bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proxiphomin und Protophomin, zwei neue Cytochalasane
Authors: Binder Michael , Tamm Christoph 
Published: December 2004

AbstractTwo new cytochalasans, proxiphomin and protophomin have been isolated from cultures of a Phoma species (strain S 298). They are shown to possess the same skeleton as deoxaphomin (4), which has been isolated recently. Thus they represent lower states of oxidation of 4. On the basis of the spectral data, the structures 16‐methyl‐10‐phenyl‐[13]cytochalasa‐6 (7), 13t,21t‐triene‐1,23‐dione (1) and 16‐methyl‐10‐phenyl‐[13]cytochalasa‐5 (6)13t,21t‐triene‐1,7,23‐trione (2) are proposed for proxiphomin and protophomin respectively. On treatment with perchloric acid, substance 1 is isomerized to give 16‐methyl‐10‐phenyl‐10‐pheny‐10‐phenyl‐[13]cytochalasa‐5(6)13t,21t‐triene‐1,23‐dione (3). The assumption that the [13]cytochalasans are potential biogenetic precursors of the 24‐oxa‐[14]catochalasans is discussed.
Vinca Alkaloids XXXII. Microbiological conversions of vindoline, a major alkaloid from vinca rosea L
Authors: Neuss N. , Fukuda D. S. , Mallett G. E. , Brannon D. R. , Huckstep L. L. 
Published: December 2004

AbstractVindoline, a major alkaloid from Vinca rosea L was subjected to microbiological conversion using Streptomyces cultures.Several new metabolites were isolated and their structures elucidated.
Substituenteneinfluss bei der massenspektrometrischen Fragmentierung: Untersuchungen an N‐methyl‐β,β′‐diphenyl‐diäthylaminen. 19. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen
Authors: Weibel Peter A. , Hesse Manfred 
Published: December 2004

AbstractSome different substituted N‐methyl‐β,β′‐diphenyl‐diethylamines (I) were investigated mass spectrometrically. The main fragmentations and their genesis are summarized in Scheme 2. The molecular ion generates the major fragmentions a (m/e 148) and b (m/e (147 + X)); c (m/e 105) is formed from a and d (m/e (104+X)) from b by further decomposition. The logarithms of the ratios of the relative ion intensities a/b, c/a and d/b were correlated according to the Hammett equation with different substituent constants. The following correlation coefficients (at 20ev) were found: r = 0,98 (σ+), r = 0,63 (σ) and r = 0,96 (σ) respectively. On the basis of the above Hammett correlations, the value of this kind of investigation for the elucidation of mass spectral fragmentation mechanisms is discussed.
Thermodynamics of Mixtures Excess Volumes and Energies of Mixing of Cycloalkane Mixtures (Cyclopentane to Cyclooctane)
Authors: Duc Luong Minh , Abdellah Z. , Stoeckli H. F. 
Published: December 2004

AbstractThe volumes of mixing for the systems cyclopentane + cyclohexane, cyclopentane + cycloheptane, cyclohexane + cycloheptane (at 20°C), and cyclopentane + cyclooctane, cyclohexane + cyclooctane, cycloheptane + cyclooctane (at 30 °C) have been measured with a dilatometer. All systems show volume contractions, except the first. The energies of mixing are also given. They vary from 7 to 55 J/mol for equimolar solutions.
Photochemische Cycloadditionen von 3‐phenyl‐2h‐azirinen mit Aldehyden. 31. Mitteilung über Photoreaktionen
Authors: Giezendanner Heinz , Heimgartner Heinz , Jackson Barry , Winkler Tammo , Hansen Hans‐Jürgen , Schmid Hans 
Published: December 2004

AbstractExperiments concerning the photochemical condensation of 3‐phenyl‐2H‐azirines 1 with aliphatic and aromatic aldehydes to 3‐oxazolines 4 are fully described (cf. scheme 1). Photochemically nitrile methylides of type 2 are first formed, which then very quickly react thermally with the aldehydes in a regiospecific manner to give the 3‐oxazolines 4. Azirines monosubstituted in position 2 (lb and 1c) give mixtures of cis, trans‐oxazoline isomers, in which the cis isomer predominates. The stereoselectivity of the cycloaddition reaction can be rationalized by a simple model (scheme 10).The stereoisomeric 3‐oxazolines 4 are distinguishable in the NMR. spectra by the large homoallylic coupling constants between the H atoms on C(2) and C(5).
13C‐NMR. Spectra of Pteridines
Authors: Müller Georges , Philipsborn Wolfgang Von 
Published: December 2004

Abstract13C‐NMR. spectra of pterin, xanthopterin, isoxanthopterin, leucopterin, lumazine and of the model compounds isocytosine and desamino‐isocytosine have been measured as anions and cations in 1 M NaOD, CF3COOH, H2SO4 and FSO3H solutions. The spectra were analysed by means of heteronuclear double resonance, with the aid of non‐decoupled spectra, and by spectral comparison. The results are interpreted in terms of the ionisation state of the pteridines in the four solvents and are compared with those obtained from 1H‐NMR. spectroscopy.
The Crystal Structure of 5,5′,7,7′‐tetramethyl‐3,3′,9‐triethyl thiacarbocyanine perchlorate
Authors: Stoeckli‐Evans Helen 
Published: December 2004

AbstractThe crystal structure of the title compound has been determined by X‐ray crystallographic analysis from diffractometer data. The compound is found to exist in the crystalline state as the mono‐cis isomer (a). The conjugated chain is in a folded configuration and the two sulfur atoms are on opposing sides. It is the first time such a mono‐cis isomer has been analysed by X‐ray crystallography.
Un nouveau type de sucres azotés, les gem‐azo‐alcools. Communication préliminaire
Authors: Tronchet Jean M. J. , Rachidzadeh Faranak , Tronchet Jeannine 
Published: December 2004

AbstractTreatment of keto‐sugar p‐nitrophenylhydrazones with lead tetraacetate led to the corresponding gem‐azo‐acetates. The reaction is highly stereoselective, only one of the two possible epimers at the new asymmetric carbon being formed in measurable quantity. Catalytic de‐acylation of these gem‐azo‐acetates yielded, quantitatively, representatives of a new class of nitrogen‐containing sugars: the gem‐azo‐alcohols. When treated with potassium t‐butylate, the gem‐azoacetates underwent a rearrangement with ring expansion leading to N‐aminolactams.
Consequences of Substitution in the Photoelectron Spectra of [2, 2]Paracyclophanes: Separation of ‘through‐space’ and ‘through‐bond’ interactions as a consequence of fluorosubstitution
Authors: Heilbronner Edgar , Maier John P. 
Published: December 2004

AbstractThe PE. spectra of [2, 2]paracyclophane (1), 4‐amino[2, 2]paracyclophane (2) and 1, 1, 2, 2, 9, 9, 10, 10‐octafluoro[2, 2]paracyclophane (3) are presented. The bands corresponding to ejection of the photoelectron from the five highest occupied π‐orbitals have been assigned. The ‘observed’ orbital energies (i.e. the negative ionization potentials) are discussed in terms of ‘through space’ and ‘through‐bond’ interactions between the semi‐localized π‐orbitals (e1g) of the benzene moieties and the C, C‐σ‐orbitals of the ethylene bridges.The PE. spectrum of 3 shows that the fluorine‐induced lowering of the C, C‐σ‐orbital energy effectively ‘turns‐off’ the ‘through‐bond’ interaction. The resulting pattern of the first four bands confirms the assignment given for 1.Finally the band shifts induced by an amino group in position 4 are again in agreement with this assignment. Attention is drawn to the phenomenon of ‘orbital switching’ as a consequence of substitution in loosely coupled systems such as 1.
Synthesis and Ring Opening of 1, 4‐Dicyanobicyclo[2.2.0]hexane. Radical stabilization energy of a cyano group. Preliminary Communication
Authors: Belluš Daniel , Rist GüNther 
Published: December 2004

Abstract1, 4‐Dicyanobicyclo[2.2.0]hexane (2) was prepared by (2+2)‐photocycloaddition of ethylene to 1, 2‐dicyanocyclobutene. 2 isomerizes cleanly to 2, 5‐dicyanohexadiene‐1, 5 (3) with a very low activation energy of 21.7 ± 1.4 kcal/mol. From comparison with the reported rates of isomerization of bicyclo[2.2.0]hexane, the radical stabilization energy of the cyano group is shown to be about 7.3 kcal/mol.
Contribution à la phytochimie du genre Gentiana. V. Identification d'un nouveau O‐glucoside de C‐glucoside flavonique dans les feuilles de Gentiana nivalis L
Authors: Hostettmann Kurt , Jacot‐Guillarmod André 
Published: December 2004

AbstractA new flavonic heteroside, isoorientin‐3′‐O‐glucoside, has been isolated from leaves of Gentiana nivalis L. by means of column chromatography on polyamide. The determination of the structure is described.
Umwandlung von 6‐Methylen‐tricyclo[3.2.1.02,7]oct‐3‐en‐8‐onen mit Ameisensäure in kernmethylierte Phenylessigsäuren
Authors: Peter‐Katalinić Jasna , Zsindely Janos , Schmid Hans 
Published: December 2004

AbstractIn a preceding communication [5] it was shown that 1, 5‐dimethyl‐6‐methylene‐tricyclo[3.2.1.02,7]oct‐3‐en‐8‐one (2) and related tricyclic ketones are converted by strong acids (CF3COOH, FSO3H) into polymethylated tropylium salts with loss of carbon monoxide, e.g. the 1, 2, 4‐trimethyltropylium ion 4 from 2 (Scheme 1).Under the influence of neat formic acid at 20°, 2 gives rise to ring‐methylated phenylacetic acids, i.e. 2, 4, 5‐trimethylphenylacetic acid (5, main product) as well as smaller amounts of 2, 4, 6‐and 2, 3, 5‐trimethylphenylacetic acids (6, 7 resp.; Scheme 2). –On rearrangement of 2 in HCOOD, ca. 2 D‐atoms are incorporated (formula d2‐5) into the 2, 4, 5‐trimethylphenylacetic acid.The tricyclic 15, containing 3 methyl groups, gives 2, 3, 5, 6‐tetramethylphenylacetic acid (11; Scheme 4) with formic acid; the isomeric tricyclic 16, 2, 3, 4, 5‐tetramethylphenylacetic acid (12; Scheme 5). From 1, 2, 4, 5‐tetramethyl‐6‐methylene‐tricyclo[3.2.1.02,7]oct‐3‐en‐8‐one (17) one obtains pentamethylphenylacetic acid (14; Scheme 6). Similarly from 18, a phenylacetic acid derivative, most probably 4‐ethyl‐2, 5‐dimethyl‐phenylacetic acid (19; Scheme 17), has been obtained. –In no case was the formation of α‐phenylpropionic acid derivatives observed, not even from the tricyclic 23 containing six methyl groups.From the tricyclic ketone 2 in 70% formic acid a trimethyl‐cyclohepta‐2, 4, 6‐triene‐1‐carboxyclic acid with partial formula 24, besides 2, 4, 5‐trimethylphenylacetic acid (5), is formed. 24 remained practically unchanged on standing in neat formic acid and thus does not represent an intermediate product arising by the rearrangement of 2 in that solvent.On standing in methanolic sulfuric acid, tricyclic 2 furnishes the two stereioisomeric methanol‐addition products Z‐26 and E‐26 (Scheme 10); these are converted into the phenylacetic acids 5, 6 and 7 by neat formic acid.The conversion of 2 and related compounds into ring‐polymethylated phenylacetic acids, represents a novel and rather complicated reaction. In our opinion the reaction paths represented in Schemes 12 and 18 are responsible for the conversion of 2 into the trimethylphenylacetic acids, compound 40 representing a key intermediate. Analogous reaction paths can be assumed for the other tricyclic ketone transformations.The use of shift reagents in the NMR. spectroscopy and the high‐resolution gas‐chromatography of the corresponding methyl esters proved particularly important for the analysis of the reaction mixtures. The majority of the polymethylated phenylacetic acids were independently synthesised by means of the Willgerodt‐Kindler reaction (chap. 3.2.), whose course is strongly influenced by methyl groups in the ortho‐positions of the acetophenone derivatives employed.
Oscillations chimiques du système BrO/Ce4+/acétylacétone. Communication préliminaire
Authors: Janjic DéSimir , Stroot Philippe , Burger Ulrich 
Published: December 2004

AbstractTemporal chemical oscillations occurring in the BrO3−/Ce4+/acetylacetone system have been investigated by three different methods: potentiometry, calorimetry and NMR. spectrometry. In spite of the analogy between acetylacetone and malonic acid, this periodic reaction seems to be rather different from the famous Belousov‐Zhabotinsky reaction.
Darstellung und Hydrolyse von Poly(dimethylsilyl)benzolen: Benzo[c][1,2,5]oxadisilole
Authors: Fink Walter 
Published: December 2004

AbstractPoly(dimethylsilyl)benzenes have been prepared by ‘in situ’ reactions of polybromobenzenes with magnesium and dimethylchlorosilane in tetrahydrofuran. The hydrolysis of these compounds yields benzo[c][1,2,5]oxadisiloles.
Metal Complexes with Macrocyclic Ligands, IV. Synthesis, Properties and Kinetics of Complexation with Three N‐methyl Substituted 1,4,8,11‐tetraazacyclotetradecanes
Authors: Buxtorf Rudolf , Kaden Thomas A. 
Published: December 2004

AbstractThe synthesis, properties and complexation of 1‐methyl‐1,4,8,11‐tetraazacyclotetradecane (1‐MeCyclam‐14), 1,5‐dimethyl‐1,5,8,12‐tetraazacyclotetradecane (2‐MeCyclam‐14) and 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane (4‐MeCyclam‐14) are described.While the Ni2+ and Cu2+ complexes of 1‐MeCyclam‐14 and 2‐MeCyclam‐14 exhibit square planar geometries, 4‐MeCyclam‐14 forms Ni2+ and Cu2+ complexes, whose absorption spectra are best explained by assuming pentaco‐ordination of the metal ions.The complexation rate of the three N‐methyl substituted macrocycles with Cu2+ and Ni2+ is slower than can be accounted for by water exchange and little affected by introducing methyl groups at the nitrogens. Both results are in contrast to what is known for open chain amine ligands. A mechanism for the complexation is proposed, which also explains why the products of the reaction of 4‐MeCyclam‐14 with Cu2+ and Ni2+ are pentaco‐ordinated.
Notiz zur Darstellung von N‐Trimethylsilylmethyl‐glycin und einiger seiner Derivate
Authors: Fink Walter 
Published: December 2004

AbstractEs wird eine einfache Darstellung von N‐Trimethylsilylmethyl‐glycin durch Hydrolyse von N‐Trimethylsilylmethyl‐glycinamid beschrieben.
Steroide und Sexualhormone. 252. Mitteilung [1]. Chiroptische Eigenschaften einiger an C(5) stereoisomerer 3‐Oxo‐4,4‐dimethyl‐steroide
Authors: Snatzke Günther , Graf Walter , Schlatter Hans‐Rudolf , Lüthy Christoph 
Published: December 2004

AbstractThe chiroptical properties of the C(5)‐epimeric 4,4‐dimethyl‐steroidderivatives 6, 7 and 8, recently prepared [1], are reported.
Welkstoffe und Antibiotika. 42.Mitteilung [1]. Zur Synthese des Orchinols
Authors: Steiner Kurt , Egli Christian , Rigassi Norbert , Helali Salah Eldin , Hardegger Emil 
Published: December 2004

AbstractOrchinol (Va) ist durch Reduktion und Hydrogenolyse aus dem Dehydroorchinol‐benzyläther (I) oder durch Kondensation des Hydroxy‐tetralons IIIa mit Methylvinylketon zugänglich. Versuche, aus dem Enin X bzw. dem Tetrahydro‐diphenyl‐Derivat XIV durch Diensynthese in die Phenanthren‐Reihe zu gelangen, waren erfolglos.
Contribution à la phytochimie du genre Gentiana. VII. Etude des composés flavoniques et xanthoniques dans les feuilles de Gentiana vernaL. (1ère communication)
Authors: Hostettmann Kurt , Jacot‐Guillarmod André 
Published: December 2004

AbstractA new xanthone‐O‐glycoside, the 1,7‐dihydroxy‐3‐methoxyxanthone‐8‐O‐β‐D‐glucopyranoside (7), has been isolated from the leaves of Gentiana verna L. by means of column chromatography on polyamid. Six known xanthones: 1‐hydroxy‐3,7,8‐trimethoxyxanthone‐1‐O‐primerveroside (2); 1,7,8‐trihydroxy‐3‐methoxyxanthone (3); 7‐hydroxy‐3,8‐dimethoxyxanthone‐1‐O‐primeveroside (4); 7,8‐dihydroxy‐3‐methoxyxanthone‐1‐O‐primeveroside (5); mangiferin 6 and the flavone C‐glycoside isoorientin 8 have also been isolated and identified.
Etude par spectrométrie de masse des cyclopenténols, cyclopentène‐diols‐3,4 et cyclopentène‐triols‐3,4,5
Authors: Singy Gérard A. , Buchs Armand 
Published: December 2004

AbstractThe mass spectra of cyclopentene‐1‐ol‐3, ‐1‐o1‐4, those of cis‐ and trans‐cyclopentene‐3,4‐diol and of the three stereoisomers of cyclopentene‐3,4,5‐triol have been studied. Decomposition modes based upon results obtained using deuterium labelled analogues are discussed.
2‐Dialkylamino‐3,7‐dehydrotropone
Authors: Dahl Charles E. , Gray Robert W. , Dreiding André S. 
Published: December 2004

AbstractBehandlung des durch N‐Brom‐succinimid aus 7,7‐Dichlor‐bicyclo[3.2.0] hept‐2‐en‐6‐on erhaltenen 4‐exo‐Brom‐7,7‐dichlor‐bicyclo[3.2.0]hept‐2‐en‐6‐ons (1) mit Lithiumdiisopropylamid ergab 2‐Diisopropylamino‐3,7‐dehydrotropon (2). Auf gleiche Weise wurde mit Lithium‐dimethylamid das entsprechende 2‐Dimethylamino‐3,7‐dehydrotropon (3) hergestellt. Die Strukturen von 2 und 3 ergeben sich aus den Spektraleigenschaften, welche auch die starke π‐Elektronendelokalisierung im 2‐Amino‐dehydrotropon‐System widerspiegeln.
Azidiniumsalze. 10.Mitteilung [1]. Struktur‐Reaktivitäts‐Beziehungen in Serien quartärer N‐Heteroaromaten: Diazogruppen‐Übertragungsreaktion heterocyclischer Azidiniumsalze auf 1‐(p‐Sulfophenyl)‐3‐methylpyrazolin‐5‐on und 1‐(m‐Sulfophenyl)‐3‐methyl‐5‐amino‐pyrazol
Authors: Balli Heinz , Hellrung Bruno , Kneubühler‐Hof Annemarie 
Published: December 2004

AbstractEs wurde die Diazogruppen‐Übertragungsreaktion von Azidinumsalzen des Typs 1 auf 1‐(p‐Sulfophenyl)‐3‐methyl‐pyrazolin‐5‐on und 1‐(m‐Sulfophenyl)‐3‐methyl‐5‐amino‐pyrazol untersucht und die Geschwindigkeitskonstante der Reaktion in Abhängigkeit vom Heterocyclus des Azidiniumsalzes bestimmt. Die Geschwindigkeitskonstanten k1 zeigen untereinander und mit den aus den pK‐Werten der Iminoverbindungen 4 definierten σHet‐Werten [1] eine gute Korrelation in Form einer linearen Freien‐Energie‐Beziehung.
Synthesis of some Indanones having Nitrogen‐containing Substituents
Authors: Berney Daniel , Jauner Theodor 
Published: December 2004

AbstractThe title compounds have been synthesized by a Friedel‐Crafts acylation‐alkylation between aromatic ethers and α,β‐unsaturated carboxylic acids (or esters) having nitrogen‐containing substituents. Polyphosphoric acid was used as condensing agent.
Intramolekulare Diels‐Alder‐Additionen von 1,2‐Dihydropyridinen
Authors: Greuter Hans , Schmid Hans 
Published: December 2004

AbstractReduction of the pyridinium salts 1b‐f in methanolic sodium hydroxide solution with sodium borohydride gave the dimeric dihydropyridine derivatives 3b‐f. Heating these dimers in hydrocarbon solvents at 110–207° resulted in the formation of the tricyclic amines 4c–f, which were shown to be products of an intramolecular Diels‐Alder addition within the intermediate dihydropyridines 2c–f. The structures of 4c–f were deduced from spectroscopic, mainly NMR. data.
C(10)‐Methylation of Steroidal Synthesis Intermediate BCD‐Tricyclic 9‐En‐5‐ones
Authors: Scott John W. , Buchschacher Paul , Labler Ludwik , Meier Werner , Fürst Andor 
Published: December 2004

AbstractA literature survey indicated that stereospecific non‐reductive β‐face methylation at C(10) of steroidal synthesis intermediate BCD‐tricyclic 9‐en‐5‐ones had never been effected. An attempt to define the factors controlling the β/α product ratio in such alkylations was made. The course of methylation is significantly affected by the temperature. In the best case, methylation of the sodium enolate of 17 β‐t‐butoxy‐19‐(3,5‐dimethyl‐4‐isoxazolyl)‐deA‐androst‐9‐en‐5‐one (18) in tetrahydrofuran at − 78° gave a β/α product ratio of > 5:1. The reaction mixture contained no unalkylated or dialkylated materials, indicating that enolate exchange probably did not occur at this temperature. The 10β‐methylated product 23, isolated in 78% yield, was converted to Δ9(ll)‐dehydrotestosterone (29). Compounds 23 and 29 are potential intermediates for the synthesis of 11‐oxygenated steroids.
Darstellung und Eigenschaften von Chromtricarbonyl‐Komplexen strukturisomerer Borazin‐Derivate
Authors: Scotti Mario , Werner Helmut 
Published: December 2004

AbstractThe new hexaalkylborazine chromium tricarbonyls (n‐Pr)3B3N3Me3Cr(CO)3 (V), Me3B3N3(n‐Pr)3Cr(CO)3 (VI), (i‐Pr)3B3N3Me3Cr(CO)3 (VII) and Me3B3N3(i‐Pr)3Cr(CO)3 (VIII) have been prepared from fac‐Cr(CO)3(MeCN)3 and the corresponding borazine in dioxane or without solvent. They are much more labile than the isomeric complex Et3B3N3Et3Cr(CO)3 (IV) which can be readily obtained from Et3B3N3Me3Cr(CO)3 and Et3B3N3Et3 by ring ligand exchange. The NMR., IR., UV. and Mass spectroscopic data of the complexes IV–VIII will be briefly discussed. The preparation of the borazine derivatives (n‐Pr)3B3N3Me3 (IX) and Me3B3N3(n‐Pr)3 (X) is also reported.
Über Reaktionen oxygenierter Kobalt(II)‐Chelate. II. Konfigurationsisomere Oxygenierungsprodukte von Tetraäthylenpentaminkobalt(II)
Authors: Zehnder Margareta , Fallab Silvio 
Published: December 2004

AbstractOn oxygenation of alcoholic solutions of tetraethylenepentamine cobalt(II) two isomeric forms of [(tetren)CoO2Co(tetren)]4+ are obtained in which the configuration of the pentadentate ligand is either α or β. The binuclear complex can be crystallized as thiocyanate or as perchlorate. Oxygenation at 35° produces the pure α isomer. At lower temperature a mixture of α and β is obtained. The isomers differ slightly in their absorption spectra and their reactivity. The ligand configuration has been elucidated by transforming the perchlorates into the [ZnCl4]2− salts of the corresponding mononuclear chelates [Co(tetren)Cl]2+. The latter have also been prepared starting from a compound of known configuration according to the literature. The IR. spectra of the α and β forms differ characteristically in the NH stretch bands.
Substituent Increments for the 1H‐NMR. Chemical Shifts of the 18‐ and 19‐Methyl Protons of Steroids. Part II: 9α,10β(normal)‐steroids
Authors: Arnold Wolf , Meister Walter , Englert Gerhard 
Published: December 2004

AbstractIn Part II of this series we report 292 substituent increments for the 1H‐NMR. chemical shifts (solvent: CDCl3) of the 18‐ and 19‐methyl protons of 9α,10β(normal)‐steroids relative to 5α,9α,10β,‐androstane. The increments were calculated by a least‐squares procedure from 988 spectra of 681 different steroids.
Hormone‐Receptor Interactions. Synthesis of a biologically active cysteinyl‐angiotensin derivative and its use for the preparation of spin‐labelled and polymer‐supported molecules
Authors: Möschler Hans Jörg , Schwyzer Robert 
Published: December 2004

Abstract(N‐t‐Butoxycarbonyl‐S‐acetamido‐methyl‐L‐cysteinyl)‐[1‐ asparagine, 5‐valine]‐angiotensin II (2) was prepared from [1‐asparagine, 5‐valine]‥angiotensin II (1). With respect to enhancement of rat blood pressure, it is a full agonist displaying about 20–25% of the potency of 1. The sulfur atom of the cysteine group represents a specific nucleophile by which the hormone can easily be attached to other molecules in a well‐defined manner. Thus, 2 has been added to N‐substituted maleimides through its (deprotected) thiol group to produce the spin‐labelled derivative 3:{N‐t‐butoxy‐carbonyl‐S‐[N‐(1‐oxy‐2,2,5,5‐tetramethyl‐ pyrrolidin‐3‐yl‐methyl)‐imidosuccin‐3‐yl]‐L‐cysteinyl}‐[1‐asparagine,5‐valine]‐angiotensin II, and the polymer‐supported derivative 6: S‐(N‐{5‐[7‐(sepharosyl‐oxy‐carbonimidoyl‐amino)‐4‐azaheptylcarbamoyl]‐pentyl}‐imidosuccin‐3‐yl)‐L‐cysteinyl‐[1‐asparagine, 5‐valine]‐angiotensin II. The ESR. spectra of 3 in different solvents, and its principal NMR. characteristics, are reported. We are using the compound for studying its interaction with receptor molecules and for purification of target cells and membrane vesicles by affinity aggregation.
Thermische Umlagerung von Propargyloxy‐cycloheptatrien‐Derivaten
Authors: Pryde Andrew , Zsindely Janos , Schmid Hans 
Published: December 2004

AbstractThe thermal rearrangement of 7‐propargyloxy‐cycloheptatriene in decane solution at 180°C gave bicyclo[3.3.2]deca‐3,7,9‐trien‐2‐one (13) and the unstable 2,7‐dihydro‐cyclohepta[b]‐pyran (12) (Scheme 2). The structures of these compounds were determined mainly by NMR. spectroscopy. Derivatives of 13 were also identified by comparison with known compounds (Scheme 3). Possible mechanisms for the formation of 13 and 12 are outlined in Schemes 5 and 6 respectively.The thermal rearrangement of 2‐propargyloxy‐cycloheptatrienone (21) gave, in high yield, 2‐methyl‐8H‐cyclohepta[b]furan‐8‐one (22) (Scheme 7).