bluuebunny/crossref_metadata_2025_split huggingface dataset:
N(a)‐Demethylseredamin, ein neues Alkaloid aus Rauwolfia sumatrana; absolute Konfiguration von Seredamin. 140. Mitteilung über Alkaloide
Authors: Hanaoka M. , Hesse M. , Schmid H. 
Published: December 2004

AbstractFrom Rauwolfia sumatrana Jack (Apocynaceae) the two new indole alkaloids serpentinine and N(a)‐demethylseredamine were isolated. By chemical and spectroscopic evidence and by correlation experiments the latter was shown to have structure 2. the exact position of the aromatic methoxyl group was established by an investigation of the brominated derivative 12. The aromatic ORD. Cotton effect of N(a)‐acetyl‐N(a)‐demethyl‐seredamine (5) and its O‐acetyl derivative 4 as well as the ketone Cotton effect of purpeline (9) suggest that all the alkaloids of the seredamine group have the same absolute stereochemistry as ajmaline (1). This was confirmed by a direct chemical correlation of seredamine (7) with ajmaline.
Crystal and Molecular Structures of Benzylideneaniline, Benzylideneaniline‐p‐carboxylic acid and p‐methylbenzylidene‐p‐nitroaniline
Authors: Bürgi H. B. , Dunitz J. D. 
Published: December 2004

AbstractThe structures of the title compounds have been established by X‐ray crystal structure analysis, based on three‐dimensional diffractometer data. Bond lengths and angles are given, and the thermal motion of the molecules in the crystals is discussed. The most striking feature of all three molecules is the twist of the aniline ring out of the CNCC plane by 41–55°.
Zur Biogenese des Antibioticums Phomin. 1. Teil: Die Grundbausteine
Authors: Binder M. , Kiechel J.‐R. , Tamm Ch. 
Published: December 2004

AbstractA number of potential 14C‐ and 3H‐labelled precursors were fed to growing cultures of Phoma spec. (Strain S 298), after the rate of formation of phomine (cytochalasin B; C29H37NO5) had been determined. By chemical degradation of [14C]‐phomine and [3H, 14C]‐phomine the distribution of the radioactivity originating from the incorporated precursors was determined. The results demonstrate that the building blocks of phomine are 1 unit of phenylalanine, 9 units of acetate or malonate respectively, and 2 units of methionine. Acetate acts as a starter and malonate as a propagator of a C16‐ or C18‐chain. A possible combination of these elements leading to phomine and to 5‐dehydrophomine is suggested.
Aminofuroxane. 1. Synthese und Struktur
Authors: Gagneux André R. , Meier René 
Published: December 2004

AbstractPhenylglyoximes are transformed in a single operation into 3‐amino‐4‐phenyl‐furoxans which rearrange quantitatively to their 3‐phenyl‐4‐amino‐isomers above 80°. A mechanism for the synthesis is proposed and supported by the isolation of intermediates. Proof for the structure of both furoxan isomers and intermediate phenylaminoglyoximes rests on chemical transformations, mechanistic considerations, and the influence of certain structural changes on the UV.‐ spectra.
Allylic Oxidation of some 5,6‐Unsaturated Steroids with Lead Tetraacetate. Communication XXII on reactions with lead tetraacetate
Authors: Stefanović M. , Jokić A. , Maksimović Z. , Lorenc Lj. , Mihailović M. Lj. 
Published: December 2004

AbstractOxidation of cholesteryl acetate and diosgenyl acetate with lead tetraacetate in benzene or glacial acetic acid solution results in allylic acetoxylation in the C‐7 position. These reactions are nonstereospecific, and in both solvents mixtures of the corresponding 7β‐ and 7α‐epimeric acetoxy derivatives are formed. On the basis of the results, the mechanism of this oxidation reaction is discussed.
Organische Phosphorverbindungen 41. Synthese und Eigenschaften von Polyphosphinaten und Polyphosphinsäuren [1]
Authors: Maier Ludwig 
Published: December 2004

AbstractA process for the preparation of alkyl chloromethylphosphonites, ClCH2P(OR)2 (R = Et, Bu), diethyl β‐chloroethylphosphonite, ClCH2CH2P(OEt)2, and their conversion to polyphosphinates with the back‐bone structures [CH2PO2R]x and [CH2CH2P(O2R)]x, respectively, by an Arbuzov type reaction is described. Hydrolysis to the corresponding polyphosphinic acids is effected by refluxing the esters with conc. HCl for extended periods. The polyphosphinic acid with structure V is an excellent chelating agent for Ca ions.
Organische Phosphorverbindungen 42. Einige Reaktionen von Bis‐(dialkoxyphosphonyl‐methyl)‐O‐alkylphosphinaten und Tris‐(dialkoxyphosphonyl‐methyl)‐phosphinoxiden [1]
Authors: Maier Ludwig 
Published: December 2004

AbstractThe metallation of alkyl bis‐(dialkyloxyphosphonyl‐methyl)‐phosphinates (I) and tris‐(dialkyloxyphosphonyl‐methyl)‐phosphine oxides (II) proceeds quantitatively with Na, K, or NaH in inert organic solvents. Alkylation of these metallated derivatives is effected with alkyl halides. In addition to the mono‐alkylated products, the di‐alkylated and the non‐alkylated products are formed also.The ester groups of II can be replaced by aryl groups by reaction with Grignard reagents to produce the corresponding tetratertiary phosphine oxides.Reduction of II with LiAlH4 results in complete rupture of the molecule and produces only the cleavage products PH3 and CH3PH2. Chlorination of the ester groups of I and II does not lead to uniform products. Concomitant with the chlorination of the ester groups, a cleavage reaction has been observed which produces as the main product Cl2CHP(O)Cl2.The anhydride of the hexa‐acid of II is readily obtained either by reaction of this acid with (CH3CO)2O or by reaction of II with (PhCO)2O. The titration behaviour and the high m. p. indicate an adamantane‐like structure for the anhydride.Halogenation of the bridging PCH2P groups of I and II is achieved by reaction with aqueous alkaline hypohalite at ambient temperature. This halogenation is accompanied by partial cleavage, and analytically pure samples could not be isolated.
Stoffwechselprodukte von Mikroorganismen. 89. Mitteilung [1]. Synthese von zwei diastereomeren 2, 4, 6‐Trimethylpimelinsäuren. Ein Beitrag zur Stereochemie des Borrelidins
Authors: Keller‐Schierlein W. , Brufani M. , Muntwyler R. , Richle W. 
Published: December 2004

AbstractBy conventional methods a mixture of diastereomeric 2,4, 6‐trimethylpimelic acids was prepared and separated by counter‐current distribution. The two meso‐compounds were isolated in crystalline form, one of them (m.p. 130°) giving a dimethyl ester identical with a degradation product of the antibiotic borrelidin. The chirality (2‐R,4‐r,6‐S) of the acid of m.p. 130° was determined by an X‐ray structural analysis (see following paper).
Über siliciumaromatische Verbindungen. III. Trimethylsilyl‐ und Triphenylsilyl‐substituierte Farbstoffe der Anthrachinonreihe
Authors: Hopff H. , Deuber J. M. , Gallegra P. , Said A. 
Published: December 2004

AbstractThe influence of the presence of trimethylsilyl and triphenylsilyl groups in substituents of anthraquinone on the properties of anthraquinone vat, acid, and dispersion dyes was investigated.
Autumnariol und Autumnariniol, zwei neue Dibenzo‐α‐pyrone aus Eucomis autumnalis Graeb. Nachweis einer Fernkopplung über sechs Bindungen in den magnetischen Protonenresonanz ‐ Spektren
Authors: Sidwell W. T. L. , Fritz H. , Tamm Ch. 
Published: December 2004

AbstractFrom bulbs of Eucomis autumnalis Graeb (Liliaceae) autumnariol (1) and autumnariniol (4), two new substituted dibenzo‐α‐pyrones have been isolated. Their structures have been determined mainly using spectroscopic techniques. In the NMR. spectra of 1 and 4 and related model compounds an unusuallong‐range coupling over six bonds has been demonstrated.
Stereoselective Effects in Reactions of Metal Complexes, II selectivity in the complex formation of nickel(II)‐, copper(II)‐and zinc(II)‐(D)‐propylenediaminetetraacetate with racemic 1‐phenylethyl‐amine [1]
Authors: Bernauer K. , Jeanneret M.‐F. , Vonderschmitt D. 
Published: December 2004

AbstractThe selectivity in the formation of mixed complexes of optically active metapropylenediaminetetraacetates with 1‐phenylethyl‐amine has been investigated by chromatography and by liquid‐phase distribution measurements for the three metal ions Ni2+, Cu2+ and Zn2+. The selectivity is found to be sufficiently high to allow the chromatographic resolution of the racemic amine.
Préparation de quelques dérivés du nitro‐5‐thiophénecarbaldéhyde‐2
Authors: de Malleray Bernard Miche 
Published: December 2004

AbstractDeux nitro‐thénylidéne‐oxazolones obtenues à partir du nitro‐5‐thiophénecarbaldéhyde‐2 ont été réduites et acétylétylées en une seule étape en méthyl‐2‐(acétylamino‐5‐thénylidène‐2)‐4‐oxazolone‐5 et en phényl‐2‐(acétylamino‐5′‐thénylidène‐2′)‐4‐oxazolone‐5 respectivement, déjà obtenues par une autre voice [1].
Note sur la préparation de l'acétylamino‐5‐acéty‐2‐thiophène
Authors: de Malleray Bernard Miche 
Published: December 2004

AbstractL'acétylamino‐5 acétyl‐2‐thiophéne a été préparé avec un bon rendement par traitement de l'acéatylamino‐5‐thiophène (obtenu è partir du thiophéne par des procèdés connus) par Tanhydride acétique en présence de faibles quantités d'acide perchlorique.
ESR. Spectra of the Radical Anions of Cycloalkylbenzenes
Authors: Gerson F. , Moshuk G. , Schwyzer M. 
Published: December 2004

AbstractRadical anions of five cycloalkylbenzenes (alkyl = propyl, butyl, pentyl, hexyl, or heptyl) have been studied by ESR. spectroscopy at −90°C. In the case of cyclopropylbenzene, no reliable experimental data could be obtained, because of the instability of its radical anion. The spectra of the radical anions of the four higher homologues have been analysed by means of a computer program. The assignment of the coupling constants to the α‐protons in the para position of the benzene ring and to the cycloalkyl ß‐protons has been based on the spectra of specifically deuterated derivatives.The experimental data of the radical anion of cycloalkylbenzenes have been compared with those of the radical anions of five alkylbenzenes (alkyl = methyl, ethyl, n‐propyl, isopropyl, or t‐butyl), the spectra of the latter being reexamined at −90°C. In the cycloalkyl series the degeneracy of the two benzene‐type lowest antibonding orbitals is the more effectively removed the larger the substituent, whereas the reverse relation holds for the non‐cyclic series. The preferred conformation of the substituents is that in which the alkyl or cycloalkyl ß‐proton is near to the nodal plane of the benzene π‐system, and this preference is accentuated with the increasing size of the substituent group.
Photoelectron‐Spectroscopic Evidence for the Orbital Sequence in Fulvene and 3, 4‐Dimethylene‐cyclobutene
Authors: Heilbronner E. , Gleiter R. , Hopf H. , Hornung V. , De Meijere A. 
Published: December 2004

AbstractThe photoelectron spectra of fulvene (II) and of 3,4‐dimethylene‐cyclobutene (III) have been recorded. The PE. bands are correlated, in order of increasing ionisation potentials, with the following orbitals: II: 1a2(π), 2b1(π), 7b2(π), 1b1(π); III: 2b1(ω), 1a2(π), 10a1(ω), 8b2(ω), 1b1(π). This assignment is based on a semi‐quantitative perturbation MO‐model and on the SCF‐LCAO‐MO calculations reported by Praud, Millie & Berthier [5] for benzene, II and III.
Welkstoffe und Antibiotika. 39. Mitteilung [1]. Fusarinolsäure
Authors: Steiner K. , Graf U. , Hardegger E. 
Published: December 2004

AbstractDas als Substanz H bezeichnete biologische Umwandlungsprodukt der Fusarinsäure (I) wurde als S(+)‐Fusarinolsäure (VIII) erkannt. Beweisend für die Konstitution VIII war die Umwandlung der Dehydrofusarinsäure (V) über die rac.‐Fusarinolsäure (Ia) in das (+)‐Fusarinolsäure‐(+)‐camphersulfonat (VIIIa), welches mit einem aus natürlicher (+)‐Fusarinolsäure (VIII) hergestellten Präparat identisch war. Die S‐Konfiguration der natürlichen (+)‐Fusarinolaäure ergab sich aus der Synthese von VIII bzw. VIIIa aus der Dinatriumverbindung VI des 2‐Carboxy‐5‐methyl‐pyridins and S(+)‐2‐Benzyloxy‐propyljodid (VIIa), welches konfigurativ mit der L‐Milchsäure verknüpft wurde.
Chemically Induced Dynamic Nuclear Polarization VIII: Thermal decomposition of dibenzoyl peroxides in solution [1]
Authors: Blank B. , Fischer H. 
Published: December 2004

AbstractThermolysis of di‐(4‐chlorobenzoyl)‐peroxide was carried out in the probe of an NMR. spectrometer. The dependence of product distribution and chemically induced dynamic nuclear polarization (CIDNP.) patterns on the concentrations of radical trapping agents gives evidence that the CIDNP. effects are caused by singlet‐triplet transitions, dependent on nuclear spin, in transient benzoyloxy/phenyl radical pairs and by the selective formation of radical products from singlet state pairs.
Synthèses dans la série des bis‐indéno‐anthracènes, II [1] Le dihydro‐9,16‐bis‐indéno[2.1‐α; 1′,2′‐c]anthracène
Authors: Chardonnens Louis , Schorderet François 
Published: December 2004

AbstractStarting from 3,3′‐bi‐indenyle and 1,4‐naphthoquinone the title compound, III, has been synthesized in 3 steps (overall yield 54.6%).
Tetrakis‐triphenylphosphin‐platin(0), ein Katalysator zur selektiven Hydrosilylierung
Authors: Fink Walter 
Published: December 2004

AbstractTetrakis‐triphenylphosphine‐platinum(0) catalyses selectively the addition of silane to terminal olefinic double bonds. Neither hydrosilylation of internal double bonds nor isomerisations occur with this catalyst.
Synthese und Biologische Auswertung von 3β,20(R)‐Dihydroxy‐Protost‐24‐en
Authors: Immer H. , Huber K. 
Published: December 2004

AbstractThe possible lanosterol precursor, 3β, 20(R)‐dihydroxy‐protost‐24‐ene (1 a) has been prepared, in thirteen steps, from 3α‐hydroxy‐4α, 8, 14‐trimethyl‐18‐nor‐5α, 8α, 9β, 13ξ, 14β‐androstan‐17‐one (mixture of 2 and 3). In vitro experiments with rat liver homogenates failed to convert 1 a to lanosterol.
p‐Azido‐L‐phenylalanine: A photo‐affinity ‘probe’ related to tyrosine
Authors: Schwyzer Robert , Caviezel Mario 
Published: December 2004

AbstractSynthese und Eigenschaften des p‐Azido‐L‐phenylalanins (1) und einiger seiner für die Peptidsynthese geeigneter Derivate werden beschrieben. Infolge der photolytischen Spaltbarkeit in Stickstoff und das Imen 2 dürfte dieses Analogon des Tyrosins als «photochemische Affinitätssonde» verwendbar sein.
The Competition between Spin Orbit Coupling and Conjugation in Alkyl Halides and its Repercussion on their Photoelectron Spectra
Authors: Brogli F. , Heilbronner E. 
Published: December 2004

AbstractA crude molecular orbital model for alkyl halides is proposed, which provides a semi‐quantitative rationalization for the following experimental observations: (a) In the photoelectron spectra of alkyl halides RX (symmetry C8) the lone pair band is split into two components, separated by a gap Δ. This gap is equal to the splitting associated with spin‐orbit coupling in systems where X lies on a symmetry axis of order n ≥ 3. (b) The vibrational pattern of the two components indicates substantial conjugation between R and X. (c) Notwithstanding (b), the gap Δ is largely independent of the type of alkyl group R. (d) For strongly conjugating alkyl groups (e. g. R = cyclopropyl) the first component of the lone pair band (i. e. the one at lower ionization potential) broadens while the one at higher potential sharpens up.
Organic Phosphorus Compounds 52. Preparation and properties of β‐hydroxyalkyl‐phosphonium salts and tertiary phosphine oxides
Authors: Maier Ludwig 
Published: December 2004

AbstractThe new, tris‐ (2‐ hydroxyalkyl) ‐ (hydroxymethyl) ‐ phosphonium salts: [(RCHOHCH2)3PCH2OH]Cl (I, R = ClCH2; III, R = CH3) are formed in high yield by reaction of tetrakis‐(hydroxymethyl)‐phosphonium chloride (Tetrakis) with epoxides under basic conditions. Under the same conditions, styrene oxide yields only the disubstituted product, [(PhCHOHCH2)2(CH2OH)2P]Cl. Optimal pH values for the reactions are 8 to 9; at lower pH the conversion is too slow; at a higher pH, oxidative decomposition of the salts occurs. Conversion of the salts to tertiary phosphine oxides (RCHOHCH2)3P  O (R  ClCH2; CH3) with loss of the hydroxymethyl group is best carried out with chlorine at pH 5 to 7. The yields are usually 60 to 90%.
Réactions d'élimination présentées par des acides polyhydroxyadipiques
Authors: Gabbai A. , Posternak Th. 
Published: December 2004

AbstractThe tetrahydroxyadipic acids and one trihydroxyadipic acid have been methylated, using methyl iodide and silver oxide in the presence of dimethylformamide.In addition to Δ2‐di‐ or tri‐methoxyadipic esters and the products expected for a double E2 elimination, cis‐trans α, α'‐dimethoxymuconic ester was frequently the principal product. The proposed theoretical interpretations involve as intermediates either a silver complex or a lactonic compound. A few preferential conformations, based on NMR. data, are proposed.
Protonierung von Purin, Adenin und Guanin NMR.‐Spektren und Strukturen der Mono‐, Di‐ und Tri‐Kationen
Authors: Wagner R. , Von Philipsborn W. 
Published: December 2004

AbstractProton NMR. spectra of purine, adenine, guanine and methylsubstituted guanines have been measured in CF3COOH, FSO3H and FSO3HSbF5SO2 at 27° and low temperatures. These conditions permit to study multiple protonation of purines, using chemical shifts of CH, NH and OH protons. The spectra of mono‐, di‐ and tri‐cations are described and fully assigned.
On the correlation between photoelectron and electronic spectra in trans‐ azomethane
Authors: Haselbach E. , Schmelzer A. 
Published: December 2004

AbstractA possibility of correlating electronic and photoelectron spectra is discussed, using trans‐azomethane as an example. The Coulomb and exchange integrals required were obtained by three semi‐empirical SCF‐methods: MINDO/2, CNDO/2, and a modified CNDO method. The orbital energies were taken as minus the corresponding experimental ionization potentials. The sequence of the transition energies ΔE (ns → π*) Δ E (na → π*) < ΔE (π → π*) is found to be different from the ionization potential sequence IP (ns) < IP (π) < IP (na), in agreement with previous spectroscopic studies; the results support the latest view that the π → π* transition of the azo group occurs at around 12 eV.
Isomérisations en chimie des sucres. II Fermetures de cycles par attaque nucléophile intramoléculaire sur des carbones sp2 à caractère électrophile: Furannoses hybridés sp2 en C3
Authors: Tronchet J. M. J. , Bourgeois J. M. 
Published: December 2004

AbstractWhen heated with one equivalent of H2O, the 1,2: 5,6‐di‐O‐isopropylidene‐α‐D‐ribo‐ and ‐xylo‐hexofuranos‐3‐uloses loose one molecule of acetone and yield the 3, 6‐anhydro‐1, 2‐O‐isopropylidene‐α‐D‐ribo‐ and ‐xylo‐hexofuranos‐3‐ulose ketohydrols. The carbonyl group of the starting material seems to provide some kind of intramolecular electrophilic assistance to the hydrolysis of the 5, 6‐O‐isopropylidene group. When the oxygen of the carbonyl group is replaced by cyanomethylene, an analogous cyclisation takes place under base catalysis, provided that C6 bears a free hydroxyl group.
Hexamethyl‐2‐oxabicyclo [3.2.0] hepta‐3,6‐dien
Authors: Baumann B. C. , Rey M. , Markert J. , Prinzbach H. , Dreiding André S. 
Published: December 2004

AbstractSubstance X, one of the three compounds obtained upon heating 5, 6‐endo‐epoxy‐hexamethyl‐bicyclo[2.2.0]hex‐2‐ene (11) and previously postulated by Klaus et al. [10] to be 5‐acetyl‐pentamethyl‐bicyclo[2.1.0]pentene (9), is now shown to be hexamethyl‐2‐oxabicyclo[3.2.0]‐hepta‐3, 6‐diene (10) by reinterpretation and supplementation of the spectral data and by ozonization of the dihydro derivative 16, which yields 1‐acetoxy‐2‐acety‐1‐1, 2, 3, 4‐tetramethyl‐cyclo‐butane (17). It is concluded that the Claisen equilibrium in this system lies entirely on the side of the enol ether 10; even drastic LiAIH4 conditions cannot force a reversal (10 → 9). Tetracyanoethylene adds to the enolic double bond of 10 to form the cyclo‐adduct 19.
On the chirality of the cystine disulfide group: Assignment of helical sense in a model compound with a dihedral angle greater than ninety degrees using NMR. and CD
Authors: Ludescher Urs , Schwyzer Robert 
Published: December 2004

AbstractIm synthetischen [2, 7‐Cystin]‐Gramicidin S ist der Cyclodecapeptid‐Ring mit einer Disulfidgruppe überbrückt. NMR.‐Untersuchungen zeigen, dass die Peptidkette der Verbindung (wie beim Gramicidin S) in der antiparallelen β‐Konstellation vorliegt. Auf Grund von Abschirmungs‐Effekten kann der Disulfid‐Brücke die P‐helikale Chiralität zugewiesen werden. In Molekel‐Modellen beträgt der dihedrale Winkel φ etwa 120°. Die P‐helikale Anordnung, verbunden mit |90°| < |φ| < 180°|, bedingt nach der Theorie von Linderberg & Michl einen negativen Rotationsbeitrag der langwelligsten asymmetrischen Absorptionsbande, was mit unseren CD.‐Versuchen nun erstmals experimentell bestätigt wird (λmin = 271,5 nm, Θ = ‐7550, Åthanol). Auch der theoretisch geforderte zweite Cotton‐Effekt mit umgekehrtem Vorzeichen kann bei dieser Modellverbindung gut beobachtet werden (λmax = 230 nm, Θ = +60870, Åthanol); allerdings sind in diesem Bereiche Beiträge von Peptid‐n → π*‐Übergängen nicht a priori auszuschliessen, was den diagnostischen wert dieser Bande vermindert.
Recherches dans la série des cyclitols XLII. Synthèses de cyclitols tout‐cis dérivés du cyclopentane; préparation des cyclopentane‐tétrol et ‐ pentol tout‐cis
Authors: Cocu F. G. , Posternak Th. 
Published: December 2004

AbstractAll‐cis cyclitols derived from cyclopentane have been prepared in two ways: (i) by LiAlH4 reduction of all‐cis epoxypolyos; (ii) by dimethyl sulfoxide treatment, in the presence of sodium hydrogencarbonate, of brominated derivatives containing a neighbouring benzoyloxy group; under these conditions, the halogen is replaced by a cis‐oriented hydroxyl group. Thus all‐cis cyclopentane‐tetrol and ‐pentol have been prepared; their configuration has been confirmed by NMR. spectroscopy.
Synthèse du méthanesulfonate de (pyrimidyl‐2)‐1‐(méthylène)‐(dioxy‐3, 4‐benzyl)‐4‐pipérazinium (Piribedil) marqué au 14C
Authors: Lintermans J. , Benakis A. , Herbert M. , Pichat L. 
Published: December 2004

AbstractThe synthesis of crystalline 1‐(2‐pyrimidyl)‐4‐(3, 4‐methylenedioxybenzyl)‐piperazin methanesulfonate (ET 495) labelled with 14C fixed on the piperazine nitrogen N(4) has been realized in five steps from barium carbonate 14C; Specific activity of the final product: 32,8 mCi/mmol (110 m̈Ci/mg); radiochemical purity: around 99%. The mass spectrum of the labelled compound is in agreement with the chemical structure and the labelling position expected.
Action de nucléophiles sur des sucres ramifiés cyanovinylidéniques: Addition conjuguée, stéréomutation, migration de doubles liaisons. Communication préliminaire
Authors: Tronchet J. M. J. , Bourgeois J. M. 
Published: December 2004

AbstractWhen treated with a series of nucleophiles cis‐3‐cyanomethylene‐3‐deocy‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐ribo‐hexofurannose (1) may yield its trans isomer, a product of allylic isomerization or a product of conjugate addition, depending on the nature of the nucleophile. The configuration of the starting material is also important as shown by the differences in reactivity between 1 and its trans‐xylo isomer 8.
Mass Spectrometry and Organic Analysis, part 14. The photolysis and mass spectra of medium and large ring ketones from C9 to C16
Authors: Schulte‐Elte K. H. , Willhalm B. , Thomas A. F. , Stoll M. , Ohloff G. 
Published: December 2004

AbstractThe photolysis of cyclic ketones from C9 to C16 has been carried out, and formation of cyclobutanols observed in only C11 to C16. Although in the mass spectrometer cyclobutanols are not formed, an initial transfer of a γ‐hydrogen atom to the carbonyl group is shown to occur in the mass spectra of all cyclic ketones higher than C10.