bluuebunny/crossref_metadata_2025 huggingface dataset:
Dérivés C‐Glycosyliques XXXII. Synthèse de dérivés spiro‐C‐glycosylidéniques par cyclisation nucléophile. Communication préliminaire
Authors: Tronchet Jean M. J. , Gentile Bernard
Published: December 2004

C‐Glycosylic derivatives XXXII. Synthesis of spiro‐C‐glycosylidenic derivatives via nucleophilic cyclization.

On treatment with compounds bearing two nucleophilic groups as ethylenediamine, o‐phenylenediamine or their monooxa or monothia analogues, 1,2:5, 6‐di‐O‐isopropylidene‐α‐D‐ribo‐hexofuranos‐3‐ulose gave with excellent yields the corresponding spiro‐C‐glycosylidenic derivative; for example, when using o‐phenylenediamine, a spirobenzimidazoline (5) was obtained. The latter compound underwent, on oxidation, a ring expansion to a morpholinobenzimidazole (8). Spirobenzodiazepines, spirobenzooxazepines and spirobenzothiazepines were formed when applying the same type of cyclization reaction to 3‐C‐acetylmethylene‐3‐deoxy‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐ribo‐ and α‐D‐xylo‐hexofuranoses.
Photochemical reactions. VI. Photo‐Beckmann rearrangement with vinyl migration. Preliminary communication
Authors: Armengol Miguel , Coll Esperanza , Reixach María , Ribalta José M. , Repollés José , Bonet Juan‐Julio
Published: December 2004

The carefully controlled UV. irradiation of 3‐hydroxyimino‐Δ4‐ and 3‐hydroxyimino‐Δ4, Δ6‐steroids yield as a result of vinyl and alkyl migration, lactams besides products expected.
Medium Ring Compounds. XXIX. Cyclooctane‐1,5‐dione‐dioxime
Authors: Winkler Fritz K. , Seiler Paul , Chesick John P. , Dunitz Jack D.
Published: December 2004

The crystal structure of the title compound (orthorhombic a = 26.724, b = 10.899, c = 9.483 Å, space group Pna21, Z = 12) has been determined by X‐ray analysis. The structural units consist of hydrogen‐bonded trimers with approximate C3h symmetry. The results are discussed in relation to the Beckmann rearrangement of the title compound, which yields exclusively the mirror‐symmetric diamide.
The Electronic Structure of Azuleno[1,2,3‐cd]phenalene and Azuleno[5,6,7‐cd]phenalene, a Comparison
Authors: Gleiter Rolf , Spanget‐Larsen Jens , Thulstrup Erik W. , Murata Ichiro , Nakasuji Kazuhiro , Jutz Christian
Published: December 2004

The photoelectron (PE.) spectra of azuleno[l, 2, 3‐cd]phenalene (1) and azuleno‐ [5,6,7‐cd]phenalene(2) have been recorded. The first five bands of both compounds could be assigned to transitions corresponding to removal of electrons from 4a2, 6b1, 5b1, 3a2 and 4bl orbitals. This assignment is based mainly on a comparison between the observed ionization potentials and orbital energies calculated in a HMO and a PPP model.

The UV./VIS. polarized absorption spectrum of 1 in the region 10000–45000 cm−1 has been measured by means of the stretched film technique. The measurements were performed in polyethylene sheets at 77°K. Several bands could be assigned to π* ← π transitions calculated by a PPP‐CI method.

A comparison between the electronic structures of 1 and2 is made by means of a simple HMO diagram.
Komplexone XLVII. The Stability of Palladium(II) Complexes with Aminopolycarboxylate Anions
Authors: Anderegg Giorgio , Malik Subhash C.
Published: December 2004

The formation of Pd(II) complexes with aminopolycarboxylate anions has been investigated using pH and UV.‐spectrophotometric measurements at ionic strength 1 M and 20°. In some cases bromide or thiocyanate ions have been used as auxiliary ligands. Pd2+ forms the strongest complexes of the hitherto investigated divalent metal ions. The stability constants are discussed in relation to the particular stereochemistry of Pd(II) complexes.
Zum Mechanismus der photochemischen Umwandlung von 2‐Alkyl‐indazolen in 1‐Alkyl‐benzimidazole. I. Struktur und Reaktivität eines Zwischenproduktes
Authors: Heinzelmann Willy , Märky Michael , Gilgen Paul
Published: December 2004

Mechanistic studies on the photoisomerization of 2‐alkyl‐indazoles into 1‐alkyl‐benzimidazoles. I. Structure and reactivity of an intermediate.

2‐Alkyl‐indazoles (1) undergo photochemical isomerization to 1‐alkyl‐benzimidazole via previously unknown intermediates 3 (Scheme 1). In the present paper the structure and reactivity of these intermediates are discussed. Low‐temperature irradiation (−60°) of 1 b with 300 nm light gives 3 b in quantitative yield. 3 b is transformed during warm‐up to 1 b and 2 b (UV.‐evidence). The formations of 1 and 2 show the same temperature dependence but their ratio is found to be temperature‐independent. In contrast to the above behaviour, low‐temperature irradiation with 250 nm light of 3 b yields 1 b only (no 2 b). These findings are consistent with the proposed reaction mechanism 2 c in Scheme 2.

On the basis of spectroscopic properties and the described reaction pathways, it appears that the most suitable structure for intermediate 3 is a 7,8‐diaza‐tricyclo[4.3.0.07,9]nona‐2,4,6(10)‐trien (9). In Scheme 4 the reaction pathway for the iudazole‐benzimidazole‐rearrangement is summarized.
Contribution to the Problem of Nucleophilic Substitution Reactions at Small‐Ring Carbon Atoms Occurring with Retention of Configuration
Authors: Gray Robert W. , Chapleo Christopher B. , Vergnani Tiziana , Dreiding André S. , Liesner Michael , Seebach Dieter
Published: December 2004

Beitrag zum Problem der nucleophilen Substitutionsreaktionen am Kohlenstoffatom kleinerer Ringe mit Retention der Konfiguration.

Mit Natriumiodid und mit Tetraäthylammoniumacetat in Aceton findet auch unter energischen Bedingungen keine nukleophile Substitution des Bromatoms in 4‐endo‐Brom‐1,3,5,7‐tetramethyl‐anti‐tricyclo[5.1.0.03,5]octane‐2,6‐dion (10) statt, obschon bei 10 – nach neueren Anschauungen – gute Voraussetzungen für eine solche Reaktion vorhanden sein sollten. Dies bestätigt die bekannte Trägheit von Dreiring‐Kohlenstoffatomen gegenüber SN2‐Reaktionen und erhöht die Wahrscheinlichkeit, dass trotz der verwendeten Bedingungen die relativ schnellen Substitutionen der Bromatome in den Ketonen 6 und 7 durch Acetat unter Retention der Konfiguration nicht SN2‐Reaktionen sind. Ein Alternativmechanismus mit vorübergehender Öffnung des Dreirings wird für diese Umwandlungen in Betracht gezogen, und zwar 6 → 11 → 8 und 7 → 12 → 9.
Isolierung und Strukturaufklärung von Mikrolin
Authors: Bollinger Pietro , Zardin‐Tartaglia Therese
Published: December 2004

The Isolation and Structural Elucidation of Microline.

The structure and absolute configuration of microline, a new metabolite isolated from culture filtrates of Gilmaniella humicola BARRON, has been shown to be 1, by spectral data and chemical transformations, and by X‐ray analysis [4].
The Irreversible Photochemistry of Bianthrone
Authors: Korenstein R. , Muszkat K. A. , Fischer E.
Published: December 2004

A 4a,4b‐dihydrophenanthrene‐type cyclic photoisomer, the C isomer, is the major primary photoproduct of bianthrone in protic and aprotic polar solvents, and undergoes solvent‐dependent secondary reactions, including the formation of dihydrohelianthrone in protic solvents. The C isomer was shown to be formed through the singlet excited state while the B isomer is formed via the triplet manifold.
20, 21‐Azirdin‐Steroide: Reaktion von Derivaten der Oxime von 5‐Pregnen‐20‐on,9β,10α‐5‐Pregnen‐20‐on und 9β,10α‐5,7‐Pregnadien‐20‐on mit Lithiumaluminiumhydrid und von 3β‐Hydroxy‐5‐pregnen‐20‐on‐oxim mit Grignard‐Verbindungen
Authors: Tzikas Athanassios , Tamm Christoph , Boller Arthur , Fürst Andor
Published: December 2004

20, 21‐Aziridine Steroids: Reaction of Derivatives of the Oximes of 5‐Pregnen‐20‐one, 9β, 10α‐5‐Pregnen‐20‐one and 9β, 10α‐5,7‐Pregnadiene‐20‐one with Lithium Aluminium Hydride, and of 3β‐Hydroxy‐5‐pregnen‐20‐one Oxime with Grignard Reagents.

Reduction of 3β‐hydroxy‐5‐pregnen‐20‐one oxime (2) with LiAlH4 in tetrahydrofuran yielded 20α‐amino‐5‐pregnen‐3β‐ol (1), 20β‐amino‐5‐pregnen‐3β‐ol (3), 20β, 21‐imino‐5‐pregnen‐3β‐ol (6) and 20β, 21‐imino‐5‐pregnen‐3β‐ol (9). The aziridines 6 and 9 were separated via the acetyl derivatives 7 and 10. The reaction of 6 and 9 with CS2 gave 5‐(3β‐hydroxy‐5‐androsten‐17β‐yl)‐thiazolidine‐2‐thione (8). Treatment of the 20‐oximes 12 and 15 of the corresponding 9β,10α(retro)‐pregnane derivatives with LiAlH4 gave the aziridines 13 and 16, respectively. Their deamination led to the diene 14 and triene 17, respectively. Reduction of isobutyl methyl ketone‐oxime with LiAlH4 in tetrahydrofuran yielded 2‐amino‐4‐methyl‐pentane (19) as main product, 1, 2‐imino‐4‐methyl‐pentane (22) as second product and the epimeric 2,3‐imino‐4‐methyl‐pentanes 20 and 21 as minor products. – 3β‐Hydroxy‐5‐pregnen‐20‐one oxime (2) was transformed by methylmagnesium iodide in toluene to 20α, 21‐imino‐20‐methyl‐5‐pregnen‐3β‐ol (23) and 20β, 21‐imino‐20‐methyl‐5‐pregnen‐3β‐ol (26). Acetylation of these aziridines was accompanied by elimination reactions leading to 3β‐acetoxy‐20‐methylidene‐21‐N‐acetylamino‐5‐pregnene (30) and 3β‐acetoxy‐20‐methyl‐21‐N‐acetylamino‐5,17‐pregnadiene (32). The reaction of oxime 2 with ethylmagnesium bromide in toluene gave 20α, 21‐imino‐20‐ethyl‐5‐pregnen‐3β‐ol (24) and 20α,21‐imino‐20‐ethyl‐5‐pregnen‐3β‐ol (27). Acetylation of 24 and 27 led to 3β‐acetoxy‐20‐ethylidene‐21‐N‐acetylamino‐5‐pregnene (31), 3β‐acetoxy‐20‐ethyl‐21‐N‐acetylamino‐5,17‐pregnadiene 33 and 3β, 20‐diacetoxy‐20‐ethyl‐21‐N‐acetylamino‐5‐pregnene (37). With phenylmagnesium bromide in toluene the oxime 2 was transformed to 20β, 21‐imino‐20‐phenyl‐5‐pregnen‐3β‐ol (25) and 20β,21‐imino‐20‐phenyl‐5‐pregnen‐3β‐ol (28). Acetylation of 25 and 28 yielded 3β‐acetoxy‐20‐phenyl‐21‐N‐acetylamino‐5, 17‐pregnadiene (34) and 3β,20‐diacetoxy‐20‐phenyl‐21‐N‐acetylamino‐5‐pregnene (39). LiAlH4‐reduction of 39 gave 3β, 20‐dihydroxy‐20‐phenyl‐21‐N‐ethylamino‐5‐pregnene (41). – The 20, 21‐aziridines are stable to LiAlH4. Consequently they are no intermediates in the formation of the 20‐amino derivatives obtained from the oxime 2.
Etude des systèmes binaires formées par le chlorure de cyanogène et par les tétrachlorures de carbone, de silicium, de germanium et d'étain
Authors: Labaye Marie‐Hélène , Doucet André , Perrot Roger , Dubois Claude
Published: December 2004

Study of binary systems formed by cyanogen chloride and the tetrachlorides of carbon, silicon, germanium and tin.

The diagrams of binary mixtures of cyanogene chloride with the tetrachlorides of carbon, silicon, germanium and tin were studied. Only SnCl4 gives an addition compound: SnCl4 · 2ClCN. The existence of the complex was confirmed by X‐ray diffraction and vapour pressure measurements. This complex gives SnCl4 · 2NOCl on treatment with nitrosyl chloride.
A Specific Synthesis of Ethyl (2Z)‐2‐Bromomethyl‐2‐butenoate and its Conversion into Mikanecic Ester
Authors: Goldberg Ora , Dreiding André S.
Published: December 2004

Eine spezifische Synthese von (2Z)‐2‐Brommethyl‐2‐butensäure‐äthylester und seine Umwandlung in Mikanezester.

Das Lithiumsalz 12, hergestellt aus 2‐Bromorthopropensäure‐triäthylester (11) und n‐Butyl‐lithium, wurde mit Acetaldehyd umgesetzt, wobei 2‐Methyliden‐3‐hydroxy‐orthobutansäure‐triäthylester (13) und daraus, durch saure Hydrolyse, 2‐Methyliden‐3‐hydroxybutansäure‐äthylester (14) entstand. Behandlung von 14 mit N‐Bromsuccinimid und Dimethylsulfid lieferte den gewünschten (2Z)‐2‐Brommethyl‐2‐butensäure‐äthylester (6), der sich mit HBr zur entsprechenden Säure 4 hydrolysieren liess.

Die (2Z)‐Konfiguration von 4 wurde aufgrund der vicinalen 1H/13C Kopplungen zwischen H–C(3) und COOH bzw. CH2Br im 13C‐NMR.‐Spektrum bestätigt. Die 1H‐NMR.‐Signale der beiden Methylidenprotonen in 9, 11, 13 und 14 liessen sich mit Hilfe von additiven Entschirmungsbeiträgen der Substituenten um die Doppelbindung zuordnen.

1,4‐Eliminierung von HBr aus (2Z)‐2‐Brommethyl‐2‐butensäure‐äthylester (6) mit Kalium‐t‐butylat ergab Mikanezsäure‐diäthylester (21), der bei der Aufarbeitung teilweise zum Monoester 20 und zur Mikanezsäure

The systematic name for mikanecic acid (19) is 4‐vinyl‐1‐cyclohexene‐1,4‐dicarboxylic acid.

(
19
) verseift wurde.
Synthese der enantiomeren 2‐Pyrrolidinessigsäuren
Authors: Cassal Jean‐Marie , Fürst Andor , Meier Werner
Published: December 2004

Synthesis of the enantiomeric 2‐pyrrolidineacetic acids.

Starting from the enantiomeric Z‐prolines (1) the title compounds 9 were prepared in optically pure form by using the Arndt‐Eistert process. It could be shown by chemical correlation that the stereochemical determining step of the reaction sequence, the Wolff rearrangement of the N‐acylated diazomethyl ketones 5, proceeds with strict retention of configuration. Some known chiroptical methods for determination of absolute configuration were applied to the target compounds.
Physico‐Chemical Properties of Deuteriated Compounds. 2nd Communication. The isotope partition coefficient in methylcyclohexane‐hydrogen
Authors: Dessauges Gérald , Gäumann Tino
Published: December 2004

The deuterium isotope partition coefficient α has been determined as a function of total pressure, temperature and degree of deuteriation for methylcyclohexane/hydrogen over Ni/Al2O3. Good agreement with theory has been obtained for the dependence on temperature but not for that on total pressure or on the degree of deuteriation.
The Photoelectron Spectrum of Dibenzo‐p‐quinodimethane
Authors: Allan Michael , Heilbronner Edgar , Kaupp Gerd
Published: December 2004

The lowest states of dibenzo‐p‐quinodimethane radical cation are 2B1u (7.95 eV); 2B2g (8.66 eV); [2B3g, 2Au, unresolved] (9.1 eV); [2B1u, 2B2g, unresolved] (10.7 eV). This confirms the assignment proposed by Koenig et al. [1] for the states of p‐quinodimethane radical cation.
Transformations of 9 α, 10 α‐Epoxy‐Hexahydrocannabinol Acetate
Authors: Petrzilka Theodor , Prasad Kapa K. , Schmid Gérard
Published: December 2004

9α, 10α‐Epoxy‐hexahydrocannabinol acetate 1 in presence of boron trifluoride etherate rearranged to a fluoro compound 6 and to a ketone 5, and in perchloric acid to compound 11. The fluoro compound 6 had been considered erroneously in earlier literature as 4. Compounds 6 and 11 were produced by the initial opening of the epoxide followed by the acetyl transfer from the neighbouring phenolic group.

Tetrahydrocannabinol acetates 2 and 3, on oxymercuration‐demercuration followed by reduction gave the known 9α‐hydroxy‐hexahydrocannabinol (13).
Homoisoflavanone. IV. Neue Inhaltsstoffe der Eucomin‐Reihe von Eucomis bicolor
Authors: Heller Werner , Andermatt Paul , Schaad Werner A. , Tamm Christoph
Published: December 2004

Homoisoflavanones. IV. New constituents of the Eucomin Series of Eucomis bicolor.

Four new homoisoflavanones, (E)‐7‐O‐methyl‐eucomin (2a), (—)‐7‐O‐methyleucomol (5), (+)‐3,9‐dihydro‐eucomin (7a) and 7‐O‐methyl‐3,9‐dihydro‐eucomin (8), were isolated from the bulbs of Eucomis bicolor Bak. (Liliaceae). Their structures were determined by spectral data and synthesis. These compounds occur exclusively in the waxy material between the bulb leaves. Furthermore it was shown that only (Z)‐eucomin (1b) is genuine, (E)‐eucomin (1a) being an artefact. It is likely that 2a is also not genuine. A new method for a selective 7‐O‐methylation is described.
Synthèse de sucres aminés ramifiés. IV Synthèse de quelques dérivés nouveaux par l'intermédiaire d'une hexose‐spiro‐aziridine
Authors: Bourgeois Jean‐Marc
Published: December 2004

Treatment of 3‐C‐cyano‐1,2:5,6‐di‐O‐isopropylidene‐3‐O‐(toluene‐p‐sulfonyl)‐α‐D‐allofurannose with AlLiH4 yields a sugar‐spiro‐aziridine and a branched chain sulfonamide. Reaction mechanisms are briefly discussed and the configurations of the products obtained are proved by chemical reactions. With hydrogenation, the spiro compound is opened to a branched chain amino sugar with the same tertiary carbon as in vancosamine.

Several derivatives of this new compound are described: the 6‐deoxy sugars in series L and D and the pentose resulting from its oxidation by periodic acid. The conformation around C(4)–C(5) bond is deduced for three compounds from NMR. data.
The Crystal Structure of Axillarine Hydrobromide Ethanol Solvate: A Pyrrolizidine Alkaloid
Authors: Stoeckli‐Evans Helen , Crout David H. G.
Published: December 2004

The crystal structure of axillarine hydrobromide ethanol solvate has been determined from analysis of photographic X‐ray data. The crystal system is orthorhombic, space group P212121, with unit cell dimensions a = 9.89, b = 11.23, c = 20.83 Å. The structure was determined by means of Patterson and Fourier syntheses, and refined by the method of least‐squares to an R index of 9.4%.

The structural features of axillarine are noted and compared with those of several other pyrrolizidine alkaloids. The NMR. chemical shift difference between the signals due to the non‐equivalent C(9) protons in alkaloids derived from retronecine is also discussed.
Synthesis of L‐Propargylglycine and Derivatives
Authors: Leukart Othmar , Caviezel Mario , Eberle Alex , Escher Emanuel , Tun‐Kyi Aung , Schwyzer Robert
Published: December 2004

The chemical synthesis of L‐propargylglycine (L‐Pra) and of various derivatives is described. The new amino acid is a starting material for carboranylalanine (Car) and for tritiated norleucine.
Hormone‐Receptor Interactions. Synthesis and Conformational Study of cyclo‐L‐Cystathionine
Authors: Fauchère Jean‐Luc , Muthukumaraswamy Natesa , Tun‐Kyi Aung , Schwyzer Robert
Published: December 2004

The purpose of this work was to see whether the replacement of a sulfur atom in a cystine disulfide bridge by a methylene group is an only superficial ‘isosteric’ substitution, i.e. with regard to size, hydrophobia, bond angles, etc., or whether it would also encompass such parameters as preferred conformations in solution (M‐ or P‐helicity of the bridge). The methods involved the synthesis of a model compound, cyclo‐L‐cystathionine (cyclo‐L‐carbacystine), and its investigation by 1H‐ and 13C‐NMR. It is concluded that the conformations of the CH2(β)CH2(γ)SCH2(β') bridge, and of the diketopiperazine ring are closely similar to the analogous elements in cyclo‐L‐cystine (DMSO as solvent). This knowledge might help to explain the fact that carba analogs of heterodetic‐cyclic polypeptide hormones are often biologically very active.
Isolation and Identification of Three Urinary Metabolites of Retinoic Acid in the Rat
Authors: Hänni Ralph , Bigler Felix , Meister Walter , Englert Gerhard
Published: December 2004

After the intraperitoneal administration of high doses of 14C‐ and 3H‐labelled retinoic acid (1) to rats three major urinary metabolites have been isolated in microgram amounts by use of column, thin‐layer and high‐pressure liquid chromatography. Their structures were elucidated by mass spectroscopy and Fourier transform 1H‐NMR. spectroscopy as 2 (5‐methyl‐5‐[2‐(2,6,6‐trimethyl‐3‐oxo‐1‐cyclohexen‐1‐yl)vinyl]‐2‐tetrahydrofuranone), 3 (5‐[2‐(6‐hydroxymethyl‐2,6‐dimethyl‐3‐oxo‐1‐cyclohexen‐1‐yl)vinyl]‐5‐methyl‐2‐tetrahydrofuranone) and 4 (6‐(6‐hydroxymethyl‐2,6‐dimethyl‐3‐oxo‐1‐cyclohexen‐1‐yl)‐4‐methyl‐4‐hexenoic acid). In these metabolites the tetraene side chain of 1 is shortened and the cyclohexene ring oxidized. The radioactivity of 2 and 3 accounted for about 10% (0.9% of the dose) each, metabolite 4 for about 6% (0.5% of the dose) of the total urinary radioactivity.
Preferred Spatial Arrangement of the Aromatic Side Chains in Linear Oligopeptides Containing Tyrosine
Authors: Wüthrich Kurt , De Marco Antonio
Published: December 2004

1H‐NMR. studies of the protected linear tetrapeptides CF3CO‐Gly‐Gly‐L‐Tyr‐L‐Ala‐OCH3, CF3CO‐Gly‐L‐Ala‐L‐Tyr‐L‐Ala‐OCH3 and CF3CO‐Gly‐L‐Ala‐L‐Tyr‐Gly‐OCH3 showed that the side chain of the tyrosyl residue was in all three peptides preferentially oriented towards the amino terminus of the peptide chain. This preferred spatial arrangement of the aromatic side chain was manifested in the chemical shifts of the amino acid residue preceding tyrosine and in the vicinal spin‐spin coupling constants 3JHCαCβH of tyrosine.
Conversion of Penicillin to Cephalosporin Lactones. Preliminary Communication
Authors: Prasad Kapa K. , Schmid Gérard , Petrzilka Theodor
Published: December 2004

Penicillin G (1, R  CH2Ph) was converted to cephaloram‐ and 6‐epicephaloram lactones 11 and 12 respectively by the initial replacement of thiazolidine part of penicillin by the mercaptan 9 followed by intramolecular cyclization and subsequent introduction of double bond at C(3).
Zum Mechanismus der Photochemie des Benzfurazans
Authors: Heinzelmann Willy , Gilgen Paul
Published: December 2004

Mechanistic studies on the photochemical reactions of benzfurazan.

From other works it is known that irradiation of benzfurazan (1) in methanol gives the carbaminacid‐ester 4, whereas in benzene the azepinederivative 3 is obtained (Scheme 1). The compounds 5–8 (Scheme 2) have been proposed as intermediates.

In our investigations we detected and characterized by means of UV.‐ and IR.‐spectroscopy the two species 5 and 8. Irradiation of 1 with 350 nm light at room temperature in a strongly polar solvent (e.g. H2O) yields exclusively 5 (Fig. 1) with a quantum yield of 0.48. In non polar solvents (e.g. hexane) 5 isomerizes in a second photochemical step to 8 (quantum yield 0.43) (Fig. 3). Thermally, 5 can be converted back to 1. The rate constant for this reaction at room temperature is 2 · 10–5s–1.

The transformation 5 → 8 was also investigated at low temperature. There was no direct evidence for any intermediates of the type oxazirene (6) or nitrene (7). However, the formation of azepine 3 upon irradiation of 5 in benzene suggests as intermediate the nitrene 7 which could be converted into 8 in a fast thermal reaction (Scheme 3).
The Cyclopropylcarbinyl‐Cyclobutyl‐Homoallylic Rearrangement. Part III. Evidence for a symmetrical intermediate and for two discrete rearrangement processes
Authors: Geisel Manfred , Grob Cyril A. , Traber René P. , Tschudi Werner
Published: December 2004

In buffered 70% aqueous dioxane the cyclopropylcarbinyl (1‐X), endo‐cyclobutyl (2‐X) and homoallylic (3‐X) derivatives (X = nucleofuge) react to give the same mixture of alcohols 1‐OH and 3‐OH by way of a common intermediate, the symmetrical homoallylic ion 22. This follows from a study of optically active reactants 1‐X and 3‐X and from the deuterium scrambling pattern in the products from deuteriated 1‐X, endo‐2‐X and 3‐X. The high solvolysis rates of 3‐X indicated π‐bond participation in the transition state, while the high rates of 1‐X and endo‐2‐X reflect strong σ‐bond participation which is absent in exo‐2‐X.

Prolonged heating of 1‐X, endo‐2‐X and 3‐X in formic acid leads to a degenerate rearrangement of the initially formed 3‐formate. As evidenced by deuterium scrambling, carbon atoms 1, 3 and 7 eventually become positionally equivalent in the latter compound.
Synthese von Humaninsulin. III. Aufbau des geschützten zweikettigen Fragments A(14‐21) ‐ B(17‐30)
Authors: Kamber Bruno , Riniker Bernhard , Sieber Peter , Rittel Werner
Published: December 2004

Synthesis of human insulin. III. Preparation of the A(14‐21) ‐ B(17‐30) fragment.

In the recently published total synthesis of human insulin [1], one of the three principal intermediates is the protected fragment in which sequence 14‐21 of the A chain is linked to sequence 17‐30 of the B chain by the disulfide bridge between A 20 and B 19. The synthesis of this fragment, and its characterization are described in detail in the present report.

This open‐chain asymmetrical cystine peptide was prepared by elongating the two chains in the already published intermediate first with fragment A(14–19), Bpoc‐Tyr(But)‐Gln‐Leu‐Glu(OBut)‐Asn‐Tyr(But)‐NH‐NH2 (azide coupling), and secondly with fragment B(21–30), H‐Glu(OBut)‐Arg‐Gly‐Phe‐Phe‐Tyr(But)‐Thr(But)‐Pro‐Lys(Boc)‐Thr(But)‐OBut (DCCI/HOBt).
Photocyclisierungen von 1, 1'‐Polymethylen‐di‐2‐pyridonen. 46. Mitteilung über Photoreaktionen
Authors: Nakamura Yushin , Zsindely Janos , Schmid Hans
Published: December 2004

Photocyclization of 1, 1′‐Polymethylene‐di‐2‐pyridones.

Benzophenone sensitized irradiation of the four dipyridones 1‐4 gave the internal photocyclization products 6 (64%, Scheme 4), 7 (60%, Scheme 5), 8 (Scheme 6), and 11 (26%, Scheme 7), respectively. The decamethylene compound 5 yielded only polymeric material.

The primary [2+2] photoproduct 8 from dipyridone 3 (Scheme 6) is relatively unstable. Further irradiation or heating to 65° induced a Cope rearrangement to give compound 9 which, on heating to 137°, was converted into the isomeric compound 10. This product, as well as the other photoproducts mentioned, are rearranged back to their respective starting materials upon direct irradiation with 254 nm light or by heating to higher temperatures. The various possibilities for cycloadditions of pyridones are discussed as well as the possible factors which are responsible for the highly regioselective photoreactions of the dipyridones 1–4.
Concerning the Hydroxyazo‐Quinonehydrazone Equilibrium of a Trisazonaphthalene with an [18]annulene perimeter macrocyclic Aza compounds, III
Authors: Skrabal Peter , Steiger Jürg , Zollinger Heinrich
Published: December 2004

The hydroxyazo‐quinonehydrazone equilibrium of the cyclic triazonaphthalene 1 has been determined from the 1H‐NMR. spectrum of the 15N‐labelled compound. The size of the coupling constant J15N, H demonstrates that the equilibrium of 1 with respect to the non‐cyclic reference compound 6 is shifted towards the hydroxyazo form by factors of at least 5.1 and 3.9 in DMSO and H2O, respectively.
The Thermal Isomerizations of Bicyclo[2.1.0]pent‐5‐yl Methyl Ketones: endo‐exo stereomutation and cyclopropyl‐allylic rearrangement to cyclopent‐2‐enyl methyl ketones
Authors: Grosclaude Jean‐Pierre , Gonzenbach Hans‐Ulrich , Perlberger Jean‐Claude , Schaffner Kurt
Published: December 2004

Bicyclo[2.1.0]pent‐5‐yl methyl ketones undergo two thermal isomerization reactions. The endo‐exo stereomutation follows the ring‐flip path in better than 90%, with inversion of the configuration of the angular carbon atoms by cleavage and reclosure of the central bond. Stereomutation and cyclopropyl‐allylic rearrangement to cyclopent‐2‐enyl methyl ketone do not involve a common intermediate and proceed on separate potential energy surfaces. The activation parameters of the rearrangement suggest an allowed concerted cycloreversion process.
Heterotricyclodecane XXIII 2‐Thia‐7‐aza‐isotwistane
Authors: Szczepanski Henry , Ganter Camille
Published: December 2004

2‐Thia‐7‐aza‐isotwistanes.

The access to the 2‐thia‐7‐aza‐isotwistane system was achieved by water addition to the twistene 1 yielding the isotwistanol 2, characterized also as its acetate 4. Analogous D2O/D2SO4‐treatment of the twistene 1 (→ 3) allowed to deduce the reaction pathway for the formation of 2. The chloride 6, obtained from 2, on treatment with lithium aluminium hydride gave a mixture of unsubstituted isotwistane 8 and twistane 9, whereas silver acetate treatment of 6 led to the isotwistyl acetate 4 and possibly only to traces of the corresponding twistyl acetate 7.
Totalsynthese von Humaninsulin. IV. Beschreibung der Endstufen
Authors: Sieber Peter , Kamber Bruno , Hartmann Albert , Jöhl Albert , Riniker Bernhard , Rittel Werner
Published: December 2004

Total synthesis of human insulin. IV. Description of the final steps.

Recently a preliminary account was given of a new synthetic pathway leading to human insulin. In the present report the last steps of this synthesis – i.e. as from the unsymmetrical cystine derivative I – are described in detail. I contains the sequences A(14–21) and B(17–30), linked by the disulfide bridge A20‐B19. These last steps are: (1) selective removal by pH‐controlled acidolysis in trifluoroethanol of N(α)‐Trt from leucine B17, (2) completion of the B‐chain by coupling with the fragment B(1–16), (3) selective removal by trifluoroethanol of N(α)‐Bpoc at tyrosine A14, (4) completion of the A‐chain by coupling with the cyclic fragment A(1–13), (5) removal of the acid labile protecting groups, and (6) formation of the disulfide bond A7–B7 from the two S‐acetamido‐protected cysteine residues by treatment with iodine.

As judged by the composition of the reaction mixture the closure of the 85‐membered ring proceeds with a cyclization yield of over 70%. From the last step in the synthesis two products were obtained after extensive purification by counter‐current distribution: pure human insulin in a yield of 50% and its [D‐tyrosine B16]Isomer in a yield of 25%. Although the partial racemization of tyrosine B16 occurred during coupling with sequence B(1–16), the [D‐tyrosine B 16]‐stereoisomer could only be separated at the endproduct stage.

The available evidence indicates that the ease of formation of the disulfide bond A7–B7 does not depend on the precursor molecule already having an insulin‐like conformation.
Interaction between Non‐Conjugated Chromophores: 5,6‐Dimethylidene‐exo‐2‐norborneol, 5,6‐Dimethylidene‐exo, exo‐2,3‐norbornanediol and 5,6‐Dimethylidene‐2‐norbornanone
Authors: Chollet André , Mahaim Cyril , Foetisch Christophe , Hardy Michèle , Vogel Pierre
Published: December 2004

Preparation of the title compounds 11, 12 and 13 is described. Preliminary kinetic results indicate that the hydroxyl substituents in 11 and 12 have a very small retardation effect on the Diels‐Alder reactivity of 2,3‐dimethylidene‐norbornane. The keto group in 13 exerts a larger retardation effect, although it is much smaller than the retardation effect introduced by an exo‐5,6‐epoxide ring in 2,3‐dimethylidene‐norbornane.
Electrophilic Additions to Strained Bridgehead Olefins. Estimation of Strain by Comparison with the Solvolysis of Bridgehead Bromides
Authors: Becker Konrad B.
Published: December 2004

The addition of water, acetic acid, and hydrogen bromide to the strained bridge‐head olefins 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) gives exclusively the bridgehead alcohols, acetates, and bromides, respectively. The reaction rate constants for the addition of acetic acid to the bridgehead olefins 1,2 and 3, and the solvolysis rates for the related 1‐bromo‐bicyclo[3.3.1]nonane (4) and 1‐bromobicyclo[4.2.1]nonane (5) were measured. A comparison of the activation enthalpies of these two reactions gives an estimate of relative strain of the bridgehead double bond. The strain in the bicyclo[4.2.1]nonenes 2 and 3 is similar to that in trans‐cyclooctene (8‐9 kcal/mol).
Pyridinderivate als Komplexbildner. XI. Die Thermodynamik der Metallkomplexbildung mit Bis‐, Tris‐ und Tetrakis[(2‐pyridyl)methyl]‐aminen
Authors: Anderegg Giorgio , Hubmann Egon , Podder Nitya G. , Wenk Fritz
Published: December 2004

Pyridine Derivatives as Complexing Agents XI. Thermodynamics of Metal Complex Formation with Bis‐, Tris‐ and Tetrakis[(2‐pyridyl)methyl]‐amines.

The equilibria between H+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Cd2+, Pb2+, Hg2+ and Ag+, and the ligands bis(2‐pyridylmethyl)‐amine (=DPA), tris(2‐pyridylmethyl)‐amine (=TPA), tris(6‐methyl‐2‐pyridylmethyl)‐amine (=TLA) and N,N,N′,N′‐tetrakis(2‐pyridylmethyl)‐ethylenediamine (=TPEN) have been studied. Only the stability constants of DPA and TLA with almost all these cations were obtained using the pH method. For the other ligands, the complexes are already formed in acid solutions and only the use of different ligand‐ligand or metal‐metal exchanges as well as of pM methods were successful.

The protonation constants indicate that for DPA the protonation occurs firstly at the aliphatic nitrogen atom whereas in all other cases only the pyridine groups can be protonated. The thermodynamic functions of protonation are in agreement with this interpretation.

The stability constants of the complexes are often similar in magnitude to those of the analogous aliphatic amines, in spite of the much lower basicities of the pyridine derivatives. The Fe(II)N6 species of DPA and TPEN are appreciably more stable than those of the corresponding aliphatic ligands. This is due to the formation of low‐spin complexes with an unexpected ΔH value. Comparison of the thermodynamic data of formation of the complexes with TPA and TLA shows the effect of the three bulky methyl groups of the second ligand. As a consequence of steric hindrance and of the major dehydration, ΔH and less ΔS are more positive for M(TLA)2+ than for M(TPA)2+. Therefore M(TLA)2+ is normally much less stable than M(TPA)2+. The data for MnTPA2+ and ZnTPA2+ appear to indicate that in these complexes the coordination number of the metal ion is seven and four respectively. In addition to the complexes ML2+, with these two ligands hydroxo complexes ML(OH)+ are formed at remarkably low pH. Further TPEN seems to be sexidentate in the 1:1 complexes with Mn2+, Co2+ and Ni2+ but quinquedentate in those with Cu2+ and Zn2+, also in agreement with the spectra in solution and of the solid complex salts. The reaction: M(DPA)22+ + TPEN → M(TPEN)2+ + 2DPA is for all metal ions favoured by ΔH and ΔS, whereas in the case of the corresponding aliphatic ligands only by the second term. This result is explained in terms of a different magnitude of hydration of the two sexidentate ligands as a consequence of the presence of the hydrophobic aromatic rings in TPEN.
Metabolites of microorganisms. 162nd Communication. The crystal and molecular structure of lysolipin I
Authors: Dobler Max , Keller‐Schierlein Walter
Published: December 2004

The triacetate of the antibiotic lysolipin (1) crystallizes in the space group P21, a = 11.059, b = 21.453, c = 8.423 Å, β = 109.76°. X‐ray analysis was used to determine the structure of this compound.
Analyse des spectres de vibration infrarouge et Raman de benzothiazolines et de 2H‐chromènes, éléments constitutifs de spiropyrannes benzothiazoliniques. Aspect synthétique
Authors: Davin‐Pretelli Eliane , Guiliano Michel , Mille Gilbert , Chouteau Jacques , Guglielmetti Robert , Gelebart Christian
Published: December 2004

Study of infrared and Raman spectra of benzothiazolines and 2H‐chromenes, constitutive parts of benzothiazolinic spiropyrans. Synthetic aspect.

We have synthesized some benzothiazolines and some substituted 2 H‐chromenes as models of the two halves of benzothiazolinic spiropyrans with the aim of interpretation of infrared and Raman spectra of spiropyranic structure.

While doing that, we have been able to improve the synthesis method of chromenes obtained from coumarins and we have prepared new nitro‐chromenes. By studying IR. and Raman spectra of the two halves of spiropyranic molecule, we could propose a rather good attribution of fondamental modes of vibration. This attribution will used as base for the interpretation of IR. and Raman spectra of a series a benzothiazolinic spiropyrans.
Synthèse de deux nouveaux acides amines phénoliques comportant un cycle 1,2,4‐oxadiazole
Authors: Moussebois Claude , Heremans Joseph F. , Merenyi Robert , Rennerts Walthère
Published: December 2004

Synthesis of two phenolic amino acids containing the 1,2,4‐oxadiazole ring

The synthesis of α‐amino‐β [3‐(p‐hydroxyphenyl)‐1,2,4, oxadiazol‐5‐yl]propionic acid (9) and its β‐amino isomer (10) (see scheme 3) is reported. By condensation of p‐benzyloxy‐benzamide oxime and N‐benzyloxycarbonyl asparagine the derivatives 4 and 5 (see scheme 1) are obtained leading after deprotection to 9 and 10. The synthesis of N‐carboxyanhydride of 4 (6) and its corresponding amino acid (7) and amide (8) is also described.
Herstellung von Hilfsstoffen für die asymmetrische Synthese aus Weinsäure. Addition von Butyllithium an Aldehyde in chiralem Medium
Authors: Seebach Dieter , Kalinowski Hans‐Otto , Bastani Bahram , Crass Gerhard , Daum Hermann , Dörr Hennig , Dupreez Nicolaas P. , Ehrig Volker , Langer Werner , Nüssler Christa , Oei Hoc‐An , Schmidt Manfred
Published: December 2004

Preparation of Auxiliaries for Asymmetric Syntheses from Tartaric Acid. Additions of Butyllithium to Aldehydes in Chiral Media.

Chiral derivatives of the complexing 1,2‐diheterosubstituted ethanesA–Dare prepared from tartaric acid. The key starting materials are the succinic acid derivative1, the dioxolane2a, and the diamide3a. These are converted to the ethers, alkoxyamines, and alkylthio‐amines listed in the first column of Table 2 which also contains the derivatives21c, 22d, and23dmade from lactic acid, malic acid, and proline, respectively. It is shown that the highest optical yields (up to 40%) in reactions of butyllithium with aldehydes are obtained when mixtures of (−)‐1,2,3,4‐tetramethoxy‐butane (4b), (+)‐2,3‐dimethoxy‐N,N,N′,N′‐tetramethyl‐1,4‐butanediamine (17a), and (−)‐1,4‐dimethoxy‐N,N,N′,N′‐tetramethyl‐2,3‐butanediamine (14c) with pentane are used at temperatures down to −150° and ratios of auxiliary/butyllithium of up to 10:1 (see equation (1), Tables 2–4).
Photolytic closure of 4,5‐diphenyl‐oxazol‐2‐ones to phenanthro[9,10‐d]oxazol‐2‐ones and an improved synthesis of benzoins
Authors: Hakimelahi Gholamhosein H. , Boyce Charles B. , Kasmai Hamid S.
Published: December 2004

The synthesis of phenathrenes substituted by nitrogen and oxygen atoms in position 9 and 10 by photolysis of 4,5‐diphenyl‐oxazol‐2‐ones (cf. Scheme 4) is described. Moreover an improved general procedure for the synthesis of benzoins in aprotic solvent (tetra‐t‐butylammonium cyanide in DMF/DMSO) is developed.
Reaktionen mit phosphororganischen Verbindungen. XLII. Nucleophile Substitutionen an Hydroxysteroiden mit Hilfe von Triphenylphosphan/Azodicarbonsäureester
Authors: Loibner Hans , Zbiral Erich
Published: December 2004

Nucleophilic Substitution Reactions of Hydroxysteroids using Triphenylphosphane/diethylazodicarboxylate

Nucleophilic substitution reactions by means of the title reagent on various more or less hindered steroid alcohols with suitable nucleophils in benzene is described. It was not possible to run this substitution process in the hitherto used solvent THF. Cholestan‐3α‐ol (1) was transformed to the 3β‐substituted products 3β‐benzoyloxy‐cholestane (1a) and 3β‐azido‐cholestane (1b). Testosterone (2) affords with the corresponding nucleophils after short heating in benzene the inverted 17α‐substituted products 3a, 3b and 3c. Analogously the 17α‐azido‐derivative 5a arises from 17β‐hydroxy‐androst‐3‐on (4). In the presence of a ketogroup in the substrate a competitive reaction can occur as it is shown in the case of cholestan‐3‐on (6): the products are the en‐hydrazo‐dicarboxylate‐steroids 7a and 7b. The sterically very hindered 11α‐position in 11α‐hydroxy‐4‐pregnen‐3,20‐dion (8) can be transformed also to the 11β‐azide 9a. The substitution of a 6β‐hydroxy group in androstane‐3β, 6β, 17β‐triol‐3,17‐diacetate (10) to the 6α‐azide 11a affords the elimination product 12 as main component. Trans‐diaxial vicinal diols such as cholestane‐2β,3α‐diol (13) give a mixture of the α‐ and β‐oxiranes 14a and 14b.
Solubility of Organic Solvents. I. Gas Chromatographic Determination of Olive Oil‐Gas Partition Coefficients
Authors: Olivier‐Droz Pierre , Fernández José
Published: December 2004

A gas chromatographic method of measuring the olive oil‐gas partition coefficients is described. It is based on the relationship existing between the retention time of each substance and its solubility in olive oil used as a stationary liquid phase. The validity of this method has been tested by varying the length of the column, the percentage of liquid phase and the flow rate of the carrier gas. Using this technique, the partition coefficients of 24 hydrocarbons, 8 aliphatic, 6 aromatic and 10 chlorinated, have been determined (see Table 4).
Isolation, Structure Determination and Synthesis of New Acetylenic Steroids from the Sponge Calyx nicaaensis
Authors: Steiner Eric , Djerassi Carl , Fattorusso Ernesto , Magno Silvana , Mayol Luciano , Santacroce Circo , Sica Donato
Published: December 2004

Two acetylenic steroids, cholest‐5‐en‐23‐yn‐3β‐ol (5) and 26,27‐dinorcholest‐5‐en‐23‐yn‐3β‐ol (3), and another unsaturated steroidalcohol, stigmasta‐5,23‐dien‐3β‐ol (7), were isolated from the sponge Calyx nicaaensis. The structures of these two acetylenic steroids were established by synthesis. Several attempts to synthesize the marine steroids alcohol calysterol (1), with a cyclopropene‐containing side chain, starting from cholest‐5‐en‐23‐yn‐3β‐ol are also recorded. Addition of ethyl‐diazo‐acetate to the triple bond was performed, but the reduction to the methyl derivative yielded decomposition products.
Synthese von (±)‐α‐Chamigren. Vorläufige Mitteilung
Authors: Fráter György
Published: December 2004

Synthesis of (±)‐α‐Chamigrene

Cis‐ and trans‐β‐ionol (cis and trans‐1) underwent acid catalysed dehydration to a mixture of the tetraenes 2–5 in 70–80% yield (Table 1). Irradiation of this mixtures made the 6‐(Z), 8‐(Z)‐isomer 5 accessible (columns 3 and 4 in Table 1). Pyrolysis of the different mixtures at 170° showed, that both isomers, 3 and 5 respectively undergo electrocyclization to dehydrochamigrene (6). The latter was reduced to α‐chamigrene (7) by hydrogen on Lindlar catalyst.
Etudes stéréochimiques XIV. Adduits de Diels‐Alder en série résiniques; action des peracides et ouvertures acido‐catalysées d'époxydes
Authors: Maciejewski Claude , Gastambide Bernard
Published: December 2004

Studies in Stereochemistry XIV. Diels‐Alder adducts in the resin series; action of peracids and acid‐catalysed ring opening of epoxides

The synthesis of Diels‐Alder compounds of type 2 with a 17‐nor‐13(14)‐atisène skeleton is described (cf. Schemes 1–3). Depending on the nature and configuration of substituents R1 and R2 on the carbon atoms 15 and 16, an epoxide (24–33) or a ketone (35–38) or a mixture of epoxide, ketone and lactone is obtained by the action of p‐nitroperbenzoic acid on the double bond of these adducts (cf. Scheme 4). A simplified reaction scheme is suggested to explain the formation of the various products. In an acid‐catalysed reaction, the epoxides isomerize mainly into ketones. Nevertherless, in some cases, dienes (e.g. 52) or hydroxy‐γ‐lactones of (13R*, 14S*)‐configuration (e.g. 50) resulting from the opening of the epoxide ring with retention of configuration were obtained.
Hélicènes pontés: Ethano‐3,15‐ et oxa‐2‐propano‐3,15‐[7]hélicène. Synthèse, spectrographie 1H‐RMN. et étude par diffraction aux rayons X
Authors: Joly Marc , Defay Nicole , Martin Richard H. , Declerq Jean Paul , Germain Gabriel , Soubrier‐Payen Bernadette , Van Meerssche Maurice
Published: December 2004

Bridged helicenes: 3,15‐ethano‐ and 3,15‐(2‐oxapropano)‐[7]helicene

The title compounds (35 and 33, see Scheme 4) have been synthesized from a common intermediate: 3,15‐dimethoxycarbonyl‐[7]helicene (26). The conformation of the bridged [7]helicenes (X‐ray diffraction) and their 1H‐NMR. spectra have been compared to the conformation and 1H‐NMR. spectra of [7]helicene and 3,15‐dimethyl‐[7]helicene (10).
Photochemie von tricyclischen β, γ‐γ′, δ′‐ungesättigten Ketonen. 50. Mitteilung über Photoreaktionen
Authors: Hayakawa Kenji , Schmid Hans , Fráter György
Published: December 2004

Photochemistry of tricyclic β, γ‐γ′, δ′‐unsaturated ketones

The easily available tricyclic ketone 1 (cf. Scheme 1) with a homotwistane skeleton yielded upon direct irradiation the cyclobutanone derivative 3 by a 1,3‐acyl shift. Further irradiation converted 3 into the tricyclic hydrocarbon 4. However, acetone sensitized irradiation of 1 gave the tetracyclic ketone 5 by an oxa‐di‐π‐methane rearrangement. Again with acetone as a sensitizer the ketone 5 was quantitatively converted to the pentacyclic ketone 6. The conversion 5 → 6 represents a novel photochemical 1,4‐acyl shift. The possible mechanisms are discussed (see Scheme 7). The tricyclic ketone 2 underwent similar types of photoreactions as 1 (Scheme 2). Unlike 5 the tetracyclic ketone 9 did not undergo a photochemical 1,4‐acyl shift. The epoxides 10 and 14 derived from the ketones 1 and 2, respectively, underwent a 1,3‐acyl shift upon irradiation followed by decarbonylation, and the oxa‐di‐π‐methane rearrangement (Schemes 3 and 4). The diketone 18 derived from 1 behaved in the same way (Scheme 5). The tetracyclic diketone 21 cyclized very easily to the internal aldol product 22 under the influence of traces of base (Scheme 5). Upon irradiation the γ, δ‐unsaturated ketone 24 underwent only the Norrish type I cleavage to yield the aldehyde 25 (Scheme 6).
Structurally Biased 2‐Fluoroallyl Cations as Generated ‐ or not Generated ‐ in Cyclopropane Ring‐opening Reactions
Authors: Schlosser Manfred , Bessière Yvonne
Published: December 2004

The silver ion‐catalysed ring‐opening of 2‐t‐butyl‐1‐chloro‐1‐fluoro‐2‐methyl‐cyclopropane (see Scheme 2) gave the expected mixture of primary and tertiary fluoroalkenols, whereas a tricyclic analog (bornane‐spiro‐chlorofluorocyclopropane) (see Scheme 3) exclusively underwent a Wagner/Meerwein rearrangement upon ionization to lose finally a proton affording a 2‐fluoro‐1,4‐diene.
Stereoselektive reduktive Dimerisierung von α‐Cyan‐β‐(4‐pyridyl)acrylsäurederivaten
Authors: Kompis Ivan , Schönholzer Peter
Published: December 2004

Stereoselective Reductive Dimerisation of α‐Cyano‐β‐(4‐pyridyl)acrylic Acid Derivatives

Catalytic hydrogenation of the α‐substituted β‐(4‐pyridyl)acrylonitriles 3 and 4 (see Scheme 3) yields via stereoselective reductive dimerization the substituted cyclo‐pentene derivatives 7 and 8 (see Scheme 4 and 5) instead of the expected dihydro‐products 5 and 6. The mechanism of this reaction is discussed. The structure and relative configuration of 10 have been established by X‐ray single crystal analysis.
Synthese von endo‐ und exo‐1,3‐Dimethyl‐2,9‐dioxa‐bicyclo[3.3.1]nonan
Authors: Gerlach Hans , Künzler Peter
Published: December 2004

Synthesis of endo‐ and exo‐1,3‐dimethyl‐2,9‐dioxabicyclo[3.3.1]nonane

The synthesis of a host‐specific substance in norway spruce infested by Trypodendron lineatum OLIV. is described (cf. scheme 1 and 2). Alkylation of the acetyl‐acetone di‐anion (II) with 3‐methyl‐3‐buten‐1‐yl‐bromide (I) followed by sodium boro‐hydride reduction yields erythro‐ and threo‐8‐methyl‐8‐nonen‐2,4‐diol (IV and V) which are separated by chromatography. Their configurations were established by converting them under equilibrium conditions into one (VI) or two (VII and VIII) benzal derivatives. Oxidative cleavage with ozone of the terminal double bond in the erythro diol IV produces a dihydroxy ketone IX which spontaneously cyclizes to endo‐1,3‐dimethyl‐2,9‐dioxa‐bicyclo[3.3.1]nonane (X). The threo diol V is converted by the same reaction sequence exclusively into exo‐1,3‐dimethyl‐2,9‐dioxa‐bicyclo‐[3.3.1]nonane (XII). Comparison of the NMR. data of the two acetals X and XII with that of the natural product establishes the endo configuration of the latter. A second, more convenient, synthesis of a mixture of the acetals X and XII starting from the bromo‐acetal XIII is also reported.
Direct Obtention of Pure Compounds from Crude Plant Extracts by Preparative Liquid Chromatography
Authors: Hostettmann Kurt , Pettei Michael J. , Kubo Isao , Nakanishi Koji
Published: December 2004

It has been possible to submit the crude hexane extract of the barks of a medicinal plant directly to preparative liquid chromatography. A two step solvent elution gave 6 peaks, four of which readily afforded crystalline material. The entire process required 2–3 hours whereas conventional chromatography required ca. 2 weeks.
Modellrechnungen an Hexacyanoferraten und Pentacyanoferraten mit stickstoff haltigen aromatischen Liganden
Authors: Calzaferri Gion , Felix Franz
Published: December 2004

Model Calculations on Hexacyano‐ and Pentacyanoferrate Complexes with Aromatic Nitrogen Heterocycles

Using the extended Hückel method, theoretically predicted chemical, photochemical and spectroscopic properties of these complexes are compared with experimental data. A better understanding of the photochemistry is attempted by analysis of the low energy CT absorption. Starting from the amminopentacyanoferrate the spectroscopic properties of the pentacyanoferrate complexes with aromatic heterocycles are described by adding the ‘d‐π*’ MLCT and the π‐π* transitions. The results obtained on the mononuclear pyrazine compounds suggest a very simple way to understand the binuclear pyrazine complexes. Some properties of the hexacyanoferrates can be better explained if all valence orbitals of the ligands are considered. In all examples the influence of the ‘π‐backbonding’ is discussed.