bluuebunny/crossref_metadata_2025_split huggingface dataset:
Die Chemie des Wieland‐Gumlich‐Aldehyds und seiner Derivate [1] 136. Mitteilung über Alkaloide [2]
Authors: Hymon J. R. , Schmid H. , Karrer P. , Boller A. , Els H. , Fahrni P. , Fürst A. 
Published: December 2004

AbstractThe course of the reactions involved in the process of degradation of strychnine (1) to Wieland‐Gumlich aldehyde (WGA) (2), first performed by Wieland, Kaziro & Gumlich, has been elucidated. 23‐Isonitrosostrychnine hydrochloride (9a) upon treatment with thionyl chloride undergoes a fragmentation (2nd order Beckmann rearrangement), thus furnishing N(a)‐cyanoformyl‐WGA hydrochloride (14a). On heating in an acidic medium, the latter compound is transformed — at least partially via the cyclic urethane 15 — into WGA (2), which is an important keyintermediate in the syntheses of strychnine and curare alkaloids. The compound 2 can now be obtained in high purity and good yield.A corresponding degradation has been realized with quaternary analogues (27 → 3) as well as with 10‐chlorostrychnine (58 → 62).10‐Chlorostrychnine (58) was prepared by chlorination of strychnine with chlorine in conc. hydrochloric acid according to Leuchs & Steinborn. As by‐products of the reaction, 10, 15‐dichlorostrychnine (59) and 10, 15, 19‐trichlorostrychnine (60) could be identified.Starting from WGA a series of derivatives have been prepared. Special mention is made of the two epimeric methyl ethers 18 and 19. The absolute configuration at the centre 17 of WGA and of these two substances has been established by optical comparisons of 3 epimeric pairs.The methyl ether 18, by‐product «B», is obtained if methanol is used in working up the Beckmann rearrangement products of 23‐isonitrosostrychnine hydrochloride (9a).A second by‐product, «A», results by working up under alkaline conditions. This compound has the structure 44 with inverted configuration at centre 16. Degradation of 44 under controlled conditions leads either to WG‐diol (42) or to 16‐epi‐WG‐diol (51).Besides «Az.rdang; and «B» a series of by‐products and intermediates (16, 17, 11a, 22. 23, 24 and 25) could be detected in the course of the process of strychnine degradation.
BIRCH‐Reduktion von [2.2] Metacyclophan
Authors: Reiner J. , Jenny W. 
Published: December 2004

AbstractMetal‐ammonia‐reduction of [2.2] metacyclophan led to 5, 8, 13, 16‐tetrahydro‐[2.2] metacyclophan (II). The structure of this new ring system was confirmed by UV.‐, NMR.‐and mass spectra analyses. The NMR.‐spectrum of II in solution shows an AA′ BB′‐system for the ‐CH2CH2‐groups. This part of the spectrum is temperature dependant. It collapses and coalesces to a broad singlet at approximately 145°C. A chair‐like conformation and conformational changes of II are discussed.
Mikrobiologische Umwandlung von bicyclischen Monoterpenen durch Absidia orchidis (VUILL.) HAGEM. 1. Teil: Reduktion von Campherchinon und Isofenchonchinon. 17. Mitteilung über Reaktionen mit Mikroorganismen [1]
Authors: Pfrunder B. , Tamm Ch. 
Published: December 2004

Abstract(—)‐Camphorquinone (1a) was transformed to a mixture consisting of 3‐endo‐hydroxy‐camphor (2a) (40%), 3‐exo‐hydroxy‐camphor (3a) (30%) and 2‐endo‐hydroxy‐epicamphor (4a) (30%) by an aqueous suspension of the mycelium of Absidia orchidis (Vuill.) Hagem. The composition of the reduction products was determined by the NMR. spectra. Incubation of the enantiomeric (+)‐camphorquinone (1b) under the same condition yielded 3‐exohydroxy‐camphor (3b) as single product. Since both substrates form their products immediately and in the same ratio the possibility of a posterior isomerization of 3a yielding the ketols 2a and 4a can be ruled out. For comparison the course of the chemical reduction of camphorquinone (1) to the ketols (Zn in acetic acid, hydrogenation with Raney‐Ni as catalyst, NaBH4) was investigated. Camphor was not transformed by Absidia orchidis. (—)‐Isofenchonequinone (6a) yielded upon incubation with an aqueous suspension of the mycelium of Absidia orchidis exclusively 2‐endo‐hydroxy‐epi‐isofenchone (7a). The enantiomer diketone 6b gave the same result, i. e. the ketol 7b as the only transformation product. Also with isofenchonequinone the chemical reduction to the ketols by Zn in acetic acid, hydrogenation with Raney‐Ni as catalyst and NaBH4 was studied.
Das biologische Verhalten von Fettsäuren mit Dreifachbindung. IV. Der Abbau der Crepissäure (9‐Octadecen‐12‐insäure) im Tierkörper
Authors: Bernhard Karl , Kaempf Ekkehard 
Published: December 2004

AbstractCrepenynic acid (9‐octadecen‐12‐ynoic acid) fed to rats as naturally occurring triglyceride is not incorporated into brain and liver lipids, and into the depot fat only to a small amount. As a metabolite the previously unknown 4‐decynedioic acid was isolated from the urine.
Das 13C‐INDOR‐Spektrum des A3X‐Systems einer Methylgruppe
Authors: Wehrli F. W. , Simon W. 
Published: December 2004

AbstractThe natural abundance 13C INDOR spectrum of the A3X system of the methyl group in a substituted toluene was investigated at a very small value of the perturbing rf field H2. The relative line intensities can be explained in terms of a redistribution of the equilibrium spin populations due to the polarizing field H2. The double resonance method is suggested for accurate determination of the chemical shift of 13C in medium‐size compounds where the carbon atom under consideration couples with only one set of magnetically equivalent hydrogen nuclei.
Synthèse d'isocarbostyriles et de chloro‐1‐isoquinoléines
Authors: Eloy F. , Deryckere A. 
Published: December 2004

AbstractA partir d'acides cinnamiques substitués on a préparé les styrylisocyanates correspondants qui, par cyclisation thermique, ont fourni des isocarbostyriles que l'action de l'oxychlorure de phosphore transforme en chloro‐1‐isoquinoléines. Ce procédé de synthèse s'est montré supérieur aux méthodes connues.
Mechanismus der Bildung und des Zerfalls von Amidkomplexen, I Kupfer (II) und N, N′‐Diglycylpropylendiamin
Authors: Wagnerová D. , Kaden Th. , Zuberbühler A. 
Published: December 2004

AbstractThe kinetics of the formation and dissociation of the copper (II) complex with N, N′‐Diglycyl‐propylendiamine has been studied. In the formation reaction an intermediate was observed, the structure and reactivity of which is discussed. The rate of dissociation of the complex is proportional to [H+]2. This is explained by a rapid proton addition to one of the amino groups, followed by the slow reaction of a second proton with the coordinated amide group. The effect of acetate buffer, which increases the dissociation rate, is discussed.
Über Derivate von 9, 10‐Methaniminomethano‐ 9, 10‐dihydroanthracen
Authors: Blaser R. , Imfeld P. , Schindler O. 
Published: December 2004

AbstractIm Unterschied zur BECKMANN‐Umlagerung des Oximes I, welche zum Nitril II führt, resultiert aus dem SCHMIDT‐Abbau des Ketones IV das tetracyclische Amid V. Dessen Konstitution ist gesichert durch die Überführung in XII. LiAIH4‐AlCl3‐Reduktion von V liefert das tetracyclische Amin IX.
Massen‐ und Ladungsverteilung bei der Spaltung von 249Cf mit thermischen Neutronen. Vorläufige Mitteilung
Authors: Flynn K. F. , von Gunten H. R. 
Published: December 2004

AbstractThe distribution of mass and charge in the thermal‐neutron‐induced fission of 249Cf has been investigated by radiochemical determination of the fission yields of 25 mass chains and one shielded nuclide (independent yield). The mass distribution is asymmetric, as in all known cases of low‐energy fission. The fission yield data indicate a value of 6 ± 1.5 for v, the average number of neutrons emitted per fission. The division of nuclear charge, as indicated by the independent yield of 136Cs, is consistent with the equal charge displacement hypothesis characteristic of low‐energy fission.
Derivate des 5, 6‐Dihydro‐p‐dithiin‐2, 3‐dicarbonsäureanhydrids, II: N‐Amino‐imide und cyclische Hydrazide
Authors: Schweizer H. R. 
Published: December 2004

Abstract5. 6‐Dihydro‐p‐dithiin‐2. 3‐dicarboxylic anhydride reacts with hydrazine to form the N‐amino‐imide; the six‐membered cyclic hydrazide is formed only in minor amounts. 1‐Substituted and 1. 1‐disubstituted hydrazines form exclusively N‐amino‐imides. All N‐amino‐5.6‐dihydro‐p‐dithiin‐2. 3‐dicarboximides have fairly strong, bright greenish‐yellow colours, but are of no practical value as dyes or pigments.
Zusammensetzung und strukturelle Eigenschaften des „zweiwertigen”︁ Kobaltcyanids
Authors: Güdel H. U. , Ludi A. 
Published: December 2004

AbstractThe products obtained by mixing aqueous solutions of cobalt (II) chloride and potassium or hydrogen cyanide are nonstoichiometric compounds Co(CN)x, yH2O whith x between 2.2 and 2.4 and y between 1.75 and 2.15. They have a cubic face‐centered unit cell with a = 10.20 ± 0.02 Å and Z between 6.8 and 7.1 (Z = number of units Co (CN)x yH2O per cell). Infrared spectra show that there is zeolitic as well as coordinated water present. The coordination units derived from reflectance spectra in the ultraviolet and visible region are (CoIII)C6 and CoIIN6‐xOx. There exists a close structural relationship between Co(CN)x, yH2O and the stoichiometric compound Co3[Co(CN)6]2, zH2O. Comparison of calculated with experimental density shows that there must be holes in the threedimensional CoCNCo‐framework, which can be occupied by water molecules.
Über die Oxydation von Manganoxidhydroxid
Authors: Giovanoli R. , Leuenberger U. 
Published: December 2004

AbstractThe oxidation of γ‐MnOOH (manganite) in oxygen and its disproportionation in HNO3 lead topotactically to β‐MnO2. The oxidation of synthetic α‐MnOOH (groutite) in oxygen depends on its cristallite size; finely divided crystals oxidise rapidly to Mn5O8 which usually is stable but yields β‐MnO2 by further oxidation. Larger crystals of disperse synthetic α‐MnOOH are topotactically transformed to γ‐MnO2. In HNO3 α‐MnOOH disproportionates into γ‐MnO2 and Mn2+. Though strictly topotactical, the reaction α‐MnOOH → γ‐MnO2 is not single‐phase as might be expected. The discontinuity in the function: JAHN‐TELLER distortion vs. reaction rate, may simply be interpreted as the crosspoint of two different functions attributed to the crystal species α‐MnOOH and γ‐MnO2, respectively. This distortion confirms the presence of Mn3+ in manganite and nsutite. The wide variety of possible X ray powder patterns of the phase γ‐MnO2 is explained by the superposition of, (i) cristallite size broadening, (ii) intergrowth structure effects on the profile, and (iii) BRAGG angle shifts due to substitution of part of Mn4+ by Mn3+.
Extension de la méthode du «logarithme limite» [1] pour la détermination de la composition et de la constante de stabilité des complexes
Authors: Marcantonatos M. , Monnier D. 
Published: December 2004

AbstractA study of the conditions of applicability to weak complexes of the relation log x = v log V + log (βv,cCc) = f(logV), where V and C are variable and constant total concentrations of the constituants of the complexe, shows that for conditions other than C ≫ V, another function φ(log V) accounts better for the formation equilibrium of the complexe.From f(log V) and φ (log V) a relation t(log V) is derived whose simple analysis permits the determination of the composition and the stability constant of weak complexes.Applications are given to 1:1, 1:2, 2:2 composition.
Darstellung und spektroskopische Untersuchungen von Kupferkomplexen mit verschiedenen Mikrostrukturen. II Stereochemie und Elektronentransferspektren von Halogeno‐Stickstoffbasen‐Kupfer (II)‐Komplexen
Authors: Ludwig W. , Gasser F. 
Published: December 2004

AbstractEs werden die Elektronenspektren oberhalb der Ligandenfeldübergänge von CuL2X2‐Komplexen unidentater Stickstoffbasen mitgeteilt. Es wird der Zusammenhang zwischen Stereometrie und den Elektronentransferübergängen beschrieben und diskutiert, sowie ein Vorschlag für die Indizierung der Absorptions‐ und Reflexionsspektren gemacht. Die Untersuchungsergebnisse machen wahrscheinlich, dass neben den ligandinternen π → π*‐Übergängen bei den Pyridinbasen‐Komplexen Elektronentransferübergänge vom Typ X → M, aber keine «inversen» Elektronentransferübergänge M → π* (L) auftreten.
L'hydrolyse acide des diazocétones alcoylées: Formation d'ions α‐acylcarbonium secondaires
Authors: Dahn H. , Ballenegger M. 
Published: December 2004

AbstractHydrolysis of secondary diazoketones CH3COCN2R (R  Me, Et, isopropyl) by aqueous perchloric acid is characterized by rate‐determining protonation demonstrated by solvent isotope effects kD2O/kH2O = 0,4–0,6 and by the intervention of general acid catalysis. The product determining step, yielding keto‐alcohols and keto‐olefines, is independent of added nucleophiles; this is interpreted as resulting from the intermediate formation of (more or less free) αhyphen;ketocarbonium is ions. The hydride shift observed wih III (R = isopropyl) supports this interpretation. The difference between hydrolysis of primary and of secondary diazoketones is discussed.
Calicen Hochpolare Dicyan‐diphenyl‐derivate [1] [2]. Vorläufige Mitteilung
Authors: Prinzbach H. , Woischnik E. 
Published: December 2004

AbstractThree dicyano‐diphenyl‐calicenes have been synthesized. Judged by the dipole moments, the uv. and nmr. data, there is appreciable charge separation in the ground states.
La migration de groupes carboxamides lors de la transposition benzilique d'amides α,β‐dicarbonylés. 24e Communication sur les réductones et les composés tricarbonylés‐1,2,3 [1]
Authors: Dahn H. , Karoui S. 
Published: December 2004

AbstractUnder the conditions of the benzilic acid rearrangement, α,β‐diketobutyryl‐di‐phenylamide (Ia) and ‐N‐methylanilide (Ib) are transformed into tartronic acid derivatives (VI), which decarboxylate to lactamides VII. It is proved by 14‐labelling of Ia, that the reaction takes place by carbonamide group migration.The reaction was followed kinetically by polarography at a fixed potential; at low pH the velocity is proportional to [OH⊖], at higher pH it becomes independent of [OH⊖], which is explained by complete transformation of I into its hydrate‐anion. The equilibrium between I and its hydrate was measured by UV.‐spectroscopy.
Cinétique du coupage de la fluorescence du p‐terphényle en solution
Authors: Cosandey‐Tenthorey Maurice , Haralambof Vladimir 
Published: December 2004

AbstractThe quenching effect in a solution of p,‐terphenyl in toluene has been studied for an aliphatic and an aromatic ketone. The rate constant of the quenching effect has been determined by three methods, and found to be independent of the choice of the particular method. FÖRSTER'S resonance theory can be applied successfully.
ESR.‐Messungen an Radikal‐Anionen Trimethylsilyl‐substituierter Hetero‐π‐Systeme
Authors: Gerson F. , Krynitz U. , Bock H. 
Published: December 2004

AbstractThe ESR. spectra of the radical anions of trimethylsilyl‐substituted derivatives of p‐benzoquinone, phenylketone, diimine, p‐benzoquinone‐diimide, aniline and p‐phenylenediamine are reported. In most cases the coupling constants of 29Si isotopes in natural abundance have been measured. The comparison of the ESR. data for the radical anions of the trimethylsilyl derivatives with those for the radical anions of the corresponding parent hydrocarbons and/or alkyl‐substituted compounds provide additional evidence for the overall electron withdrawing effect of the trimethylsilyl substituent (Si←Cπ and Si←nπ delocalization).
Synthèse de C‐glycosides dérivés du pyrazole et de l'isoxazole. Communication préliminaire
Authors: Trochet J. M. J. , Jotterand A. , Le‐Hong N. 
Published: December 2004

AbstractBromination of 2.3:4.5‐di‐O‐isopropylidene‐aldehydo‐D‐arabinose p‐nitrophenyl‐hydrazone affords the corresponding hydrazidic bromide. Similarly, chlorination of 3‐O‐benzyl‐1,2‐O‐isopropylidene α‐D‐xylo‐pentodialdo‐1,4‐furanose oxime leads to the corresponding hydroxamoyl chloride. These two compounds constitute useful new synthetic intermediates in carbohydrate chemistry. For example, they may be ethynylated, then cyclised respectively to pyrazolyl‐ and isoxazolyl‐C‐glycosides.
Cyclization of the Enol Esters of o‐Acyloxyphenyl Alkyl Ketones, IV. A kinetic study of the steps of the KOSTANECKI‐ROBINSON reaction
Authors: Széll T. , Kovács K. , Zarándy M. S. , Erdőhelyi Á. 
Published: December 2004

AbstractIn a study of the KOSTANECKI‐ROBINSON reaction of 2,4‐diacetoxy‐6‐hydroxy‐propiophenone the rate constants and the order of each step have been approximately determined and compared. Mechanism for the reaction is suggested.
Höhere, kondensierte Ringsysteme. 5. Mitteilung[1]. Makrocyclen mit überbrückten 9, 10‐Dihydrophenanthreneinheiten
Authors: Paioni R. , Jenny W. 
Published: December 2004

AbstractStarting from 2, 7‐diacetyl‐9, 10‐dihydrophenanthrene, 2, 7‐dichloromethyl‐9, 10‐dihydrophenanthrene was synthesized through a serie of a new compounds. By a modified Wurtz reaction the dichloromethyl compound led to hexahydro‐[23] (2,7) phenanthrenophane and decahydro‐[25] (2,7) phenanthrenophane. [23] (2,7) phenanthrenophane was obtained by dehydrogena tion of hexahydro‐[23] (2,7) phenanthrenophane with Pd/C. The structure of these new ring systems was confirmed by UV.‐, NMR.‐ and mass spectroscopy.
Photofragmentierung von Cyclohexa‐1,3‐dien‐5,6‐dicarbonsäure‐anhydriden [1]
Authors: Kitzing R. , Prinzbach H. 
Published: December 2004

AbstractThe photochemical elimination of the anhydride function («C2O3») from the dihydrobenzenoid anhydrides 6a‐6c is described. Some applications and limitations of this double bond producing reaction are given. A formal correlation between ease of «C2O3» elimination upon irradiation and upon electron impact respectively is indicated.
Zur Stabilität und Struktur der CuI‐Komplexe des Imidazols und Histamins. Chemie des einwertigen Kupfers in homogener, polarer Lösung. 1. Mitteilung
Authors: Sigwart C. , Kroneck P. , Hemmerich P. 
Published: December 2004

AbstractUnivalent copper is stabilized in aqueous medium by the non‐protophilic ligand CH3CN, allowing ligand displacement reactions to be investigated as if a stable CuI‐hydrate did exist. Under these conditions the formation of CuI‐complexes with imidazole and its derivatives has been studied in polar solution in the absence of CuII. Imidazole (ImH) acts upon CuI as a bidentate ligand forming polynuclear chains according to the equation
equation image
Histamine reacts in the same way, i. e. the coordination number of CuI does not exceed 2; by comparison of the complexes of CuI with histamine and its N‐methyl‐derivatives it is shown that no six‐membered chelate – which sterically would be possible – is built up. Trigonal as well as tetrahedral coordination of CuI – i. e. chelate formation – in dilute polar solutions are confined to π‐ or d‐acceptor ligands, e. g. bipyridine or methionine. Conclusions are drawn from this on the requirements for redox‐active copper in proteins.
Über Oxidhydroxide des vierwertigen Mangans mit Schichtengitter. 1. Mitteilung. Natriummangan (II, III)manganat(IV)
Authors: Giovanoli R. , Stähli E. , Feitknecht W. 
Published: December 2004

AbstractThe preparation of Na4Mn14O27, 9H2O (hitherto named manganomanganite or δ‐MnO2) by oxidation of a fresh Mn(OH)2 suspension in aqueous NaOH by molecular oxygen, and its probable structure are described. It is a double layer manganate (IV) structure resembling other manganates such as chalcophanite. Orthorhombic unit cell parameters are, a0 = 8,54, b0 = 15,39, c0 = 14,26 Å. In diluted nitric acid topotactical transition to manganese (III) manganate (IV), Mn7O13.5H2O (unit cell: a0 = 2,84, c0 = 7,27 Å; primitively hexagonal), and by prolonged digestion to nsutite, γ‐MnO2, occurs.
Säurekatalysierte Isomerisierung von (−)‐a‐Copaen‐epoxid
Authors: Ohloff G. , Pawlak M. 
Published: December 2004

AbstractDie Epoxy‐Verbindung 2 des (−)‐α‐Copaens (1) geht bei der Behandlung mit schwachen Säuren unter molekularer Umlagerung in zwei Alkohole (3 und 5) der (−)‐α‐Muurolen‐Reihe über, während sich der dritte (4) vom (+)‐δ‐Cadinen ableitet. (−)‐3β‐Hydroxy‐T‐muurolol (5) ist ebenso wie der entsprechende Ketoalkohol 6 mit den beiden Naturprodukten identisch.
Zur Kinetik des Diffusionsvorgangs bei Adsorptionsuntersuchungen nach dem Zweielektrodenverfahren
Authors: Schmidt E. , Siegenthaler H. 
Published: December 2004

AbstractDie Kinetik des Transports der adsorbierbaren Spezies bei Adsorptions‐messungen nach dem Zweielektroden‐Dünnschichtverfahren wird anhand eines linearen Diffusionsmodells untersucht. Es wird die Lösung des zugehörigen Differentialansatzes angegeben und die Beziehung zwischen den an beiden Elektroden herrschenden Flüssen diskutiert. Ein Verfahren zur Errechnung des Flusses an der Messelektrode aus Momentanwerten des Flusses an der Generatorelektrode durch Reihenentwicklung wird angeführt. Es wird nachgewiesen, dass die Existenz eines zeitlichen Grenzwerts des Integrals über den Messelektrodenfluss die Existenz eines identischen Grenzwertes des Generatorflussintegrals impliziert.
Über Pterinchemie. 29. Mitteilung. Hydroxylierung der Phenylreste in Phenylalanylpeptiden mittels Tetrahydropterin unter physiologischen Bedingungen
Authors: Viscontini M. , Mattern G. 
Published: December 2004

AbstractDie Ausbeuten an Tyrosinen bei der Hydroxylierung von Peptiden, in denen das Phenylalanin eingebaut ist, sind gegenüber jenen bei der Hydroxylierung von freiem Phenylalanin bedeutend geringer. Besonders herabgesetzt wird die Bildung von o‐bzw, m‐Tyrosin. Wir nehmen an, dass dies auf die sterische Hinderung der Phenylgruppe im Komplex zurückzuführen ist, in dem Eisen als Zentralatom und Tetrahydropterin, Sauerstoff und Peptid als Liganden vorliegen.
Thermische Lactonisierung von Estern γ‐Brom‐α, β‐ungesättigter Carbonsäuren zu Δα‐Butenoliden. Direkte γ‐Bromierung von α, β‐ungesättigten Säuren
Authors: Löffler A. , Norris F. , Taub W. , Svanholt K. L. , Dreiding A. S. 
Published: December 2004

AbstractBy heating with iron powder at 120–150° some γ‐bromo‐α, β‐unsaturated carboxylic methyl esters, and, less smothly, the corresponding acids, were lactonized to Δ7alpha;‐butenolides with elimination of methyl bromide. The following conversions have thus been made: methyl γ‐bromocrotonate (1c) and the corresponding acid (1d) to Δα‐butenolide (8a), methyl γ‐bromotiglate (3c) and the corresponding acid (3d) to α‐methyl‐Δα‐butenolide (8b), a mixture of methyl trans‐ and cis‐γ‐bromosenecioate (7c and 7e) and a mixture of the corresponding acids (7d and 7f) to β‐methyl‐Δα‐butenolide (8c). The procedure did not work with methyl trans‐γ‐bromo‐Δα‐pentenoate (5c) nor with its acid (5d).Most of the γ‐bromo‐α, β‐unsaturated carboxylic esters (1c, 7c, 7e and 5c) are available by direct N‐bromosuccinimide bromination of the α, β‐unsaturated esters 1a, 7a and 5a; methyl γ‐bromotiglate (3c) is obtained from both methyl tiglate (3a) and methyl angelate (4a), but has to be separated from a structural isomer. The γ‐bromo‐α, β‐unsaturated esters are shown by NMR. to have the indicated configurations which are independent of the configuration of the α, β‐unsaturated esters used; the bromination always leads to the more stable configuration, usually the one with the bromine‐carrying carbon anti to the carboxylic ester group; an exception is methyl γ‐bromo‐senecioate, for which the two isomers (cis, 7e, and trans, 7d) have about the same stability.The N‐bromosuccinimide bromination of the α,β‐unsaturated carboxylic acids 1b, 3b, 4b, 5b and 7b is shown to give results entirely analogous to those with the corresponding esters. In this way γ‐bromocrotonic acid (1 d), γ‐bromotiglic acid (3 d), trans‐ and cis‐γ‐bromosenecioic acid (7d and 7f) as well as trans‐γ‐bromo‐Δα‐pentenoic acid (5d) have been prepared.Iron powder seems to catalyze the lactonization by facilitating both the elimination of methyl bromide (or, less smoothly, hydrogen bromide) and the rotation about the double bond.α‐Methyl‐Δα‐butenolide (8b) was converted to 1‐benzyl‐(9a), 1‐cyclohexyl‐(9b), and 1‐(4′‐picoly1)‐3‐methyl‐Δα‐pyrrolin‐2‐one (9 c) by heating at 180° with benzylamine, cyclohexylamine, and 4‐picolylamine.The butenolide 8b showed cytostatic and even cytocidal activity; in preliminary tests, no carcinogenicity was observed. Both 8b and 9c exhibited little toxicity.