bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthèse de la diméthyl‐4,4‐dihydrofuranedione‐2,3
Authors: Fizet Christian 
Published: December 2004

Abstract4,4‐Dimethyl‐dihydro‐2,3‐furanedione (4), an intermediate in the synthesis of (+)‐D‐pantothenic acid, is obtained in good yield from readily available substances such as isopropyl chloride, diethyl oxalate and formaldehyde, without oxidative conditions.
1,2‐Shift of a Carboxyl Group in a Wagner‐Meerwein Rearrangement
Authors: Berner Daniel , Cox D. Philip , Dahn Hans 
Published: December 2004

AbstractOn treatment with HSO3F in SO2C1F at 0°, 3‐hydroxy‐2,2‐dimethyl‐3‐phenyl‐propionic acid (1a) is transformed into 2‐phenyl‐3‐methyl‐2‐butenoic acid (2a) (isolated yield: 40–44%). Using monolabelled [3‐13C]‐1a (1a*) and doubly labelled [1,3‐13C2]‐1a (1a**), the migration of HOOC (or a mechanistically equivalent group) was proved; a cross experiment established the intramolecular character of the rearrangement. By following the reaction at low temperature in an NMR. spectrometer, the formation of intermediates and side products was demonstrated.
Concerning the Stereochemical Course and Mechanism of the Photochemical 1,3‐Acetyl Shift in a β,γ‐Unsaturated Ketone. Preliminary Communication
Authors: Sadler David E. , Hildenbrand Knut , Schaffner Kurt 
Published: December 2004

AbstractEnantiomerically enriched samples of 1,2‐dimethyl‐3‐(2H3)methyl‐2‐cyclopentenyl (1) and 1‐(2H3)methyl‐2,3‐dimethyl‐2‐cyclopentenyl methyl ketones (2) have been irradiated at 313 nm in methanol in the temperature range +50 to −45°. The 1,3‐acetyl shift, which interconverts the two isomeric ketones, occurs with a small change in the enantiomeric composition and independently of temperature in the range studied. This change corresponds to an upper limit of approximately 20% reaction with racemization. It is proposed that reaction occurs from both the S1(n, π*) and T2(n, π*) excited states with stereospecific reaction from S1 (rapid primary geminate recombination of a singlet radical pair, with a possible contribution by a concerted 1,3 shift) dominating throughout the temperature range, but with the proportion of reaction from T2 increasing as the temperature is lowered. The racemization results from secondary geminate recombination of the singlet and triplet radical pairs and the random recombination of free radicals. Viscosity effects are proposed to explain the independence of the racemization on temperature.
Carotenoids of the Carotenoprotein Asteriarubin. Optical Purity of Asterinic Acid
Authors: Bernhard Kurt , Englert Gerhard , Meister Walter , Vecchi Max , Renstrøm Britta , Liaaen‐Jensen Synnøve 
Published: December 2004

AbstractThe carotenoid composition of the carotenoprotein asteriarubin ex the starfish Asterias rubens, determined by HPLC, comprised canthaxanthin (6, 3% of total), all‐trans‐astaxanthin (1, 14%), all‐trans‐7,8‐didehydroastaxanthin (2, 24%), all‐trans‐7,8,7′,8′‐tetradehydroastaxanthin (3, 43%) and 4‐oxomytiloxanthin (7, 10%). The previously unknown 4‐oxomytiloxanthin was tentatively identified by the UV./VIS., 'H‐NMR. spectra and MS. data.The optical purity was determined by HPLC. of the di‐(−)‐camphanates, by comparison with those of synthetic standards: 7,8,7′, 8′‐tetradehydroastaxanthin (92% (3S, 3′S), 2% meso), 7,8‐didehydroastaxanthin (89% (3S,3′S), 2% meso?), and astaxanthin (78% (3S,3′S), 14% (3R,3′S), and 5% (3R,3′R)). It is concluded that the acetylenic derivatives of astaxanthin in contrast to astaxanthin from marine animal sources are essentially pure (3S, 3′S)‐isomers. This might reflect their probable metabolic formation by 4‐oxo modification of acetylenic (3R,3′R)‐carotenols ex Mytilus edulis in their diet.
Addition of Vinylketenes to Enamines. A Method for the Preparation of 6,6‐Dialkylcyclohexa‐2,4‐dienones and 4,4‐Dialkyl‐2‐vinylcyclobutenones
Authors: Berge John M. , Rey Max , Dreiding André S. 
Published: December 2004

Addition von Vinylketenen an Enamine. Eine Methode zur Herstellung von 6,6‐Dialkylcyclohexa‐2,4‐dienonenund4,4‐Dialkyl‐2‐vinylcyelobutenonenDrei Enamine (1–3) wurden mit fünf Vinylketenen (5a–5e) (s. Schema 2) zur Reaktion gebracht. Die Vinylketene wurden in situ durch HCl‐Eliminierung aus α,β‐ungesättigten Säurechloriden mit Triäthylamin hergestellt. Die Cycloadditionen von 1–3 an 5a–5e führten zu 6,6‐Dialkyl‐5‐dialkylaminoeyclohex‐2‐enonen (kurz: Cyclohexenone) bzw. zu 3‐Dialkylamino‐4,4‐dimethyl‐2‐vinylcyclobutanonen (kurz: Vinylcyclobutanone) oder zu einem Gemisch der beiden, je nach Natur der Partner bzw. des Lösungsmittels (s. Tab. 1). Durch oxydative Amin‐Eliminierung wurden die Cyclohexenone in 6,6‐Dialkylcyclohexa‐2,4‐dienone und die Vinylcyclobutanone in 4,4‐Dialkyl‐2‐vinylcyclobutenone übergefuhrt.Diese Reaktion stellt eine einfache Synthese von verschieden substituierten 6.6‐Dialkylcyclohexa‐2,4‐dienonen bzw. 4,4‐Dialkyl‐2‐vinylcyclobutenonen (siehe Schema 1) dar.
Nucleophilic addition to C, C‐double bonds. VI. Intramolecular addition of primary amines to C, C‐double bonds induced by steric compression
Authors: Tombo Gerardo M. Ramos , Ganter Camille 
Published: December 2004

AbstractThe tricyclic olefinic primary amine 1 readily cyclizes to the tetracyclic secondary amine 2 at approximately 200° in protic as well as aprotic solvents although the C, C‐double bond is not activated by electron‐attracting groups. This unusual intramolecular addition is the consequence of the close proximity of the nucleophile and the double bond.For the synthesis of the sterically highly hindered amine 1, the tricyclic oxime 4 was reduced with TiCl3 to the remarkably stable imine 5 and the latter treated with AlH3. On the other hand, reaction of 4 with AlH3 yielded the pentacyclic aziridine 6.
Enantioselective Synthesis of Pseudomonic Acids. I. Synthesis of Key Intermediates
Authors: Schönenberger Bernhard , Summermatter Walter , Ganter Camille 
Published: December 2004

AbstractAn enantioselective synthesis of key intermediates for the synthesis of the anti‐microbially active pseudomonic acids A (1), B (2) and C (3) is described. D‐Ribose (4) was used as starting material.
Synthesis of (±)‐Desmarestene and (±)‐Viridiene, the Two Sperm Releasing and Attracting Pheromones from the Brown Algae Desmarestia aculeata and Desmarestia viridis
Authors: Boland Wilhelm , Jakoby Karin , Jaenicke Lothar 
Published: December 2004

AbstractDesmarestene 1 6‐(1Z,3‐butadienyl)‐1,4‐cycloheptadiene and viridiene 3 cis‐3‐(1Z, 3‐butadienyl)‐4‐vinylcyclopentene are chemical messengers for male gametes of the brown algae Desmarestia aculeate and Desmarestia viridis. Total syntheses of 1, 3 and their stereoisomers 1a, 3a‐c are reported. Gas‐chromatographic comparison of synthetic 1 and 3 with the corresponding natural products has established their structural identity.
Photochemical Reactions 127th CommunicationPhotochemistry of Epoxy‐enones: Intramolecular Trapping of a Carbonyl Ylide
Authors: Ohta Shigeru , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractOn 1n, π* ‐excitation 5, 6‐epoxy‐2‐hydroxy‐5, 6‐dihydro‐β‐ionone ((E)‐4) shows the typical behaviour of a, β‐unsaturated γ, δ‐epoxy ketones undergoing primarily C(γ), O‐cleavage of the oxiran. However, 1π, π*‐excitation of (E)−4 leads to enol ether 10 which is formed by intramolecular insertion of the hydroxyl group of the ylide c.
Norbornanes. Part 10. Solvolysis of the Stereoisomeric 6‐Cyano‐2‐norbornyl p‐Toluenesulfonates. A Correction
Authors: Grob Cyril A. , Herzfeld Danielle 
Published: December 2004

AbstractThe solvolysis products of the stereoisomeric 6‐cyano‐2‐norbornyl p‐toluene sulfonates 1‐4 (R  CN) in dioxane/water 7 : 3 have been determined. In contrast to an earlier report the 6exo‐cyano‐2exo‐norbornyl p‐toluenesulfonate (1; RCN) yields 30% of the 2endo‐alcohol 9 (RCN) beside the 2exo‐alcohol 10 and the norbornenes 12 and 13. The results confirm that ‐ I substituents at C(6) reduce 1,3‐bridging in the intermediate norbornyl cation and hence its rate of rearrangement. The relatively high rate constants for some 6‐fluoro‐ and 6‐cyano‐2exo norbornyl p‐toluenesulfonates are ascribed to C, C‐hyperconjugation assisted by the conjugative effects of the 6‐fluoro and cyano substituents.
The Electronic Fine Structure of Co (11)‐Complexes with Schiff‐Base Ligands
Authors: Daul Claude , Weber Jacques 
Published: December 2004

AbstractMultiple‐scattering‐Xα MO‐calculations are reported for Co (acacen). The results are essentially in agreement with extended Hückel calculations and EPR. data. Particular emphasis has been placed on the calculation of the electronic structure and one‐electron properties, i.e. state energies diagram, spin‐orbit coupling and hyperfine coupling based on a ligand field interpretation of the Xα‐results, which allow to rationalize the main features of the EPR. spectra.
Spectroscopic Investigation of Anhydrous Solutions of Europium Perchlorate and Europium Nitrate in N, N‐Dimethylformamide
Authors: Bünzli Jean‐Claude G. , Yersin Jean‐Robert 
Published: December 2004

AbstractAnhydrous solutions of Eu(ClO4)3 and Eu (NO3)3 0.05m in N, N‐dimethyl formamide (DMF) are investigated by means of conductometric measurements, vibrational spectroscopy, electronic absorption and emission spectra, and fluorescence lifetime determinations. Eu (ClO4)3 is completely dissociated and no inner‐sphere interaction takes place between ClO4 and Eu3+ ions. The solvated species Eu (DMF) has a C2v‐symmetry and x is probably equal to 8.A more complicated situation occurs for Eu (NO3)3, the solutions of which contain at least three different solvates; the predominant species is [Eu (NO3)2 (DMF)x−4]+ (≈80% of the total Eu‐concentration) and it is more stable than the mononitrato complex [Eu (NO3) (DMF) X−2]2+; the neutral complex Eu (NO3)3 (DMF) x−6 is also present, as can be inferred from a high‐resolution analysis of the 5D0→7F0 emission band. The absence of emission from the excited 5D1‐level can be rationalized in terms of an efficient non‐radiative deexcitation path through a vibrational mode of the DMF‐molecules bonded to the central metal ion.
Cuprous complexes and dioxygen. IX. Formation of a unique trimeric species Cu3L and Ligand Oxidation (L  cis, cis‐1, 3, 5‐cyclohexanetriamine)
Authors: Szeverényi Zoltan , Knopp Ursula , Zuberbühler Andreas D. 
Published: December 2004

AbstractThe complexation of Cu+ by the potentially tripod like ligand cis, cis‐1, 3, 5 cyclohexanetriamine (chta) has been studied potentiometrically in aqueous acetonitrile (an). The expected tetracoordinated species Cu (chta) ⇌ (an)+ was formed only at rather high pH with log K (Cu (an)+ + chta ⇌ Cu (chta) · (an)+) = 6.94. Quite unexpectedly the most stable complex in neutral solution was the trimetric species Cu3 (chta) with log K (3 Cu+ + 2 chta ⇌ Cu3 (chta)) = 31.75. In addition, the ternary complexes Cu (LH2) · (an)3+ and Cu (LH) · (an)2+ (L = chta) are formed at low pH.From model considerations, Cu3 (chta) must contain two ligand molecules with all amino groups in equatorial position, linked by three linearly coordinated Cu+‐ions. Cu3 (chta)3+2 shows no measurable reactivity towards dioxygen. At pH values above 9, very rapid O2‐uptake due to Cu (chta) · (an)+ is observed. In this reaction, Cu+‐autoxidation is stoichiometrically coupled to ligand oxidation, followed by a much slower Cu‐catalyzed secondary reaction of the primary oxidation product of chta. Hydrogen peroxide and likely also superoxide, are involved in the coupled Cu+/ligand oxidation.
Verbascenin, ein macrocyclisches Spermin‐Alkaloid aus verbascum 184. Mitteilung über organische Naturstoffe
Authors: Seifert Karlheinz , Johne Siegfried , Hesse Manfred 
Published: December 2004

Verbascenine, a Macrocyclic Spermine Alkaloid Isolated from VerbascumThe new spermine alkaloid verbascenine (1) has been isolated from extracts of the aerial parts of Verbascum phoeniceum L. and V nigrum L. The structure of the alkaloid was elucidated by chemical degradation and by a study of the spectral properties of the alkaloid and its derivatives. Compared to the 13‐membered alter native 7 the 17‐membered structure 1 is preferred on the basis of mass spectral arguments.
Phototransformations of Some 2‐Substituted 4 H‐Chromen‐4‐ones (4‐Chromones) Related to the Antitumor Antibiotic Hedamycin
Authors: Fredenhagen Andreas , Séquin Urs 
Published: December 2004

AbstractThe 2‐substituted 4 H‐chromen‐4‐ones (4‐chromones) 2 and 3 have epoxysubstituted side chains at C(2) resembling that of the antibiotic hedamycin (1). They were chosen as model compounds and subjected to photolysis either in the presence or in the absence of oxygen. The products obtained were isolated by repeated HPLC., and their structures were determined by spectroscopic methods, mainly 1H‐ and 13C‐NMR. Especially noteworthy are the oxygen dependent formation of the tertiary alcohols 11 and 12 as well as the transformation of the diepoxychromone 3 to the allylic alcohols 13 and 14, the spiro compounds 15 and 16, and the 2‐ethylchromone 19.
Propellanes. LXVII. Reactions of 1, 6‐bridged [10]annulenes with 4‐methyl‐1,2,4‐triazoline‐3, 5‐dione
Authors: Ashkenazi Pnina , Vogel Emanuel , Ginsburg David 
Published: December 2004

AbstractReactions of 11‐substituted‐1, 6‐methano [10]annulenes and 1, 6‐methano [10]‐annulenes substituted in the aromatic ring with the title dienophile are described.
A New Route to the Synthesis of 2‐Amino‐6‐(methoxycarbonyl)amino‐4‐(tetrahydropyridyl)pyrimidine 1‐Oxide
Authors: Muller Jean‐Claude , Ramuz Henri , Wagner Hans‐Peter 
Published: December 2004

AbstractA new approach to 2‐amino‐6‐(methoxycarbonyl)amino‐4‐(1,2,3,6‐tetrahydro‐1‐pyridyl)pyrimidine 1‐oxide (3) is described. Methyl [1‐ethoxy‐2‐(ethoxycarbonyl)‐ethylidene]carbamate (5) reacted with guanidine to the pyrimidinecarbamate 6, which was successively transformed into methyl 2‐amino‐6‐(p‐tolyslulfonyl)oxy‐4‐pyrimidinecarbamate (8). Oxidation of 8 led to the corresponding pyrimidine N‐oxide 9, a useful starting material to 3.
Favorskii‐Reaktion von enolisierbaren Cyclobutanonen: Abhängigkeit der Stereoselektivität von der Abgangsgruppe, der Temperatur und dem Lösungsmittel
Authors: Martin Pierre 
Published: December 2004

Dependence of the Stereoselectivity on the Leaving Group, the Temperature and the Solvent in the Favorskii‐Reaction of Enolisable CyclobutanonesThe base‐induced contraction of enolisable 2‐halocyclobutanones is often not stereoselectiv. The cis/trans‐isomer ratio in the cyclopropanecarboxylic acid 9 derived from 2,4‐cis‐substituted cyclobutanones 7 depends on the nature of the leaving group. In addition, the choice of the base, the temperature and the solvent can profoundly affect the stereoselectivity of the Favorskii‐reaction. The use of the p‐bromophenylsulphonyloxy group as leaving group and an inhomogenous reaction medium leads exclusively to cis‐carboxylic acid 9.
Further Investigation of Grapefruit Juice Flavor Components (Citrus paradisi MACFAYDEN). Valencane‐ and Eudesmane‐type Sesquiterpene Ketones
Authors: Demole Edouard , Enggist Paul 
Published: December 2004

AbstractFourteen sesquiterpene ketones D–Q pertaining to the valencane (D–J) and eudesmane (K–Q) groups have been identified for the first time in grapefruit juice flavor. These novel grapefruit constituents, which include the six new compounds I, J, L, M, N and O, were identified by direct comparison with synthetic samples. Organoleptically, their total contribution to grapefruit flavor is not negligible. In particular, (+)‐8,9‐didehydronootkatone (E) has a powerful flavor with good grapefruit juice character.
Heterocyclole als Zwischenprodukte einer neuen, überraschenden Umlagerung bei der Reaktion von 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin mit monosubstituierten Parabansäuren. Vorläufige Mitteilung
Authors: Dähler Marlise , Prewo Roland , Bieri Jost H. , Heimgartner Heinz 
Published: December 2004

Cyclols as Intermediates in the Reaction of 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirine with Monosubstituted Parabanic Acids; a New and Unexpected RearrangementThe reaction of 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) with N‐methylparabanic acid (4) in 2‐propanol at room temperature gives the cyclol 5 in 97% yield. In acetonitrile solution 5 rearranges to the imidazoline derivative 6 (Scheme 2). The structures of the unexpected products 5 and 6 have been established by X‐ray crystallography.
Ru‐Catalyzed Oxidations with Iodosylbenzene Derivatives. Substituent Effects on Selectivity in Oxidation of Sulfides and Alcohols
Authors: Müller Paul , Godoy José 
Published: December 2004

AbstractOxidation of sulfides with PhIO/RuCl2 (PPh3)3 leads to sulfones. Electronwithdrawing substituents in the aromatic ring of PhIO reduce the reactivity and improves selectivity of the system. Thus, with m‐iodosylbenzoic acid sulfides are converted to sulfoxide. Under the same conditions aliphatic primary alcohols are transformed to aldehydes with m‐iodosylbenzoic acid, while PhIO affords carboxylic acids.
Absolute Configuration of Multifidene and Viridiene, the Sperm Releasing and Attracting Pheromones of Brown Algae
Authors: Boland Wilhelm , Mertes Karin , Jaenicke Lothar , Müller Dieter G. , Fölster Elsbet 
Published: December 2004

AbstractThe absolute configurations of the two algal pheromones multifidene1and viridiene2were determined as (+)‐(3S, 4S)‐3‐[(Z)‐1‐butenyl]‐4‐vinylcyclopentene and (+)‐(3R, 4S)‐3‐[(1Z)‐1, 3‐butadienyl]‐4‐vinylcyclopentene, respectively. The strategy involves enzyme‐initiated asymmetric synthesis of the ring‐saturated pheromone analogues (+)‐8aand (−)‐8band their subsequent catalytic hydrogenation to the chiral cycloalkanes9aand9b, only the letter of which is also obtained from the two natural messengers (+)‐1or (+)‐2. Biological activity assays proved these enantiomers of1or2to be the characteristic pheromones for male gametes of the seaweedsSyringoderma,Cutleria multifidaandChorda tomentosa.
Interaction of Enzyme with Polymer Matrix in Immobilized Enzymes
Authors: Kumakura Minoru , Kaetsu Isao 
Published: December 2004

AbstractThermolysin was immobilized by radiation polymerization of hydroxyalkyl acrylate and tetradecaethylene glycol dimethacrylate monomers at low temperatures in the presence of the enzyme, and the degree of interaction of the enzyme with the polymer matrix was studied by measuring the thermal stability of the immobilized enzyme. The thermal stability was affected by the molecular structure of the monomer; the thermal stability of the immobilized enzyme from hydrophilic monofunctional monomers in the wet state was higher than that from hydrophobic bifunctional monomers. The thermal stability in polymers formed from hydroxy‐alkyl acrylates decreased with an increase in the number of methylene units in the monomer, owing to a change of the state of the enzyme trapped in the porous polymer matrix. The enzyme molecule trapped in a hydrophilic porous polymer matrix appeared to be stabilized by interaction with the polymer chains.
Synthesen und chemische Reaktionen neuer Chinonderivate mit 1,6‐Methano[10]annulenpartialstruktur oder ihrer Valenztautomeren
Authors: Neidlein Richard , Martin Radke Christoph 
Published: December 2004

Syntheses and Chemical Reactions of New Quinone Derivatives with 1,6‐Methano[10]annulene Fragments or their ValencetautomersThe coupling of 2‐Methoxy‐1,6‐methano[10]annulene with aryldiazonium salts leads to the corresponding quinone hydrazones. These compounds undergo reduction with LiAlH4, condensation with hydrazines and hydrazides and alkylation at the carbonyl O‐atom or the hydrazone N‐atom.
Transition metal complexes with bidentate ligands spanning trans‐positions. Part XIV. Some complexes of 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene with platinum (0) and their reactivities
Authors: Boron‐Rettore Patrizia , Grove David M. , Venazi Luigi M. 
Published: December 2004

AbstractThe ligand 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene (1) has been used to prepare complexes of the type [PtL(1)] (L  C2H4, CH2CHCO2Me, PhCCPh, MeCCMe, MeO2CCCCO2Me, (i‐Pr)O2CCCCO2(i‐Pr), Ph3P and CO). It is shown that these complexes are less labile than the corresponding species [PtL(Ph3P)2]. The preparation of complexes trans‐[PtX(R)(1)] by oxidative addition of RX (RX  PhCH2Br and Mel) to [Pt(C2H4)(1)] is described. The isolation of [PtO2(CH3)2CO(1)] is also reported.
Photochemical reactions. 134th Communication. Photochemistry of 5,6‐epoxy‐5,6‐dihydro‐3,4‐methano‐β‐ionone: Influence of a cyclopropane ring on the reactivity of an ylide intermediate
Authors: Bischofberger Norbert , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractOn 1n,π*‐excitation(λ > 347 nm), the diastereomeric methanoepoxyenones (E)‐6 undergo isomerization via C,O‐cleavage of the oxirane leading to diastereomeric photoproducts ((E)‐5→(E/Z)‐13 and 14; (E)‐6→(E/Z)‐16 and 17). On 1π,π*‐excitation (λ = 254 nm) of either (E)‐5) or (E‐6 the photoproducts 9, 10 and 11 are formed. By laser flash photolysis (λ = 265 nm) the ylide intermediate 3 was detected, with a lifetime of 10 μs in MeCN at ambient temperature. Stern‐Volmer analysis of the ylide quenching by MeOH disclosed that compounds 9 and 10, but not 11, arise from the ylide intermediate e.
Die diastereomeren Mutatochrome. Trennung, absolute Konfiguration sowie chiroptische, spektroskopische und chromatographische Charakterisierung
Authors: Eschenmoser Walter , Märki‐Fischer Edith , Eugster Conrad Hans 
Published: December 2004

Diastereoisomeric Mutatochromes: Separation, Absolute Configuration, and Spectra and Chromatographic Behaviour(5S, 6R)‐5, 6‐Epoxy‐5, 6‐dihydro‐β, β‐carotent (2), prepared from azafrinal (1) was rearranged in an acid‐catalyzed reaction into the mixture of (5S, 8S)‐ and (5S, 8 R)‐5, 8‐epox‐5, 8‐dihydro‐β, β‐carotenes = ‘mutatochrome’. HPLC separation of the individual diastereoisomers led to the pure isomers for the first time. Their structures were assigned by analysis of the characteristic pattern of the signals of HC(7) and HC(8), respectively, in 1H‐NMR spectra. Although many reports of the occurrence of ‘mutatochrome’ exist, it is as yet not clear whether optically active or racemic forms predominate in nature. Combination of HPLC separations with UV/VIS and CD spectra should now allow an unambigous identification of the isomer in question.
(6′RS,8′RS,2E)‐ und (6′RS,8′SR,2E)‐3‐Methyl‐3‐(2y,2′,6′‐trimethyl‐7′‐oxabicyclo[4.3.0]non‐9′‐en‐8′‐yl)‐2‐propenal ([(5RS,8RS)‐ und (5RS,8SR)‐5,8‐Epoxy‐5,8‐dihydro‐ionyloinden]acetaldehyd): Synthese und Röntgenstrukturanalyse
Authors: Acemoglu Murat , Prewo Roland , Bieri Jost Hans , Eugster Conrad Hans 
Published: December 2004

Synthesis and X‐Ray Structure of (6′RS,8′RS,2E)‐ and (6′RS,8′SR,2E)‐3‐Methyl‐3‐(2′,2′,6′‐trimethyl‐7′‐oxabicyclo[4.3.0]non‐9′‐en‐8′‐yl)‐2‐propenal ([(5RS,8RS)‐ and (5RS,8SR)‐5,8‐Epoxy‐5,8‐dihydro‐ionylidene]acetaldehyde)To check our previous spectroscopic assignments of the structures of trans‐ and cis‐substituted furanoid end groups of carotenoid‐5,8‐epoxides, we now have synthesized the title compounds. An X‐ray structure determination of a single crystal of the trans‐isomer (±)‐‐10A is in agreement with the 1H‐NMR spectroscopic arguments: isomers with Δδ (HC(7), HC(8)) = 0.15–0.22 ppm and J > 1.4 for HC(7) belong to the cis‐series; Δδ in trans‐compounds is < 0.07 ppm, and HC(7) appears as a broad singulett.
1,6‐Eliminationsreaktionen an Spirocoleonon; Charakterisierung der ersten Spiro[(methylcyclopropan)‐phenanthren]‐1,3‐dion‐Derivate
Authors: Matloubi‐Moghandam Firouz , Rüedi Peter , Eugster Conrad Hans 
Published: December 2004

Preparation of the First Spiro[(methylcyclopropan)‐phenanthrene]‐1,3‐dione Derivatives by 1,6‐Elimination Reactions of SpirocoleonsSpirocoleons, e.g. coleon J (1), on treatment with 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN) in aprotic solvents, undergo enolization followed by a rapid 1,6‐elimination with formation of the hitherto unknown 2‐methyl‐spiro[cyclopropane‐1,2′(1′H)‐phenanthrene]‐1′,3′(4′bH)‐dione system, e.g. 3. In protic solvents, base‐catalyzed solvolysis of the spirocyclopropane predominates.