bluuebunny/crossref_metadata_2025 huggingface dataset:
C‐Glycosides VI. Modalités de l'élaboration de cycles pyrazoliques à partir d'une hydrazone d'aldéhydo‐sucre
Authors: Tronchet J. M. J. , Jotterand A.
Published: December 2004

The reaction of an aldehydo‐sugar hydrazonoyl bromide with ethynylmagnesium bromide led mainly to an α‐ethynyl‐hydrazone whose cyclisation to a pyrazole is catalysed by bases. Thus the nucleophilic substitution – nucleophilic cyclisation mechanism of the Grünangerpyrazole synthesis is confirmed. 3‐Glycosyl‐pyrazoles can also be prepared from aldehydo‐sugar hydrazonoyl bromides by 1,3‐dipolar cyclo‐addition. All these reactions take place without change in the configuration of the initial aldehydo‐sugar.
A Semi‐Empirical Model of the Energy Barrier of Proton Transfer Reactions
Authors: Willi Alfred V.
Published: December 2004

The energy barrier in proton transfer reactions is described by a Johnston‐type equation (1) (n = order of bond to be broken). The barrier model is discussed in terms of free energies. The Vi values are free energies of ionic cleavage in aqueous solution of the XH and YH bonds; they are computed from eqns. (4c) and (4d). The values of p1 and p2 affect curvature (absence or presence of maximum) and symmetry of the barrier. It is postulated that pi is a typical constant of the reacting bond and can be transferred from one transition state to another.

With the aid of eqn. (1) and its first derivative, values of pi and nm (bond order at maximum of barrier) can be based on quantities determined experimentally, Δ≠ and ΔG. For OH bonds, pi ≈ 1.0. For CH bonds pi is larger than 1.0 and depends on the structure of the carbanionic moiety (influence of resonance and inductive effects).

As there cannot be a maximum if p1 = p2 = 1.0, the suggested model of the barrier leads to a better understanding why proton transfer must be ‘fast’ in some reactions and ‘slow’ in others. The computed values of nm may be utilized to gain some insight into the nature of the transition states; they supply a basis for the discussion of primary hydrogen isotope effects.
Réactions de substitution dans l'anion tétrachloropalladate(II) avec des diamines. I. Ethylènediamine
Authors: Roulet R. , Ernst R.
Published: December 2004

The replacement of Cl− by ethylenediamine (en) in PdCl has been followed spectrophotometrically at 25°C and μ = 1 (NaClO4); it proceeds in two steps leading to Pd(en)Cl2 and Pd(en), respectively. The observed rate constants are discussed in terms of the mechanism proposed by Reinhardt [1] for the successive ammination reactions of PdCl.
Etude de composés d'addition d'acides de Lewis. XXXVI [1] Composés d'addition de l'anthraquinone‐9, 10 et de l'anthrone avec divers acides de Lewis
Authors: Giallonardo R. , Susz Bernard‐P.
Published: December 2004

Solid stoichiometric adducts of 9, 10‐anthraquinone with SbCl5, ZrCl4, TiCl4 SnCl4, AlCl3, have been prepared. The very important lowering Δω of the IR. carbonyl frequency, ranging from −175 cm−1 for SbCl5 to −117 cm−1 for SnCl4, shows that the acceptor is linked by a dative bond to the carbonyl oxygen atom acting as a donor; an assignment of most of the fundamental IR. frequencies is proposed for anthraquinone and the mentioned adducts.

Similar assignments and interpretation have been made for anthrone and its solid adduct with SbCl5, ZrCl4, TiCl4, SnCl4, AlCl3 and ZnCl2, where the CO lowerings range from −164 cm−1 for SbCl5 to −97 cm−1 for ZnCl2.
Die Aminoalkylierung von Chinoxalinen und Chinoxalonen 6. Mitteilung über grignard‐reaktionen mit halogenalkylaminen [1]
Authors: Marxer A. , Salzmann U. , Hofer F.
Published: December 2004

Quinoxaline and 2(1H)‐quinoxalones react with organomagnesium salts differently from the corresponding phthalazines and quinazolines. 3‐Dimethylaminopropyl‐magnesiumchloride alkylates quinoxaline easily by addition to the 2 and 3 position forming a tetrahydroquinoxaline 2, which can be dehydrogenated to the corresponding dialkylated quinoxaline 3. The monosubstituted dihydroquinoxaline 5 is obtained only with difficulty. It can equally be dehydrogenated, yielding 6.

Quinoxalones react with CH3MgI, C6H5MgBr, (CH3)2N(CH2)3MgCl by addition to the 3,4‐CN bond (not at the CO‐group), yielding 11–13. These dihydroquinoxalones are dehydrogenated to the 3‐substituted 2(1H)‐quinoxalones 14–16. Only 3‐phenyl‐quinoxalone adds a Grignard reagent at the CO group, forming a 2‐substituted 3‐phenylquinoxaline (26). 3‐Methyl‐quinoxalone exhibits an abnormal behaviour: It is deprotonated by the mentioned reagents at the CH3 group, and the 3‐methylenequinoxalone‐anion so formed attacks another molecule of methylquinoxalone, finally yielding 32 and 33.
L'action de l'ammoniac sur l'hydroxyde de cadmium et la stabilité des complexes en milieu aqueux
Authors: Gübeli A. O. , Taillon R.
Published: December 2004

The solubility of precipitated Cd(OH)2 was determined at 25°C in 1 M NaClO4, as a function of pH and of the ammonia content of the solutions. Formation constants were obtained for the following hydroxo, ammine and hydroxo‐ammine complexes: CdOH+, Cd(OH)2, Cd(OH), CdNH, Cd(NH3), Cd(NH3), Cd(NH3) and Cd(OH)2NH3. The solubility product of the hydroxide was also calculated.

The presence of polynuclear species was investigated by titrimetric determinations of the hydrogen ion concentration at constant metal concentration.
Lävulinsäureanilid und 5‐Hydroxy‐5‐methyl‐1‐phenyl‐2‐pyrrolidon
Authors: Keller O. , Prelog V.
Published: December 2004

The hitherto unknown tautomer of levulinic acid anilide (Ia), 5‐hydroxy‐5‐methyl‐1‐phenyl‐2‐pyrrolidone (IIa), has been obtained by filtration of a chloroform solution of I a through acid ion‐exchange columns. Ia and IIa show typical differences in NMR., IR. and MS. that can be used for their detection and determination in mixtures. Both tautomers are stable at room temperature in solid state and in neutral solutions but are equilibrated in acidic and basic solutions.
Valenzisomerisierung von cis‐Dienonen, III Lichtinduzierte Umlagerung von 5‐Phenyl‐penta‐2,4‐dienaldehyden [1]
Authors: Schiess P. , Suter ChR.
Published: December 2004

Irradiation of 5‐phenyl‐2,4‐pentadienaldehydes 1 and 2 leads to a rapid cis, trans‐isomerization of the 4,5‐double bond followed by formation of unsaturated ketenes 7 and 12, respectively, through a [1.5]‐hydrogen shift. In the dark, ketenes 7 and 12 revert at room temperature to the 5‐phenyl‐2,4‐pentadienaldehydes 1 und 2. Activation parameters and solvent dependence have been determined for this remarkably facile [1.5]‐sigmatropic rearrangement. The ketenes 7 and 12 are stable below − 20° in inert solvents. With alcohols and amines mixtures of α,β‐ and β,γ‐unsaturated acid derivatives are formed. Upon extended irradiation of 7 and 12 in aprotic solvents olefins 9 and 13 are formed through decarbonylation.
Human Milk Lysozyme: Unpublished Data Concerning the Establishment of the Complete Primary Structure; comparison with lysozymes of various origins
Authors: Jollès Jacqueline , Jollès Pierre
Published: December 2004

Details concerning the establishment of the complete primary structure of human milk lysozyme (previously published in a preliminary note) are presented. The chymotryptic peptides obtained from the reduced alkylated enzyme were purified and their amino acid sequences determined chiefly by the ‘Edman‐dansylation’; procedure, and in two cases by partial acid or peptic hydrolyses. The tryptic peptides are alined into a single chain containing 129 amino acid residues, on the basis of overlapping peptides. Two labile glutamine residues easily converted into glutamic acid residues were characterized. Human milk lysozyme is compared with other human lysozymes (from normal and leuchaemic individuals) prepared by our group. The structure proposed is identical with the sequence of human leuchaemia lysozyme (from the urine of a patient with chronic monocytic leuchaemia) reported by Canfield. Human milk lysozyme is also near by related to several bird egg‐white lysozymes (and bovine α‐lactalbumin): Identical positions of Cys and Trp residues and of the residues essential for the catalytic activity or involved in some hydrogen bonds; several identical regions, especially in the β‐sheet region; between 71 and 77 identical amino acid residues. It is suggested that by an insertion and a deletion in the sequence of human milk lysozyme, sequences homologous to those of bird lysozymes can be obtained.
Zur säurekatalysierten Cyclisation von Verbindungen der Damascenon‐Reihe
Authors: Ohloff G. , Schulte‐Elte K. H. , Demole E.
Published: December 2004

The acid catalyzed cyclisation of α‐ and β‐diamascone (4 and 1) as well as β‐damascenone (2) has been examined under different conditions. The reaction mechanism is discussed.
Strukturaufklärung zweier Pigmentfarbstoffe der Perylen‐Reihe
Authors: Manukian B. K. , Mangini A.
Published: December 2004

The structures of C.I. Pigment Red 149 (PV Fast Red B)® and C.I. Pigment Red 178 (Paliogen Red GG)® as II and III respectively, are deduced from elemental analysis, spectroscopic data, and synthesis.
Reaktionen von Steroid‐Hypojoditen X. Fragmentierung von 20‐Hydroxy‐Steroiden (17‐Jod‐androstane). Über Steroide, 226. Mitteilung
Authors: Biollaz M. , Kalvoda J.
Published: December 2004

In the hypoiodite reaction of 20‐hydroxy steroids, 17α‐ and 17β‐iodo androstanes are formed as by‐products by fragmentation of the intermediate alkoxy radicals. The epimeric iodides show antipodal CD.‐ and ORD.‐ curves in accordance with their absolute configuration at the relevant chiral centre C(17).
Die Kristallstruktur des 3β‐Acetoxy‐17α‐jod‐Δ5‐androstens
Authors: Mez H.‐C. , Rihs G.
Published: December 2004

The crystal structure of 3β‐acetoxy‐17α‐iodo‐Δ5‐androstene (C21H31O2I) has been determined from three‐dimensional X‐ray data and refined to a final reliability index of R = 5.1% for the 2352 observed reflexions. Crystals grown from methylene chloride/methanol are orthorhombic, space group P212121, with cell constants a = 6.430, b = 10.563, c = 29.369 Å.
Eine neue Amidinsynthese mit Hilfe der Grignard‐Reaktion. 7. Mitteilung über Grignard‐Reaktionen [1]
Authors: Marxer A.
Published: December 2004

In an unusual manner benzonitrile 5 and the substituted benzonitriles 1, 14 reacted with benzylmagnesiumhalides to yield, besides dibenzyl, the amidines 7, 13, 15, substituted on the imide nitrogen by a 1,2‐diphenyl‐vinyl group. The proposed structures are based on NMR. and mass spectra.
Stoffwechselprodukte von Mikroorganismen. 104. Mitteilung [1]. Die Struktur des Cinerubins B.
Authors: Richle W. , Winkler E. K. , Hawley D. M. , Dobler M. , Keller‐Schierlein W.
Published: December 2004

The structural determination of the anthracycline antibiotic Cinerubine B by degradation, spectroscopic studies and an X‐ray crystallographic analysis of a degradation product is described.
The Crystal and Molecular Structures of an Unusual Estra‐Steroid and of its Dihydroproduct
Authors: Weber H. P. , Galantay E.
Published: December 2004

The crystal and molecular structures of 17‐ethylenedioxy‐3‐methoxy‐6,7,8‐methylidyne‐1,3,5(10)‐estratriene (1) and of 17β‐bromo‐acetoxy‐3‐methoxy‐8α‐methyl‐1,3,5(10),6‐estratetraene (3) have been determined by X‐ray analysis. A short discussion of the structures is given, and a new picture of the structure‐activity relation of estrogenics is proposed.
Utilisation d'ylides du phosphore en chimie des sucres, X. Synthèse stéréospécifique de l'épimère en C3 du streptose et d'autres sucres ramifiés, dérivés de désoxy‐5‐pentoses, à groupements gem‐hydroxy‐formyle ou gem‐hydroxy‐hydroxyméthyle
Authors: Tronchet J. M. J. , Graf R. , Gurny R.
Published: December 2004

The synthesis of branched‐chain sugars of the gem‐hydroxy‐formyl and the gem‐hydroxy‐hydroxymethyl types is described. A 5‐deoxy‐1,2‐O‐isopropylidene‐furanos‐3‐ulose is treated with cyanomethylene‐triphenyl‐phosphorane, yielding the two geometrical isomers of the corresponding branched‐chain unsaturated sugar. Cis‐dihydroxylation(KMnO4) of these cyanomethylenic compounds affords stereoselectively and in high yield the gem‐hydroxy‐formyl branched chain sugars whose formyl group is on the more hindered face of the furanose ring. The hydroxymethyl analogues of the latter compounds are readily prepared by their borohydride reduction. This method constitutes a new general route to type A branched‐chain sugars epimeric at the branching‐point with the sugars which would have been obtained by the classical procedure involving Grignard reagents.
Stereochemical Assignment of the Two Isomeric Tropine N‐Oxides by Proton Magnetic Resonance at 220 MHz
Authors: Bachmann K. , von Philipsborn W.
Published: December 2004

Proton magnetic resonance spectra of tropine and the two isomeric tropine N‐oxides have been analysed at 220 MHz. Chemical shifts in the N‐oxides are expressed relative to tropine (Δv) and permit unequivocal structural assignments of the predominant isomer (1, equatorial N‐oxide) and the minor isomer (2).
The Reaction of Phenyl(trichloromethyl)mercury with Substituted Norbornenes
Authors: Jefford C. W. , Hill D. T. , Goré J. , Waegell B.
Published: December 2004

The addition of phenyl(trichloromethyl)mercury to five substituted norbornenes is described, and the results compared with those obtained with bicyclo[2.2.2]oct‐2‐ene and 3,3,5,5‐tetramethylcyclopentene. The reaction proves to be useful for synthetic purposes, in that it leads usually to ring expansion. However, a possible disadvantage is that the addition step is sensitive to steric hindrance and depends on the reactivity of the double bond.
Anil‐Synthese. 6. Mitteilung. Über die basenkatalysierte Umsetzung von methylsubstituierten 2H‐Naphtho[1,2‐d]triazol‐2‐yl‐benzolen und ‐naphthalinen mit Anilen aromatischer Aldehyde
Authors: Brunold M. , Siegrist A. E.
Published: December 2004

Methylgruppen in verschiedenen Stellungen des Benzolringes von 2H‐Naphtho[1,2‐d]triazol‐2‐yl‐benzol können mit Anilen aromatischer Aldehyde in Dimethylformamid in Gegenwart von Kaliumhydroxid in Styrylgruppen übergeführt werden («Anil‐Synthese»). Der Einfluss von Substituenten in Nachbarstellung zur Methylgruppe von 2‐(p‐Tolyl)‐2H‐naphtho[1, 2‐d]triazol auf den Reaktionsablauf wird untersucht. Aus 2‐Fluor‐4‐(2H‐naphtho[1, 2‐d]‐triazol‐2‐yl)‐toluol und Anilen aromatischer Aldehyde entstehen in Dimethylformamid in Gegenwart von Kaliumhydroxid 1,2,3‐Triphenyl‐7‐(2H‐naphtho[1, 2‐d]triazol‐2‐yl)‐1,4‐dihydrochinolin‐Derivate.
Synthese der 2,5‐Diole des A‐nor‐5α‐Androstan‐17β‐ols und A‐nor‐5β‐Androstan‐17β‐ols
Authors: Lábler L. , Tamm Ch.
Published: December 2004

The synthesis of A‐nor‐5β‐androstane‐2α,5,17β‐triol (8), A‐nor‐5β‐androstane‐2β,5,17β‐triol (10), A‐nor‐5α‐androstane‐2β,5,17β‐triol (20), A‐nor‐5α‐androstane‐2β,5,17β‐triol (22) and of their 17‐O‐benzoyl derivatives is described, using A‐nor‐testosterone (1) as starting material.
Orbital Theory of Heterolytic Fragmentation and Remote Effects on Nitrogen Inversion Equilibria
Authors: Gleiter Rolf , Stohrer Wolf‐Dieter , Hoffmann Roald
Published: December 2004

From a molecular orbital study of model systems we derive the electronic requirements for the Grob fragmentation. The necessary condition for an allowed fragmentation in an X‐C1‐C2‐C3‐N system, or the amino cation +C1‐C2‐C3‐N is the level ordering A below S. This in turn is set by maximal through‐bond coupling of the empty cation orbital and the nitrogen lone pair. The conformational dependence of through‐bond coupling is exactly that derived by Grob, namely parallel orientation of the cation orbital (or the C‐X bond), the C2‐C3‐σ‐bond, and the N‐lone‐pair. When the C1‐C2‐C3 and C2‐C3‐N angles are small, the through‐space interaction dominates, reversing the level ordering to S below A, and consequently makes the fragmentation forbidden even though the conformational requirements for it are met. Ring closure becomes allowed. Some examples exploiting this result are presented, as well as procedures for enhancing through‐bond coupling and thus fragmentation. The through‐bond‐effect has also kinetic consequences, allowing the definition of a new type of remote neighbouring group participation operative through bonds and not by direct overlap. The position of equilibria in nitrogen inversion processes should also be influenced by remote substituents which are π‐acceptors or donors.
Addition von Phthalidnatrium an 2‐Carbäthoxy‐8‐methoxynaphthochinon; eine neue Synthese für Hydroxy‐naphtacenchinone
Authors: Trueb W. , Eugster C. H.
Published: December 2004

A simple method to synthesize hydroxysubstituted naphthacenequinones is described. Phthalide anion adds to negatively substituted quinones, e.g. ethyl‐8‐methoxy‐naphthatquinone‐2‐carboxylate. Acid catalysed cyclisation of this adduct under simultaneous decarboxylation yields a substituted naphthacene quinone.
Isolierung, Struktur und Synthese des Metaboliten von Azapropazon‐dihydrat
Authors: Mixich G.
Published: December 2004

The renal excretion of AZAPROPAZONE‐DIHYDRATE (X)

Handelsname: PROLIXAN®. Hersteller: Siegfried AG, Zofingen.

by humans was investigated. Following oral administration a new substance was detected in the urine besides X by TLC. Both compounds were separated by preparative layer chromatography and shown to be unchanged X and its hydroxylated metabolite VIII. The structure of VIII was established by chemical and spectroscopic methods (IR., NMR.) and confirmed by synthesis (Scheme 1).
Fluorénacènes et fluorénaphènes Synthèses dans la série des indéno‐fluorènes, XVI. Méthyl‐5‐, diméthyl‐5, 6‐ et diphényl‐5, 6‐dihydro‐11, 12‐indéno [2.1‐a] fluorène
Authors: Chardonnens Louis , Bitsch Serge
Published: December 2004

Starting from 2‐methyl‐ and from 2,3‐dimethyl‐1,4‐diphenyl‐butadiene‐1, 3 respectively, the 5‐methyl‐ and the 5,6‐dimethyl‐11, 12‐dihydro‐indeno[2.1‐a]fluorene are synthesized in 4 steps. The 5, 6‐diphenyl‐11, 12‐dihydro‐indeno[2.1‐a]fluorene is obtained by reduction of the already known 11, 12‐dioxoderivative. Accesorily a new preparation of the unsubstituted hydrocarbon is described.
Steroide und Sexualhormone. 244. Mitteilung. Synthese der C‐20 epimeren 7,8‐Dihydrobatrachotoxinine
Authors: Graf W. , Gössinger Frl. E. , Imhof R. , Wehrli H.
Published: December 2004

A novel synthesis leading to the C(20) epimeric 7,8‐dihydroderivatives 16 [1] and 34 of batrachotoxinin A (1) [5] is described.
The Relationship between C6H5N Isomers. Pyrolysis of isatins
Authors: Wentrup Curt
Published: December 2004

The pyrolysis of methyl isatins is described. Examination of the toluidines formed by elimination of 2 CO followed by H‐abstraction indicates that 1H‐benzazirines (12) are inter‐mediates. The interconversion of 1H‐ and 1aH‐benzazirine (15) is not detectable. 1‐Phenyl‐benzotriazole does not give a benzazirine intermediate.
Die vermutliche Struktur der Anodendroside. Glykoside und Aglykone, 331. Mitteilung
Authors: Lichti H. , von Euw J. , Stöckel K. , Polonia J. , Reichstein T.
Published: December 2004

Five crystalline compounds (anodendrosides) have been isolated from Anodendron paniculatum (Roxb.)A. DC. (Apocynaceae). They represent glycosides containing unusual sugars. Tentative structures for anodendroside‐A (155), −E1 (3), −E2 (84), −F (144) and −G (115) are now presented. These structures are based on UV., IR., but mostly on high resolution mass spectra. NMR.‐spectra could be performed with A, O‐acetyl‐E2 and O‐acetyl‐G, which are in good agreement with the suggested structures. The unusual methylendioxy group postulated in the sugar moiety of A, E1 and E2 was also established by chemical methods, yielding approximately 1 Mol. equiv. of formaldehyde after acid hydrolysis of anodendroside‐E2.
Coleon D, ein Diterpen aus Coleus aquaticus Guercke mit trans‐A/B‐6,7‐Dioxostruktur
Authors: Rüedi P. , Eugster C. H.
Published: December 2004

Coleon D, C20H26O6 a new orange red diterpenoid hydroquinone has been isolated from the yellow glands on the leaves and inflorescences of Coleus aquaticus Guercke (Labiatae). Its structure has been determined as 11,12,14,16‐tetrahydroxy‐5α‐abieta‐8,11,13‐trien‐6,7‐dion (1) Therefore it is a tautomer of Coleon C (2). Coleon D is the precursor of Coleon C.
Nachweis von Desacetylakuammilin und 10‐Methoxy‐desacetylakuammilin in Vinca minor L. 147. Mitteilung über Alkaloide
Authors: Savaskan S. , Kompiš I. , Hesse M. , Schmid H.
Published: December 2004

The two indole alkaloids desacetylakuammiline (2) and 10‐methoxy‐desacetylakuammiline (4) were shown to occure in the upper parts of the small periwinkel Vinca minor L. The structure of the hitherto unknown 10‐methoxy‐desacetylakuammiline was established on the bases of chemical, spectroscopic and o.r.d. evidence.
Composés d'addition des halogénures de niobium(V) et de tantale(V). VII. Composés du chlorure de niobium(V) avec l'oxytrichlorure et l'oxytribromure de phosphore
Authors: Bünzli J. C. , Merbach A.
Published: December 2004

The adducts NbCl5 · OPCl3 and NbCl5 · OPBr3 are observed in chloroform solution by 31P‐NMR spectroscopy. The enthalpy and entropy of activation for the exchange reaction between bulk and coordinated OPCl3 are found equal to 17 ± 3 kcal/mole and 18 ± 10 cal/°mole. The stability of NbCl5 · OPCl3 is compared on a semi‐quantitative basis to the stability of other adducts NbCl5 · OPR3 (R = Br, OMe, NMe2).
Anil‐Synthese. 8. Mitteilung. Über die basenkatalysierte Umsetzung von 2‐(p‐Tolyl)‐7‐aryl‐benzo[1, 2‐d:3, 4‐d′]bis‐triazolen mit Anilen aromatischer Aldehyde
Authors: Siegrist A. E.
Published: December 2004

2‐(p‐Tolyl)‐7‐aryl‐benzo[1, 2‐d:3, 4‐d′]bis‐triazole und 2, 7‐Di‐(p‐tolyl)‐benzo[1′2‐d:3, 4‐d′]bis‐triazole können mit Anilen aromatischer Aldehyde in Gegenwart von Dimethylformamid und Kaliumhydroxid in 2‐(Stilben‐4‐yl)‐7‐aryl‐ bzw. 2, 7‐Di‐(stilben‐4‐yl)‐benzo[1′2‐d:3, 4‐d′]bis‐triazole übergeführt werden («Anil‐Synthese»).
Ein neuer Süßstoff aus der Indolreihe
Authors: Hofmann A.
Published: December 2004

The synthesis of 3, 4‐dehydro‐2‐(3‐indolylmethyl)‐1‐methyl‐piperidine‐4‐carboxylic acid, a new dulcifiant of the indole series being twice as sweet as saccharine, is described.
Ein Kobalt(II)‐Corrin‐Komplex als reversibler Sauerstoffträger. Eine ESR.‐spektroskopische Untersuchung
Authors: von Zelewsky A.
Published: December 2004

The diamagnetic crystalline Jodo‐Co(II)‐cobyrinicacid‐heptamethylester dissolves in benzene or toluene forming solutions which contain the monomeric paramagnetic complex unit. From anisotropic ESR.‐parameters, measured in frozen solutions, follows a ground state configuration (dxz,dyz)4(dxy)2(dz2)1 for the Co(II). The unpaired electron is highly delocalized to the axially coordinated iodide ion, giving rise to a strong hyperfine coupling with the iodine nucleus. The complex forms in a very fast and completely reversible reaction a 1:1 adduct with molecular oxygen in toluene solutions below ca. 280° K. ESR.‐parameters of the oxygen adduct are presented and discussed. Thermodynamic data for the formation reaction of the adduct are estimated.
Extraction liquide‐liquide par des esters alkylphosphoriques. I. Extraction de l'yttrium par l'acide di‐(2‐éthylhexyl)phosphorique
Authors: Brunisholz G. , Hirsbrunner W. , Roulet R.
Published: December 2004

The extraction of macro‐amounts of Yttrium from solutions of nitric and perchloric acids by di‐(2‐ethylhexyl)phosphoric acid has been studied. The extraction of Yttrium is more effective from the perchloric medium and takes place by two mechanisms: an ion‐exchange reaction Y3+/H+ at low concentrations and a solvatation reaction at high concentrations of Yttrium. The stability constant of the mononitratocomplex YNO has been estimated.
Ringerweiterung in organischen Molekeln unter Elektronenbeschuss: Die massenspektrometrische Fragmentierung von 2,3‐dicarbalkoxy‐spiro‐cyclopropan‐1, 9′‐fluorenen
Authors: Richter Wilhelm J. , Braun André M.
Published: December 2004

Ring Expansion of a three‐ to a five‐membered cyclic structure in conjunction with loss of a carbalkoxy radical from the molecular ions is postulated for a series of 2,3‐dicarbal‐koxy‐spiro‐cyclopropane‐1,9′‐fluorenes. Initial rupture of the strained spiro‐cyclopropane system with destruction of the distinct molecular geometry is inferred from virtually identical spectral patterns of, cis‐ and trans‐isomers, whereas reclosure of the ‘open’ intermediate to a cyclopentadiene ring can be deduced from the secondary decomposition of the resulting (M–COOR) fragments. These latter ions exhibit loss of the second carbalkoxy group together with a hydrogen atom of unusual positional origin (1′ or its equivalent 8′) to form a pair of neutral species, ROH and CO. Since the ejection of hydrogen from aromatic positions can be taken as evidence of rearomatisation in the course of substitution, this origin is liable to mark the site of the new ring junction and thus to reflect the size of the enlarged cyclic moiety.
Thermische Zerfallsreaktionen von Nitroverbindungen in Stosswellen. II: Dissoziation von Nitroäthan
Authors: Glänzer Klaus , Troe Jürgen
Published: December 2004

A shock wave study of the thermal decomposition of nitroethane in excess Ar at temperatures 900 < T < 1350 K and total concentrations of 4,5 · 10−6 < [Ar] < 3 · 10−4 mol cm−3 showed that the CN‐bond fission

is the primary reaction step. This unimolecular reaction could be observed in its transition region near the high pressure limit. The derived rate constants are k∞ = 1015.9 exp (–57 kcal mol−1/RT) s−1 for the high pressure and k0/[Ar] = 1018.0 exp (‐36 kcal mol−1/RT) cm3 mol−1 s−1 (at T ≃ 1100–1200 K) for the low pressure limit.

The observed concentration profiles of C2H5NO2 and NO2 permitted to conclude on the subsequent decomposition of the ethyl radical

This reaction was found to be in the fall‐off range under the applied conditions.
Aktivierungsanalytische Bestimmung von Spurenelementen in Blei durch Computerauswertung der Ge(Li)‐γ‐Spektren
Authors: Schubiger August , Wyttenbach Armin
Published: December 2004

Die aktivierungsanalytische Bestimmung von Spurenelementen in Blei durch Computerauswertung der Ge(Li)‐Spektren ergibt gute und reproduzierbare Resultate. Das entwickelte Verfahren ist sehr allgemein und schnell und lässt sich auch auf andere Probleme anwenden.
cis‐trans Isomerization of bis(Dialkylsulfide)Dihaloplatinum(II) Complexes in Solution
Authors: Roulet Raymond , Barbey Claude
Published: December 2004

The equilibrium energetics and the kinetics of cis‐trans isomerization of some bis(dialkylsulfide)dihaloplatinum(II) complexes have been examined by 1H‐NMR. spectroscopy. The isomers are stable in chloroform but each form isomerizes to an equilibrium mixture when free dialkylsulfide is added. The cis to trans process is endothermic and the position of the equilibrium is markedly dependent on the nature of the donor atoms and of the solvent. The rate of isomerization of Pt(Me2S)2Cl2 is first order in complex and in Me2S. The isomerization proceeds by a double displacement mechanism as it is shown that the tris(dimethylsulfide)chloroplatinum(II) cation is an isolable intermediate of the reaction. When free Me2S is added to trans‐Pd(Me2S)2Cl2, isomerization does not occur and one observes instead a fast ligand exchange. Its mechanism is the usual associative one for substitutions in square planar d8complexes.
Photoreduktion von 2‐phenylchinoxalin mit Alkoholen und Aminen
Authors: Baumann Niklaus
Published: December 2004

A mechanistic and kinetic analysis of the photoreduction of 2‐phenylquinoxaline (I) to 3‐phenyl‐1,2‐dihydroquinoxaline (II) in the presence of alcohols and amines is described. It is concluded that the reduction in alcohols proceeds exclusivly over an excited singlet state I (S1), probably of mixed n‐π*, π‐π* configuration. The triplet state which is also populated (ϕ;isc = 0.62) shows π‐π* configuration but remains inactive. A calculated pKa* 6.2 of I (S1) by means of a. Förster‐cycle, makes a mechanism which includes a first step photoprotonation of I (S1), followed by formation of semiquinone type radicals very probable.

In the presence of amines the formation of II proceeds exclusively via the first excited triplet state of I. The calculated rate constants are strongly dependent on the solvent polarity and on the ionisation potentials of the amines. This demonstrates clearly the importance of a charge‐transfer mechanism. It is also shown that once the charge‐transfer from the amine to I (T1) has occurred, physical quenching by electron backtransfer is of no importance. At high amine concentration I (S1)‐quenching is observed.
Oxidation – Reduction Reactions of Tetrachloroaurate(III) Anion with Triphenyl Derivatives of Group V Elements
Authors: Roulet Raymond , Lan Nguyen Quang , Mason W. Roy , Fenske Gerald P.
Published: December 2004

The reduction of the tetrachloroaurate (III) anion by L (L = PPh3, AsPh3, SbPh3) is quantitative in non‐aqueous solution. The products are the gold(I)‐complexes AuClL (L = AsPh3, SbPh3) and Au(PPh3)+2 together with the corresponding oxidation product LCl2. Kinetic studies show that the reactions are first order in AuCl−1 and L. In addition a path independent of PPh3 was found in dichloromethane. These data are interpreted in terms of mechanisms which involve reduction of AuCl−4 to AuCl−2 followed by equilibrium formation of AuClL for L = AsPh3 and SbPh3. For PPh3, the data are consistent with a chloride replacement by PPh3 to give AuCl3 PPh3, which is followed by a rapid reduction by a second mole of PPh3. Equilibrium formation constants are reported for several Au(I) complexes.
Über die spektrale Sensibilisierung von Zinkoxid: II. Anomales Sorptionsverhalten von o, o′‐Dihydroxyazofarbstoffen und Entladungskinetik des damit sensibilisierten Zinkoxids
Authors: Baumeler Rudolf , Rys Paul , Zollinger Heinrich
Published: December 2004

The first acidity constants (pK1) and the zinc complex formation constants (pKzn) of 9 dyes of the type 1‐(2‐hydroxy‐4′‐X‐5′‐Y‐phenylazo)‐2‐naphthol 1 were measured potentiometrically. The sorption behaviour of these dyes on zinc oxide in toluene demonstrates that first a Langmuir‐type pseudo‐equilibrium of the dye with a monomolecular edge‐on adsorption (11) can be observed. The more acidic the dyes, the more is this equilibrium disguised by a faster dissolution of zinc ions from the surface to form (practically irreversibly) the polymeric 1:1 zinc‐dye complex 10. This complex is detectable in electron micrographs. The discharge kinetics of dye‐sensitized zinc oxide‐binder layers in the dark and under irradiation by visible light (10 interference filters) was determined. Substituents X and Y have no detectable influence on the intrinsic discharge kinetics; however, they influence the formation of the polymer complex 10 which is contrast to 11 is not a good sensitizer.
Controlled Allylic Transformations via the Meisenheimer Rearrangement
Authors: Rautenstrauch Valentin
Published: December 2004

Described are synthetic sequences which effect allylic transformations I and II. Sequence I involves (1) conversion of a primary allyl alcohol into the corresponding N, N‐dimethyl‐amine oxide, (2) [2,3]‐rearrangement to give an N, N‐dimethylhydroxylamine and (3a) reduction to give the ‘rearranged’ secondary or tertiary allyl alcohol [e.g. 36 → 35 → 37 → 40]. Sequence II involves the same steps (1) and (2), followed by (3b) N‐methylation of a secondary N, N‐dimethyl‐hydroxylamine and (4) Hofmann elimination to give a vinyl ketone [e.g. 11 → 12 → 13 → 14 → 15].
Surface Chemistry of Polymers the Influence of Thermal and Chemical Treatments on the Surface Properties of Polyvinylchloride
Authors: Jeanneret C. , Stoeckli H. F.
Published: December 2004

The influence of thermal and chemical treatments (tetrahydrofuran and dioxane) on the adsorption properties of polyvinylchloride is investigated by gas chromatographic methods. It is shown, that heating to the glass‐transition temperature has an erasing effect. Methanol was used as the main molecular probe.
Diterpenoid Hydroquinones from Coleus Somaliensis (S. Moore): Coleons H, I, and K
Authors: Moir Michael , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Aus den Blättern und Stengeln von Coleus somaliensis (S. Morre) wurden die Diterpen‐Hydrochinone H, I und K (Coleone H, I und K) isoliert und ihre Struktur aufgeklärt. Coleon H ist 3α‐Acetoxy‐6,11, 12, 14, 16 (oder 17)‐pentahydroxy‐abieta‐5,8,11,13‐tetraen‐7‐on (2). Coleon I ist vermutlich das entsprechende A/B‐trans‐6,7‐Diketon 5. Coleon K ist 16,17‐Diacetoxy‐3α, 11, 12, 14‐tetrahydroxy‐abieta‐8,11,13‐trien‐6,7‐dion (6). Es sind die höchst hydroxylierten Coleone, die bisher aufgefunden worden sind.
Diterpenoids from coleus somaliensis (S. Moore): Coleons G, and J
Authors: Moir Michael , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Aus den Blättern und Stengeln von Coleus somaliensis (S. Moore) wurden die farblosen, tetracyclischen Diterpene Coleon G (C22H28O6) und Coleon J (C20H26O5) isoliert und vor allem aus Spektren (einschliesslich 270‐MHz‐1H‐ und 13C‐NMR.) für sie die Strukturen 2 und 1 abgeleitet. Wir fassen sie als Abietanderivate auf mit einer aus der oxydierten Isopropylgruppe entstandenen spiro‐Methylcyclopropan‐cyclohexendion‐Struktur. Sie enthalten zudem anstelle der geminalen Methylgruppen an C(4) eine α‐ständige Methyl‐ an C(3) und eine exocyclische Methylengruppe an C(4).
Dérivés C‐glycosyliques. XV Vinylogues d'homo‐C‐glycosides. Communication préliminaire
Authors: Tronchet Jean M. J. , Campanini Marie‐Thérèse , Denoyelle Josiane , Zumwald Jean‐Bernard
Published: December 2004

1,2‐O‐Isopropylidene‐3‐O‐methyl‐α‐D‐xylo‐pentodialdo‐1,4‐furanose and its 3‐O‐benzyl analog have been reacted with pyridinyl‐3‐methylenetriphenylphosphorane and benzimidazolyl‐2‐methylenetriphenylphosphorane. The unsaturated sugars so obtained are vinylogs of homo‐C‐glycosides whose conformation is easily determined. They constitute useful model compounds for pharmacologic studies.
Gleichgewichte der Protonenaddition an 1, 1‐Bis‐(4′, 4″‐dimethylaminophenyl)‐äthylen in Methanol und in Dimethylsulfoxid
Authors: Bernasconi Claude F. , Iijima Toshiro , Koch Werner , Wakae Masao , Zollinger Heinrich
Published: December 2004

The first and second proton addition equilibrium constants of 1,1‐bis‐(4′, 4″‐dimethylaminophenyl)‐ethylene (1) have been measured by the spectrophotometric method in methanol and in dimethylsulfoxide. Defined as acid dissociation constants of the mono‐ and diprotonated adduct they are: K1 (CH3OH) = 8.3 (± 0.9) · 10−6M, K2 (CH3OH) = 1.22 (± 0.06) · 10−4M, K1 (DMSO) = 2.3 (± 0.9) · 10−3M, K2 (DMSO) ≥ 1M. The evaluation of the electronic and the NMR. spectra demonstrates that the equilibrium of the two monoprotonated tautomers 2 (methyl‐carbenium ion) and 3 (ammonium ion) is, in methanol to about 96% on the side of the ammonium ion (tautomeric equilibrium constant K23 = [3]/[2] ≅ 23). The tautomer 2 cannot be detected in dimethylsulfoxide. The possible causes of these solvent effects are discussed.
Drei neue Mutterkornalkaloide aus saprophytischen Kulturen von Claviceps paspali Stevens et Hall. 77. Mitteilung über Mutterkornalkaloide [1]
Authors: Tscherter Hans , Hauth Hartmut
Published: December 2004

From saprophytic cultures of a strain of Claviceps paspali Stevens et Hall, which produces as main metabolite 6‐methyl‐Δ8,9‐ergolen‐8‐carboxylic acid, three new alkaloids of the clavine type were isolated. One is a dihydro derivative of setoclavine, the two others, which are named paspaclavine and paliclavine, represent new structural types.
1, 4‐Dimethylcyclohex‐3‐enyl Methyl Ketone
Authors: Kreiser Wolfgang , Haumesser Winfried , Thomas Alan F.
Published: December 2004

An improved one‐step synthesis of the title compound is described, the optical activity of the natural product is confirmed, and the NMR. spectral behaviour is explained.
Pyrolyse du Diméthylidène‐2, 3‐oxa‐7‐bicyclo[2.2.1]heptane
Authors: Vogel Pierre , Hardy Michèle
Published: December 2004

Benzocyclobutene 10 and 3‐oxabicyclo [3.2.0]hepta‐1, 4‐diene 11 are formed by gas‐phase pyrolysis of the title compound 9. The results are discussed with reference to the estimated reaction parameters. It is found that the activation due to oxygen in 9 is relatively weak in comparison to its effect on the reactivity of oxaquadricyclanes 1.
The stereochemistry of fragmentation products formed in the lead tetraacetate and related oxidations of alcohols. Part. I. β‐fragmentation of cis‐and trans‐4‐t‐Butylcyclohexanemethanol
Authors: Mihailovič Mihailo Lj. , Bošnjak Jovan , Čeković Živorad
Published: December 2004

The stereochemistry of β‐fragmentation products formed in the oxidation of cis‐and trans‐4‐t‐butylcyclohexaanemethanol with lead tetraacetate and with lead tetraacetate‐metal chloride combinations, under various reaction conditions, has been investigated, and the results compared with those obtained, under similar conditions, in the oxidative decarboxylation of cis‐and trans‐4‐t‐butylcyclohexanecarboxylic acid with the same reagents. It was found that all four substrates afford, under comparable conditions, identical cis‐trans proportions of the respective fragmentation products, and that, therefore, so far as steric course is concerned, both the initial homolytic and subsequent heterolytic processes involved in the lead tetraacetate fragmentation reaction are independent of the nature and configuration of the starting material.
Use of Dimethylsilyl Ethers for Characterizing Primary Aliphatic Alcohols: A comparison of mass spectrometric fragmentation of di‐ and trimethylsilyl derivatives
Authors: Richter Wilhelm J. , Hunnemann Don H.
Published: December 2004

Mass spectral fragmentation patterns of dimethylsilyl (DMS) ethers of primary unbranched, branched, and secondary unbranched aliphatic alcohols in the C5 to C10 range are compared with those of the corresponding trimethylsilyl (TMS) derivatives. Unlike their TMS analogues, DMS ethers of primary alcohols exhibit pronounced rupture of the CC bond adjacent to the oxygen atom within the alkyl moiety (loss of an alkyl radical R) in marked preference to cleavage within the silyl substituent (loss of CH3). Within this class of compounds, complementary preparation of DMS derivatives can therefore be used to establish or to confirm the site, and thus the primary nature of the hydroxyl group, whereas preparation of TMS ethers may be of advantage in deducing molecular size. For the derivatives of secondary alcohols this diagnostically useful difference in fragmentation behaviour is not observed.
Transpositions de doubles liaisons de terpènes bicycliques catalysées par des bases
Authors: Ferro Alberto , Naves Yves‐René
Published: December 2004

The displacements of double bonds and dehydrogenation by basic catalysts are examined by analogy with the preceding studies on p‐menthenes and p‐menthadienes [1] with bicyclic terpenes: α‐ and β‐pinenes, sabinene and 3‐carene.
Azidiniumsalze. 11.Mitteilung [1]. Struktur‐Reaktivitäts‐Beziehungen in Serien quartärer N‐Heteroaromaten: Polarographische Untersuchungen an heterocyclischen Azidiniumsalzen
Authors: Hellrung Bruno , Balli Heinz
Published: December 2004

Die polarographischen Halbstufenpotentiale von neun Azidiniumsalzen mit verschiedenem Heterocyclus wurden in wässeriger, gepufferter Lösung und in Sulfolan bestimmt. Die Messergebnisse in den beiden Lösungsmitteln werden miteinander und mit σHet‐Konstanten [1] [3] verglichen. – Die Korrelation der Halbstufenpotentiale mit den σHet‐Konstanten ist unbefriedigend. Messergebnisse und Korrelationen werden diskutiert.
Adducts of Niobium(V) and Tantalum(V) Halogenides. IX. Relative stability of the adducts of the chlorides and bromides with some dialkylchalcogenides
Authors: Good René , Merbach André E.
Published: December 2004

The relative stability of adducts formed by Nb(V) and Ta(V) pentachlorides and bromides with some dimethylchalcogenides and nitriles has been determined by 1H‐NMR. in dichloromethane at − 60°. The stabilities are explained in terms of the HSAB principle and Jørgensen's symbiotic effect. A good correlation exists between the ionisation potential of the valence p orbital of the chalcogen atom in the ligand and the logarithm of the relative stability of the adduct formed with a given acid.
Synthese von 1,6‐Trimethylen‐3‐methoxycarbonyl‐4‐methyl‐2‐pyridon
Authors: Fuhrer Walter , Hobi Reinhard , Pfaltz Andreas , Schneider Peter
Published: December 2004

The reaction sequences shown in schemes 3 and 4, represent a new method for the synthesis of a substituted pyridone‐system, starting from a vinylogous amide or thioamide and malonic ester.
Utilisation d'ylides du phosphore en chimie des sucres. XX. Synthèse de sucres acétyléniques et réarrangment d'intermédiaires carbénoïdes. Communication préliminaire
Authors: Tronchet Jean M. J. , Gonzalez Alberto , Zumwald Jean‐Bernard , Perret Françoise
Published: December 2004

Two novel methods for the synthesis of terminal acetylenic sugars, both involving a chain extension by one carbon unit, are described. In the first procedure, an aldehydo‐sugar is treated with dibromomethylenetriphenyl‐phosphorane, then with n‐butyllithium and finally with water. The second method involves an one‐step reaction between an aldehydo‐sugar and dimethyl diazomethylphosphonate. The acetylenic sugars obtained are valuable synthetic intermediates for the preparation of heterocyclic C‐nucleosides by 1,3‐dipolar cycloaddition reactions and some examples of syntheses of this type are described. Treatment of keto‐sugars with dimethyl diazomethylphosphonate led to an intermediate carbenoid species which reacted by insertion into a CH bond in one case and underwent nucleophilic attack by a methoxy group in a second case.
Der massenspektrometrische Zerfall von Tetralin‐Derivaten Beitrag zur massenspektrometrischen Retro‐Diels‐Alder Reaktion
Authors: Heimgartner Heinz , Weibel Peter A. , Hesse Manfred
Published: December 2004

The mass spectral decomposition of the 1‐tetralol derivatives 2, 3 and 4 in view of the retro Diels‐Alder reaction is investigated, for which deuterated derivatives, high resolution data and metastable peaks were used. By these studies it follows that the decyclisation reaction on ring A possesses the character of a retro Diels‐Alder reaction only in some part. The main mass spectral degradation is forced by the substituents placed thereon.
Selektive Synthesen mit Organometallen I. Konfigurativ einheitliche Folgeprodukte aus Alkenylkalium‐Zwischenstufen
Authors: Schlosser Manfred , Hartmann Jürgen , David Victor
Published: December 2004

Methyl groups in positions adjacent to an olefinic double bond can be metalated without cis/trans isomerisation. On the other hand configurational changes can be brought about via metalotropy; under equilibrium conditions the Z isomers (metal cis to an alkyl in β position) predominate overwhelmingly. This behaviour opens new stereoselective routes of high preparative utility.
Reaktionen von Glutaminsäuredimethylester im Massenspektrometer. 21. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen
Authors: Lerch Elsbeth , Hesse Manfred
Published: December 2004

The mass spectral fragmentation of dimethyl glutamate (1) and its deuterated derivatives 1a, 1b and 1c has been investigated. By loss of a methoxycarbonyl group from the molecular ion an ion of m/e 116 is generated. The latter splits off methanol (m*), the resulting fragment of m/e 84 giving raise to the base peak of the spectrum. Only part of the hydrogen transferred to the leaving group originates from thc amino group, as was suggested earlier [2] [3]. Basing on experiments with deuterated compounds we propose an additional mechanism for the reaction, i.e. hydrogen transfer from C(3) to methoxyl. The fragment generated by both processes is most likely to be a pyrrolinonium ion. Thermal side reactions in the mass spectrometer (formation of pyroglutamic acid ester) followed by fragmentation may lead to the same ion. – The mechanisms discussed are supported by the mass spectral fragmentation of N‐acetyl‐glutamic acid diesters 3, 3a, 3b and 3d and of the N, N‐dimethyl derivatives 4 and 4a. – The fragmentation reactions investigated are similar to some of 1,3‐trimethylenediamine derivatives [7]. This means that there are parallels in the mass spectral fragmentation of difunctional compounds irrespective of the nature of the functional groups.
Cycloadditionen von Heterocumulenen an CN‐Bindungssysteme. 3. Mitteilung. Bildung von Dihydro‐1,3,5‐oxadiazin‐ und Perhydro‐s‐triazinthionen bei der Reaktion von Iminodithiocarbonaten und Azomethinen mit Aroylisothiocyanaten
Authors: Milzner Karlheinz , Seckinger Karl
Published: December 2004

The iminodithiocarbonates 5a–5g and the N‐(p‐methoxybenzylidene)amines 6a–61 undergo 4 + 2‐cycloaddition with the aroyl isothiocyanates 4a–4f to yield the expected dihydro‐1,3,5‐oxadiazine‐4‐thiones 7, 8 and 14.

The addition of the aroyl isothiocyanates 4a–4f to the azomethines 11a–11c and 15a–15f, however, furnishes both the 4 + 2‐cycloaddition products 12 and 16 and the perhydro‐s‐triazine‐2‐thiones 13a–13j. The mechanism of formation is discussed.
Grignard‐Addition an Pyridin‐N‐oxid
Authors: Schiess Peter , Monnier Charles , Ringele Peter , Sendi Ebrahim
Published: December 2004

Addition of phenyl‐, alkyl‐, alkenyl‐ and alkinyl‐Grignard reagents to pyridine‐N‐oxide in THF leads to 5‐substituted (2Z, 4E)‐pentadien‐aldoximes 6 having (E) (syn)‐configuration of the C, N‐double bond. The unsaturated oximes are shown to arise through an electrocyclic ring opening reaction from the primary Grignard adducts 5. These can be trapped by protonation at low temperature.
Isolierung, Konstitution und Synthese der (R)‐(−)‐Eucominsäure
Authors: Heller Werner , Tamm Christoph
Published: December 2004

From the bulbs of Eucomis punctata L'Hérit. (Liliaceae) and of a hitherto undefined species of Eucomis a new optically active phenolic carboxylic acid, eucomic acid, was isolated. Structure 1 was assigned on the basis of chemical and spectral evidence. The absolute configuration of eucomic acid was determined by its correlation with piscidic acid ((2 R, 3 S)‐2‐(4′‐hydroxybenzyl)‐tartaric acid) (8). Consequently, eucomic acid is (R)‐(−)‐2‐(4′‐hydroxybenzyl)‐malic acid (1). For the stereospecific synthesis, methyl cis‐p‐methoxybenzylidene‐succinic acid (22) was transformed into the γ‐lactone 24 which, by catalytic hydrogenolysis, yielded (±)‐2‐(4′‐hydroxybenzyl)‐malic acid 1‐methyl ester (27). Resolution with (−)‐quinine led to the enantiomeric acids 29 and 30. The methyl ester of the levorotatory enantiomer 30 was identical with the dimethyl ester 3 of 4′‐O‐methyl‐eucomic acid.
Biosynthese der Cytochalasane. Teil II Die Grundbausteine von Cytochalasin D
Authors: Lebet Claude‐René , Tamm Christoph
Published: December 2004

A number of potential 14C‐ and 3H‐labelled precursors were fed to growing cultures of Zygosporium masonii after the rate of formation of cytochalasin D had been measured. By chemical degradation of [14C]‐ and [3H, 14C]‐cytochalasin D the distribution of the radioactivity originating from incorporated [4′‐3H, U‐14C]‐L‐phenylalanine and [CH3‐14C]‐L‐methionine was determinated. The results demonstrate that the building blocks of cytochalasin D are 1 unit of pheylalanine, 3 units of methionine and acetate units.
Silberioneninduzierte Reaktion von 3‐Chlor‐2‐pyrrolidinocyclohexen mit 1,3‐Dienen. Vorläufige Mitteilung
Authors: Schmid Rudolf , Schmid Hans
Published: December 2004

3‐Chloro‐2‐pyrrolidinocyclohexene (3) in the presence of silver tetrafluoroborate in methylene chloride at −60° underwent cycloadditions with various 1,3‐dienes; the resulting iminium tetrafluoroborate salts 4a–8a were hydrolysed to give the bicyclic and tricyclic ketones 4b–8b. The addition reactions can be regarded as [3+4]‐cycloadditions of an intermediate 2‐aminoallyl cation.
13C‐NMR. Spectroscopy of Naturally Occurring Substances. XXXII. Vincaleucoblastine and related alkaloids
Authors: Wenkert Ernest , Hagaman Edward W. , Lal Bansi , Gutowski Gerald E. , Katner Allen S. , Miller Jean C. , Neuss Norbert
Published: December 2004

The total assignment of the 13C‐shifts of the complex Vinica rosea L. alkaloids vincaleucoblastine, leurosidine and leurosine and of a synthetic isomer of the latter is presented. The structure of leurosidine is corrected and a tentative structure for the acid‐catalyzed product of isomerization of leurosine is proposed.