · p‐nitrophenyl‐alanine ethyl ester is described and discussed. Nitrophenylalanine is proposed as a hydrogen fluoride stable photoaffinity label.
13C‐NMR. Study on Isoalloxazine and Alloxazine Derivatives
Authors: Grande Hans J. , Gast Robert , Van Schagen Cees G. , Van Berkel Willem J. H. , Müller Franz
Published: December 2004

A series of isoalloxazine and alloxazine derivatives have been investigated by 13C‐NMR. The synthesis of selectively 13C‐enriched derivatives made it possible to assign unambiguously the signals due to the quaternary carbon atoms at position 4, 4a and 10a of the isoalloxazine ring system. The assignment of the other resonances was ensured by the use of selectively deuteriated and chemically modified compounds as well as by decoupling techniques. The assignments differ in part from those published by Breitmaier & Voelter [2] on FMN and FAD. The solvent dependence of the resonances has been studied in dioxan/water mixtures. The experimental data are compared with published MO calculations and discussed.
Acetale von 1,2,3,4‐Tetraoxobutan: Herstellung und Struktur von rac‐ und meso‐2,3,3,4,4,5‐Hexamethoxy‐tetrahydrofuran
Authors: Iten Peter Xaver , Weber Hans Peter , Eugster Conrad Hans
Published: December 2004

Acetals of 1,2,3,4‐tetraoxobutane: preparation and structure determination of rac‐ and meso‐2,3,3,4,4,5‐hexamethoxy‐tetrahydrofuran

Oxidation of 3,4‐dimethoxyfuran with 2 equiv. of bromine at −75° in the presence of triethylamine and methanol leads to a mixture of rac‐ and meso‐2,3,3,4,4,5‐hexamethoxy‐tetrahydrofuran (cf. Scheme 1, 4 and 5). The structure of the crystalline rac‐compound has been determined by X‐ray analysis.
Über Pterinchemie. 61. Mitteilung. Die Kristallstruktur von 5‐Formyl‐6,7‐dimethyl‐5,6,7,8‐tetrahydropterin
Authors: Bieri Jost H. , Viscontini Max
Published: December 2004

The crystal structure of 5‐formyl‐6,7‐dimethyl‐5,6,7,8‐tetrahydropterine

The crystal structure of the title compound, a tetrahydropterine, has been determined by X‐ray analysis (direct method) and refined with 1579 structure amplitudes to R = 0.054. The crystal system is triclinic, space group P1, with unit cell dimensions a = 7.171, b = 7.255, c = 12.369 Å, α = 100.64, β = 93.32, γ = 98.27°. The tetrahydropyrazine ring exists in a distinctly flattened conformation. The C(13)‐ and C(14)‐CH3‐groups possess a cis‐configuration with axial position for C(13)‐CH3 and equatorial for C(14)‐CH3. The carbonyl‐group of the N‐formyl function has an (E)‐configuration.
Comportement an 1H‐RMN. des diaryl‐1,3‐triazènes dans les solvants neutres et acides. III
Authors: Vernin Gaston , Siv Chhan , Metzger Jacques , Elguero José , Archavlis André
Published: December 2004

1H‐NMR. behaviour of 1,3‐diaryltriazenes in neutral and acidic solvents

Formation and decomposition of 1,3‐di‐aryltriazenes can be studied by 1H‐NMR. Triazenes decompose in acidic medium or by addition of isoamylnitrite: in the last case, the spectrum shows emission lines characteristic of the CINDP effect. At −80° the prototropic rate is slow enough to permit the observation of two aromatic systems.
Thermolysis of Carbamoyl Azides. II. A. Novel Reduction of Azides with Elemental Copper
Authors: Reichen Werner
Published: December 2004

Copper(0) does not catalyze the decomposition of dialkylcarbamoyl azides 5a–e but instead it is oxidized to copper(II) while the azides 5 are reduced by uptaking one electron per molecule and eliminating nitrogen. A probable explanation for the formation of the resulting copper(II) diisocyanate diamine complexes 8a, b (see Scheme 2) as well as the other reaction products is given. A mechanism involving a carbamoyl nitrene as well as a Curtius rearrangement can be excluded.
Synthese von 5,6‐Dimethyl‐4‐oxo‐1,3,4,5‐tetrahydro‐imidazo‐[4,5‐c] [1,2,6]thiadiazin‐2,2‐dioxid und 7‐Methyl‐4‐oxo‐1H‐3,4‐dihydro‐pyrimido[4,5‐c][1,2,6]thiadiazin‐2,2‐dioxid
Authors: Edenhofer Albrecht , Meister Walter
Published: December 2004

Synthesis of 5,6‐Dimethyl‐4‐oxo‐1,3,4,5‐tetrahydro‐imidazo[4,5‐c][1,2,6]thiadiazin 2,2‐dioxide and 7‐Methyl‐4‐oxo‐1H‐3,4‐dihydropyrimido[4,5‐c][1,2,6]thiadiazin 2,2‐dioxide

The derivatives of the above heterocyclic ring systems were prepared by reaction of the corresponding o‐amino esters with sulfamoylchloride.
Synthèse et réactions de didésoxy‐5,6‐halogéno‐6‐α‐D‐xylo‐hepténo‐5‐furannurononitriles. Communication préliminaire
Authors: Tronchet Jean M. J. , Martin Olivier R.
Published: December 2004

Synthesis and reactions of 5,6‐dideoxy‐6‐halogeno‐α‐D‐xylo‐hept‐5‐eno‐furanurononitriles

The 5,6‐dideoxy‐6‐chloro‐, 6‐iodo‐ and 6‐fluoro‐3‐O‐methyl‐α‐D‐xylo‐hept‐5‐eno‐furanurononitriles have been prepared, their properties described as well as the methods used for the assignment of the configuration of the geometrical isomers. Some new reactions of the 6‐bromo analog (1) of these compounds are reported. For example, when reacted with 2‐mercaptoethanol or N,N′‐dimethyl‐ethylenediamine in the presence of NaOH, 1 gave the corresponding six‐membered ring, stereo‐isomers of an oxathiane or of a perhydrodiazine respectively. When the base used was Et3N and the binucleophile the N‐methyl‐ethanolamine or the N,N′‐dimethyl‐ethylene‐diamine the major product was a cyano‐enamine which could be hydrolysed to a β‐cyanoketone or cyclized to a five‐membered ring, an oxazolidine or an imidazolidine respectively.
Chlorine Hyperfine Splittings and Spin Density Distributions of Phenoxy Radicals. An ESR. and Quantum Chemical Study
Authors: Graf Federico , Loth Klaus , Günthard Hans‐Heinrich
Published: December 2004

ESR. spectra of the chlorine substituted phenoxy radicals listed in Table 1, which were produced by photo‐oxidation of the parent phenols in aprotic solvents, are reported. In most cases the chlorine splittings could be resolved and analysed in detail. Experimental data as well as quantum chemical calculations were used for assignment of all measured chlorine couplings and determination of their relative signs.

Spin density distributions and polarization parameters for chlorine are discussed and compared with the results from current semiempirical molecular orbital theories.

Chlorine couplings, associated with the larger splittings are found positive in sign, whereas signs of small couplings appear difficult to establish. Limitations in the applicability of McConnell or Karplus‐Fraenkel type relations to chlorine substituted aromatic radicals will be discussed and related to peculiar properties of the spin density matrix of such systems.
Struktur von Cantharidin, C10H12O4
Authors: Zehnder Margareta , Thewalt Ulf
Published: December 2004

Structure of Cantharidine, C10H12O4

An X‐ray structure determination of the title compound confirms the correctness of the molecular stereochemistry as deduced earlier from chemical considerations.
The Structure of the Antibiotic Hedamycin. I. Chemical, Physical and Spectral Properties
Authors: Séquin Urs , Bedford Colin T. , Chung Sung K. , Scott A. Ian
Published: December 2004

Interpretation of the chemical and spectral (IR., UV., 1H‐ and 13C‐NMR.) properties of the antitumor antibiotic hedamycin (C41H50N2O11) suggests that the molecule contains a methyl substituted 1‐hydroxyanthraquinone nucleus, an α, β‐unsaturated ketone, two sugar‐like tetrahydropyran rings (4 and 8) and an aliphatic chain 2, presumably with an epoxy group (see the Scheme).
Isolierung von (−)‐Dunnion aus Calceolaria integrifolia MURR. (Scrophulariaceae)
Authors: Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Isolation of (−)‐dunnione from the leaves of Calceolaria integrifolia, MURR. (fam. Scrophulariaceae)

From the leaves of Calceolaria integrifolia, a plant often used in horticulture. partially racemic (−)‐dunnione (1) has been isolated. This seems to be the first record of its occurrence outside the family Gesneriaceae, where it previously has been found in two species as the (+)‐enantiomer.
13C‐NMR. Spectra, Structure and Reactivity of Cyclic Oxocarbons
Authors: Städeli Werner , Hollenstein Roger , Von Philipsborn Wolfgang
Published: December 2004

The structures of cyclic polyketones, their hydrates and reduction products were studied in different solvents by 13C‐NMR. spectroscopy. In dimethylsulfoxide solution rhodizonic acid (1), croconic acid (2) and squaric acid (3) exhibit signal averaging. In anhydrous tetrahydrofuran 1 and 2 could be observed as non‐dynamic species. The spontaneous reactions of dodecahydroxycyclohexane (5) and decahydroxycyclopentane (‘leuconic acid’) (6) and the sequence of formation of ring‐contracted products were investigated. Key intermediates could be clearly identified which support the mechanism proposed earlier involving a benzylic acid type rearrangement followed by decarboxylation and subsequent redox reactions.
Aktivierte Chinone: Substitution von Azulenen, Benzofuran und Indolen durch 2‐Methoxycarbonyl‐1,4‐benzochinon. Regiospezifische Synthesen von Polymethoxy‐fluorenonen und eine neue Synthese des 2,6‐Dihydro‐naphtho[1,2,3‐cd]indol‐6‐on‐Systems
Authors: Tsaklidis Joannis N. , Hofer Arnold , Eugster Conrad Hans
Published: December 2004

Activated quinones: substitution reactions by methoxy‐carbonyl‐1,4‐benzoquinone of azulenes, benzofuran and indoles; regiospecific syntheses of polymethoxy‐fluorenones; a new synthesis of the 2,6‐dihydro‐naphtho[1,2,3‐cd]indol‐6‐one system.

We present new electrophilic substitution reactions of azulenes and 5‐membered heterocyclics by methoxy‐carbonyl‐1,4‐benzoquinone. Hydroquinones 3a and 5 are prepared from azulene, and 3b from guaiazulene (see Scheme 1). Benzofuran undergoes α‐ and β‐substitution (hydroquinones 9 10) (see Scheme 2). Only β‐substitution is observed with indole (hydroquinone 20) (see Scheme 4). After methylation, saponification and intramolecular acylation of the substituted indoles 22c, 22d, derivatives of 2,6‐dihydro‐naphtho[1,2,3‐cd]indol‐6‐one have been obtained. Spectral data prove the presence of the methylidenequinone tautomer. By protonation or alkylation at the carbonyl group of 23, the violet, highly delocalized 16π‐electron systems 25 are generated. Analogously, polymethoxy‐fluorenones have been prepared from methoxylated diphenylquinones 15 (see Scheme 3). They also are transformed by protonation and alkylation to the highly coloured and delocalized 12 π‐electron systems 18. By contrast, anthracene is not substituted by methoxycarbonyl‐1,4‐benzoquinone, but undergoes cycloaddition to the triptycene derivative 1 (see Scheme 1). A summary is presented of previously described reactions of activated quinones.
Synthese von Fulvenen über 1‐Chloralkyl‐acetate
Authors: Neuenschwander Markus , Iseli Rudolf
Published: December 2004

Synthesis of fulvenes via 1‐chloroaklyl‐acetates

The synthesis of fulvenes (5) via l‐chloroalkyl acetates (3) is extended to 6‐alkyl‐fulvenes with branched side‐chains, to 6‐phenylfulvene (5f) and 6‐(2‐furyl)fulvene (5g), as well as to 6‐vinylfulvenes (5h and 5i) containing chlorine and acetoxy‐substituents in ω‐position. The reaction is carried out at low temperature under water‐free conditions. The purification of the reaction products is simple. ‐ An improved procedure for the preparation of pure fulvene (5a, R=R′=H) is reported.
Neues über den Mechanismus der retentiven Substitution am Dreiring von Propellanen. Vorläufige Mitteilung
Authors: Lindner Hans Jörg , Kitschke Brigitte , Liesner Michael , Seebach Dieter
Published: December 2004

New results concerning the mechanism of retentive substitution at the three membered ring of propellanes

The reaction of the endo‐ and exo‐bromide 1a and 1b with acetate ion in aprotic polar solvents carried out at high concentrations of 1 furnishes the dimeric dehydro‐halogenation products 3a and 3b, the structures of which are determined by x‐ray crystallography (Fig. 1). The formation of 3a and 3b as well as of the products 2 of a retentive substitution process can be explained by assuming that the strained benzo‐tropones 4 are intermediates. Their high barrier to inversion is confirmed by π‐SCF‐molecular mechanics calculations.
(Z)‐5‐Tetradecen‐14‐olide, a New Macrocyclic Lactone, and Two Unsaturated Straight Chain Acetates from Ambrette Seed Absolute
Authors: Maurer Bruno , Grieder Alfred
Published: December 2004

(Z)‐5‐Tetradecen‐14‐olide (1), (Z)‐5‐dodecenyl acetate (2), and (Z)‐5‐tetradecenyl acetate (3) have been isolated from the absolute oil of Hibiscus abelmoschus L. The lactone 1 is a new macrocyclic musk compound, and the occurrence of the two acetates 2 and 3 in a plant is reported for the first time. Syntheses of the three compounds are described.
Stereoelectronic Properties, Stereospecificity and Stabilization of α‐Seleno Carbanions. An ab initio Study
Authors: Lehn Jean‐Marie , Wipff Georges , Demuynck Jean
Published: December 2004

An ab initio study of α‐seleno carbanions show that they are subject to appreciable polarization and stereoelectronic effects. Like in α‐thia carbanions, the equatorial e forms are more stable than the axial a forms, one of the stabilizing contributions being the conformation dependent (C‐lone pair, σ* SeZ) interaction. The carbanion stabilizing effect of the α‐Se atom is about 3 kcal/mol larger than that of the sulfur analog. As in the case of the sulfur no specific effect of the d orbitals is found.
Die Struktur von Cyclosporin C
Authors: Traber René , Kuhn Max , Rüegger Artur , Lichti Heinz , Loosli Hans‐Rudolf , von Wartburg Albert
Published: December 2004

The Structure of Cyclosporin C

The structure of cyclosporin C (2), a minor antifungal metabolite from Trichoderma polysporum (Link ex Pers.) RIFAI has been elucidated. Hydrolytic cleavage and spectroscopic evidence show that cyclosporin C is a neutral oligopeptide of 11 amino acids linked together in a 33‐membered ring. Cyclosporin C (2) differs from the main metabolite cyclosporin A (1) [2] [4] only by containing L‐threonine in the place of L‐α‐aminobutyric acid as has been shown by the conversion of 2 into 1. 13C‐NMR. spectra and study of molecular models suggest that cyclosporin C (2) has the same molecular conformation as 1, which is best described as a twisted β‐pleated sheet held together in a conformationally stable form by intramolecular hydrogen bonding.
Über den Mechanismus der Cope‐Umlagerung
Authors: Wehrli Rudolf , Schmid Hans , Belluŝ Daniel , Hansen Hans‐Jürgen
Published: December 2004

On the Mechanism of the Cope Rearrangement

The rates of the Cope rearrangement of 2,5‐dicyano‐3‐methyl‐hexa‐1, 5‐diene (12), (E)‐ and (Z)‐2, 5‐dicyano‐hepta‐1,5‐diene ((E)‐ and (Z)‐14) as well as of 2, 5‐dimethoxycarbonyl‐3‐methyl‐hexa‐1,5‐diene (13) and (E)‐ and (Z)‐2,5‐dimethoxycarbonyl‐hepta‐1,5‐diene ((E)‐ and (Z)‐15) were measured in decane solution in the temperature range of 50 to 150° (see Tables 5 and 8 to 12). A detailed English summary of this work is given in [1 b].
Photochemical reactions VII [1]. A ‘type A rearrangement’ in the photolysis of a steroidal α, β‐unsaturated lactone
Authors: Ferrer Vicente , Gómez José , Bonet Juan‐Julio
Published: December 2004

The irradiation of 17 β‐hydroxy‐2‐oxa‐androst‐4‐en‐3‐one (1) yield a cyclopropane derivative 2, which is the result of a rearrangement, formally analogous to the ‘type A rearrangement’ of the enones. Two other products, the dihydroxy compound 5 and the dimer 6, have also been isolated (Scheme 1).
Diterpenoide Drüsenfarbstoffe: Coleone S und T aus Plectranthus caninus ROTH(Labiatae), ein neues Diosphenol/trans‐A/B‐6,7‐Diketon‐Paar aus der Abietanreihe
Authors: Arihara Shigenobu , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Leaf‐gland Pigments: Coleons S and T from Plectranthus caninus ROTH (Labiatae), New Hydroquinones of the Abietane Series with a Diosphenol/trans‐A/B‐6,7‐Diketone Structure.

Coleons S and T were isolated from the more polar fractions from extracts of the above mentioned plant. Coleon S, C20H26O6, has been shown to have structure 1a, and coleon T, C20H26O6, structure 2.
Formation of 5‐Hydroxy‐indan‐2‐one from Attempts to Hydrolyse 9‐Ethylenedioxy‐bicyclo[3.3.1]nonane‐3,7‐dione
Authors: Chapleo Christopher B. , Dreiding André S.
Published: December 2004

Bildung von 5‐Hydroxy‐indan‐2‐on bei Hydrolyseversuchen mit 9‐Äthylendioxy‐bicyclo[3.3.1]nonan‐3,7‐dion

Verschiedene Versuche, 9‐Äthylendioxy‐bicyclo[3.3.1]nonan‐3,7‐dion (2) durch Hydrolyse in das entsprechende Triketon 3 umzuwandeln, führten nur zu 5‐Hydroxy‐indan‐2‐on (4) und in einem Fall auch noch zu etwas 7,9‐Bis(äthylendioxy)‐bicyclo‐[3.3.1]nonan‐3‐on (5). Unter milderen Hydrolysebedingungen reagierte 2 gar nicht.

Die Bildung von 4 aus 2 wird über eine Wagner‐Meerwein‐Umlagerung und nach‐folgende Eliminierung von Äthylenglycol formuliert. Das so entstandene Äthylenglycol reagiert mit noch vorhandenem Acetal 2 zum Bis‐acetal 5, was als weitere Bestätigung der Resistenz von 2 gegen Hydrolyse gelten darf.
Electrochemical Reduction of Cyclohex‐2‐enones
Authors: Tissot Paul , Margaretha Paul
Published: December 2004

The electrochemical reduction of the cyclohex‐2‐enones 1a–1e (mercury cathode, CH3CN, Bu4NBF4) was studied by means of cyclic voltammetry, d.c. polarography, coulometry and chemical product analysis. Compounds 1a–1c give a mixture of the hydrodimers 4 and 5 via formation of the radical anion 2 by an irreversible one electron transfer, followed by protonation and dimerization of the allylic radical 3. The 6‐halocyclohex‐2‐enones 1d and 1e exhibit two distinct reduction waves. The first corresponds to an irreversible two electron transfer with formation of the halide anion and the enolate anion 6 which gives 1b by protonation. The second wave corresponds to a quasi‐reversible one electron transfer to 6 to afford the radical dianion 7 (Scheme 2).
Isomerism and Protonation of α‐Diazocarbonyl Compounds. A Molecular Orbital Study
Authors: Niemeyer Hermann M.
Published: December 2004

CNDO/2, MINDO/3 and ab initio molecular orbital calculations are used in a study of conformational isomerism, protonation site and mechanism of protonation of the title compounds.
n‐π‐Interaction in Enamines and Enaminoketones. A 15N‐NMR. Study
Authors: Schwotzer Willi , Von Philipsborn Wolfgang
Published: December 2004

15N‐Chemical shifts of 32 enamines, 11 enaminoketones and 28 closely related amines have been determined with the isotope in natural abundance. In order to eliminate substituent effects, differential chemical shifts Δδ(N) are defined as δN(amine)‐δN(enamine). This parameter is shown to correlate well with the free enthalpy of activation ΔG# for restricted rotation about the NC(α) bond in enamines with extended conjugation. Δδ(N) values of substituted anilinostyrenes correlate also with 13C‐chemical shifts of the β‐carbon in the enamine system and with Hammett σ‐constants of the aniline substituents. The experimental results suggest that differential 15N shifts are a useful probe to study n, π‐interaction in enamines.
Neue Cyclopeptide aus Trichoderma polysporum (LINK EX PERS.) RIFAI: Die Cyclosporine B, D und E
Authors: Traber René , Kuhn Max , Loosli Hans‐Rudolf , Pache Walter , Von Wartburg Albert
Published: December 2004

New Cyclopeptides from Trichoderma polysporum (LINK EX PERS.) RIFAI: Cyclosporins B, D and E

Cyclosporins represent a new group of biologically active metabolites produced by Trichoderma polysporum (LINK EX PERS.) RIFAI and other fungi imperfecti. The structures of the main components, cyclosporins A (1) and C(3) have been determined as neutral cyclic oligopeptides composed of 11 amino acids, among them a new C9‐amino acid [2–4]. In addition, three minor metabolites, cyclosporins B, D and E, have now been isolated and characterized. Chemical investigation, spectroscopic evidence and X‐ray analysis led to the structural formulae of cyclosporins B (2) and D (4). Both compounds have the same sequence of amino acids as cyclosporin A (1), with the exception of L‐α‐aminobutyric acid, replaced in cyclosporin B (2) by L‐alanine and in cyclosporin D (4) by L‐valine, respectively. Cyclosporins undergo a characteristic intramolecular N,O‐acyl migration to furnish the corresponding basic isocompounds. The antifungal activities of cyclosporins are reported.
Synthese, Kristallstruktur und thermische Entwässerung von CsMnF4 · 2H2O
Authors: Dubler Erich , Linowsky Lothar , Matthieu Jean‐Pierre , Oswald Hans‐Rudolf
Published: December 2004

Synthesis, crystal structure and thermal dehydration of CsMnF4 · 2H2O

The preparation of a new fluoromanganate (III)‐complex CsMnF4 · 2H2O is reported. It crystallizes in the monoclinic space group C2 with a = 11.891(2) Å, b = 6.589(1) Å, c = 10.558(1) Å, β = 131.46(1)° and Z = 4. The crystal structure has been solved from diffractometer data by heavy‐atom methods and refined to a conventional R‐value of 1.8% (including the contributions of three hydrogen atoms in measured and one in calculated positions). The structure is characterized by isolated, tetragonally distorted [MnF4(OH2)2]‐octahedra with Mn‐F‐distances from 1.801(8) Å to 1.870(7) Å and Mn‐O‐distances of 2.146(6) Å and 2.268(6) Å. Cesium exhibits an irregular 10‐coordination by 8 F‐atoms and 2 O‐atoms (mean values for the two independent cesium ions: Cs‐F = 3.17 Å and 3.21 Å, Cs‐O = 3.32 Å and 3.29 Å). The [MnF4(OH2)2]‐octahedra are connected to six neighbouring octahedra by hydrogen bonding.

The dehydration of the complex has been studied by thermoanalytical methods and power x‐ray‐diffractometry. The unit cell of the dehydrated compound, CsMnF4, is tetragonal with a = 7.936(1) Å and c = 6.341(1) Å. A close relationship to the structure of CsFeF4, which is a superstructure variant of the T1A1F4‐type[6], is indicated by the similarity of the corresponding unit cells and preliminary structure factor calculations. A proposition for the crystal structure of CsMnF4 is developed on the basis of (2 + 2 + 2)‐orthorhombic distorted MnF6‐octahedra.