bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption and Fluorescence Studies on Neutral and Cationic Isoalloxazines
Authors: Visser Antonie J. W. G. , Müller Franz
Published: December 2004

The electronic properties of a variety of methylated isoalloxazine derivatives have been investigated with absorption and fluorescece techniques (Table 1). The spectral effects of methyl substitution at different positions in the isoalloxazine ring are interpreted in terms of different bond orders between the C‐atoms of the methyl groups and of the aromatic ring. Methyl groups at C(6) or C(9) induce quenching of the fluorescence and shortening of the lifetime whereas a methyl group at C(7) has an opposite effect. The quenching effect might be due to strain in the molecular framework caused by the methyl groups.

The lowest energy levels of the isoalloxazine cations are shifted to higher energy as compared to the neutral isoalloxazines. Apart from these shifts the trends in spectral behaviour upon methylation are similar to those observed for the neutral isoalloxazine (cf. Table 2). The fluorescence of the isoalloxazine cations is strongly quenched in auqeous solution and their lifetime much shortened. These observations indicated that there is substantial interaction between the charged fluorophore and the water dipoles and that this interaction produces efficient radiationless deactivation of the first excited singlet state.
Structure of Globularidin: An Unusual Iridoid Glucoside from Globularia alypumL.
Authors: Chaudhuri Ratan Kumar , Sticher Otto
Published: December 2004

A novel iridoid glucoside, named globularidin, lacking the typical double bond between C(3) and C(4), has been isolated from the whole plant of Globularia alypum by the combination of open column‐ and high‐performance liquid chromatography. The structure of this compound was established by chemical transformation and spectral data.
15N‐NMR. and 31P‐NMR. Studies of palladium and platinum complexes
Authors: Motschi Herbert , Pregosin Paul S. , Venanzi Luigi M.
Published: December 2004

15N‐NMR. parameters for the complexes trans‐[MCl2 (15NH2 (CH2)5CH3)L] are reported; M = Pt, Pd, L = PBu, PMePh2, P (p‐CH3C6H4)3, AsBun3, AsMePh2, As (p‐CH3C6H4)3, NH2 (CH2)5CH3 and (for Pt) C2H4. For both metals, the NMR. parameters depend on the trans‐influence of the ligand L. The values 1J (195Pt, 15N) vary from 138 to 336 Hz and can be shown to correlate with the values 1J (195Pt, 31P) in the complexes trans‐[PtCl2 (PBu)L]. There is a linear relation between the 15N chemical shifts in the complexes of the two metals. The reactions of the complexes sym‐trans‐[M2Cl4L2], M = Pd, Pt, L = a tertiary phosphine or arsine, with neutral ligands are described. 195Pt‐, 31P‐ and 13C‐NMR. data are reported.
Synthèse et désamination enzymatique des C‐hydroxyméthyl‐3′‐ et C‐méthyl‐3′‐β‐D‐xylofurannosyl‐9‐adénines
Authors: Tronchet Jean M. J. , Tronchet Jeannine F.
Published: December 2004

Synthesis and enzymatic deamination of 3′‐C‐hydroxymethyl‐ and 3′‐C‐methyl‐β‐D‐xylofuranosyl‐9‐adenines

The title compounds have been prepared by classical synthetic steps after having optimized the nature of the blocking groups. Both nucleosides were found to be substrates of adenosine aminohydrolase which proved that C(3′)‐branched‐chain sugar nucleosides can be deaminated when the branched‐chain is exo (trans relative to the base) if a suitably disposed hydroxy group is available on the endo side of the furanose ring.
Kinetische Betrachtung der Verteilung von elektrisch neutralen Ionophoren zwischen einer Flüssigmembran und einer wässerigen Phase
Authors: Oesch Urs , Simon Wilhelm
Published: December 2004

Kinetic Study of the Distribution of Electrically Neutral Ionophores between a Solvent Polymeric Membrane and an Aqueous Phase

The kinetic behaviour of a series of ligands in the transfer from a solvent polymeric membrane into a stirred aqueous phase was investigated and compared with theoretical kinetic models. It was found that the transfer of ligands with low lipophilicity was controlled by the diffusion in the membrane phase, and that of ligands with high lipophilicity was controlled by the exchange reaction at the phase boundary and/or the diffusion through the unstirredNernstdiffusion layer. The diffusion coefficients in the membrane decrease drastically on increase of the content of the polymer in the membrane and are nearly independent of the size and lipophilicity of the ligand, whereas the overall transfer coefficient through the boudary region does not depend on the polymer content but decreases with increasing lipophilicity of the ionophore.
Photooxygenation of 3,3‐dialkylsubstituted allyl alcohols. Occurrence of syn preference in the ene addition of 1O2 at E/Z‐isomeric allyl alcohols
Authors: Schulte‐Elte Karl H. , Muller Bernard L. , Pamingle Hervé
Published: December 2004

Dye‐sensitized photooxygenation (1O2‐reaction) of the symmetrically 3,3‐dialkyl‐substituted allyl alcohols 1–6 (A, Table 1) and the E‐ and Z‐isomers of the 3‐methyl‐3‐alkylsubstituted allyl alcohols 7–11 (A1, Table 2) has been studied. The α, β‐epoxyaldehydes B and B1 and the β‐hydroperoxy‐homoallyl alcohols C, C1 and D1 were practically the sole oxygenation products formed. The rate and selectivity of the 1O2 additions were found to be markedly dependent on the degree of substitution (i.e. H‐availability) at the allyl position which is Z‐orientated to the carbinol group. The allyl alcohols with a Z‐3‐methyl group, 1 and the E‐isomers of 7 to 10, showed practically the same reactivity towards 1O2 and formed only the two oxygenation products of type B1 and C1 (ratio close to 60:40). In contrast, the allyl alcohols with a Z‐3‐methylene group, 2 and the Z‐isomers of 7 to 9, reacted more slowly with 1O2 and yielded all the three possible products B1, C1 and D1 in a very different ratio of ∼ 80:10:10. However, from both the E‐ and Z‐isomers of the alcohols 7 to 10 the formations of the two oxygenation products were always strongly favoured (85–100%) which result from 1O2 additions at the disubstituted side of the double bond. This behaviour is thus completely analogous to that of the corresponding trisubstituted olefins previously studied [1]

The same side‐specific selectivity in 1O2 ene additions to several E/Z‐isomeric and deuterium‐labelled olefins has also been described recently by C.M. Stephenson et al. [2] (we thank Dr. V. Rautenstrauch and Prof. C.W. Jefford for informing us about this work). The similar behaviour of enol ethers, which react with 1O2 preferentially at the RO‐substituted side, had been observed earlier by C.S. Foote et al. [3] and extended to numerous derivatives by J.M. Conia et al. [4] [5].

and follows a new selection rule, termed syn‐preference [1], in the ene addition of 1O2.
Thermische Cyclisierung von α‐Alkinonen zu 2‐Cyclopentenonen
Authors: Karpf Martin , Dreiding André S.
Published: December 2004

Thermal Cyclization of α‐Alkynones to 2‐Cyclopentenones

Gas phase thermolysis at 600–740° of substituted 1‐pentyn‐3‐ones (α‐alkynones), which are easily prepared by acylation of trimethylsilyl acetylenes, leads to substituted 2‐cyclopentenones. The intramolecular formation of a new C, C‐bond between an acetylenic and a non‐activated carbon atom is accompanied by a [1,2]‐migration of one of the substituents at the triple bond. This novel ‘‐alkynone cyclization’ reaction may be explained by postulating an alkylidene carbene intermediate which inserts into a C,H‐bond five carbon atoms away at the non‐acetylenic part of the ketone. Several examples demonstrate that the α‐alkynone cyclization offers a simple tool for the preparation of certain monocyclic, bicyclic and spiro compounds containing a 2‐cyclopentenone moiety.
The Synthesis of [4‐Carboranylalanine, 5‐Leucine]‐Enkephalin (Including an Improved Preparation of t‐Butoxycarbonyl‐L‐o‐carboranylalnine, New Derivatives of L‐Propargylglycine, and a Note on Melanotropic and Opiate Receptor Binding Characteristics)
Authors: Fauchère Jean‐Luc , Leukart Othmar , Eberle Alex , Schwyzer Robert
Published: December 2004

The title compound, an analogue of [Leu5]‐enkephalin with L‐o‐carboranylalanine replacing L‐phenylalanine in position 4, was prepared by fragment condensation. The analogue has a 3‐fold higher affinity for rat brain opiate receptors in the [3H]naloxone competition assay than natural [Leu5]‐enkephalin. Like [Leu5]‐enkephalin and Na‐acetyl‐[Leu5]‐enkephalin, the N‐terminal tripeptide fragment, H · Tyr‐Gly‐Gly · OH, had no melanotropic activity in the Rana pipiens frog skin assay.

A convenient, direct synthesis of methyl t‐butoxycarbonyl‐L‐propargylglycinate is described, and the 13C‐NMR. spectra of L‐o‐carboranylalanine recorded. The procedure was extended to the preparation of BOC · Car‐Leu · OMe from BOC · Pra‐Leu · OMe. A number of new propargylglycine derivatives are reported.
(Perhalogenmethylthio)heterocyclen. X. Säurekatalysierte Substitutionen an (Perchlorfluormethylthio)pyrrolen und deren agrobiologische Wirkung
Authors: Dorn Silvia , Eggenberg Peter , Gerstenberger Michael R. C. , Haas Alois , Niemann Ulrich , Zobrist Peter
Published: December 2004

(Perhalomethylthio)heterocycles. X

IX. Mitt.: s. [1].

.
Acid‐catalyzed substitutions on (perchlorofluoromethylthio)pyrroles and their agro‐biological activities

In the presence of C4F9SO3H the (perhalomethylthio)pyrroles 1a–c react with Cl3−nFnCSCl (n = 1–3) to give mixtures of the 2,5‐ and 2,4‐disubstituted pyrroles 2a–f and 3a–h. 2a and 3a react with CF3SCl (catalyst CF3SO3H) yielding 2,3,5‐tris (trifloromethylthio)pyrrole (4a), which under similar conditions reacts further to give 2,3,4,5‐tetrakis (trifluoromethylthio)pyrrole (5). As a by‐product during the conversion of 3a to 4a 2,3,4‐tris (trifluoromethylthio)pyrrole (4b) is formed. The pyrroles 2a, 4a and 5 form the mercury salts 6a–c; compound 5 yields also a silver salt 7. The 1H‐ and 19F‐NMR. spectra are discussed and the agro‐biological properties of the compounds investigated.
Heterocyclisch anellierte Derivate des Strychnins: Imidazo‐, Oxazolo‐ und (1,3‐Dioxolo)strychnine
Authors: Edenhofer Albrecht , Arnold Wolf
Published: December 2004

Heterocyclic anellated derivatives of strychnine: Imidazo‐, oxazolo‐ and (1,3‐dioxolo)strychnine

The synthesis of imidazo‐, oxazolo‐ and dioxolo‐strychnine derivatives, anellated at the 2,3‐position of the aromatic nucleus is described. The spectroscopic properties of these compounds and of some intermediates are given.
Conversion of Natural (S)‐Bulbocapnine into Two (Ring A)‐Substituted Derivatives of (R)‐Apomorphine
Authors: Greecke Max , Borer René , Brossi Arnold
Published: December 2004

(6aR)‐1,2‐(Methylenedioxy)aporphine‐10, 11‐diol (8) and (6aR)‐aporphine‐1, 1, 10, 11‐tetrol (16) have been prepared from natural (S)‐bulbocapnine (4). For both compounds, the partial synthesis included racemic intermediates which have been resolved into their enantiomers. Both compounds 8 and 16 showed dopaminergic activity in rats, although to a lower extent than (R)‐apomorphine (1) itself.
Etude en série triazénique. IV. Synthèse et réactivité d'aryl‐3‐(diméthyl‐3,4‐isoxazolyl‐5)‐1‐triazènes et d'arylazo‐4‐diméthyl‐3,4‐isoxazolones‐5
Authors: Siv Chhan , Vernin Gaston , Metzger Jacques
Published: December 2004

Synthesis and reactivity of 3‐aryl‐1‐(3,4‐dimethyl‐5‐isoxazolyl)‐triazenes and 4‐arylazo‐3,4‐dimethylisoxazol‐5‐ones

According to the experimental conditions and the nature of the substituents on the aromatic ring, aryldiazonium salts react with 5‐amino‐3,4‐dimethylisoxazole (3) leading to either 3‐aryl‐1 (3,4‐dimethyl‐5‐isoxazolyl)‐triazenes (1A) or 4‐arylazo‐3,4‐dimethylisoxazol‐5‐ones (4). Analyses of the products resulting from thermal decomposition of these triazenes in aromatic substrates and in DMSO and their behaviour in acidic medium show that it is essentially the arylazo form 1B which is reactive.
The Configuration of Naturally Occurring Iridoid Glucosides at C(6) and C(8): A Complementary Assignment Aid by 13C‐NMR. Spectroscopy
Authors: Chaudhuri Ratan K. , Afifi‐Yazar Fatma Ü. , Sticher Otto
Published: December 2004

Evidence is presented which demonstrates that 13C‐NMR. spectroscopy can be used with confidence in evaluating the configuration of R1R2CHOH centers at C(6) and C(8) of iridoid glucosides.
Dérivés d'énose‐ et d'ynosephosphonates et composés voisins. Communication préliminaire
Authors: Tronchet Jean M. J. , Bonenfant Alain P. , Pallie Kemal Deen , Habashi Ford
Published: December 2004

Derivatives of enose‐ and ynosephosphonates and related compounds. Preliminary communication

The gem‐dibromo terminal enoses 1 and 7 are convenient sources of glycosylacetylenes which upon reaction with phosphorus electrophiles gave the phosphorusbearing acetylenic sugars 4, 5 and 8. Compounds 5 and 8 underwent cycloaddition reactions leading to isoxazolyl‐C‐glycosides 6 and 9 respectively. The nitroolefinic sugar derivative 11 gave upon bromination‐dehydrobromination the first example of a new kind of potentially useful synthetic intermediates, the gem‐bromonitroenose 12. The enosephosphonate 13 was also prepared from 11. The diglycosylhydroxylamine 18 represents another type of phosphorus‐bearing acetylenic sugar derivative. Some 1H‐ and 13C‐NMR. data relative to the new types of phosphorus‐containing sugar derivatives synthesized are given.
Photochemische Reaktionen. 105. Mitteilung [1]. Zur Photochemie optisch aktiver λ, δ‐Epoxy‐enone: Racemisierung und Cyclisierung von (−)‐4‐Methyliden‐5,6‐epoxy‐5,6‐dihydro‐β‐jonon und (−)‐4‐Oxo‐5,6‐epoxy‐5,6‐dihydro‐β‐jonon
Authors: Frei Bruno , Wolf Hans Richard , Jeger Oskar
Published: December 2004

The photochemistry of optical active λ, δ‐epoxy‐enones. Racemization and cyclization of (−)‐4‐methylidene‐5,6‐epoxy‐5,6‐dihydro‐β‐ionone and of (−)‐4‐oxo‐5,6‐epoxy‐5,6‐dihydro‐β‐ionone

UV.‐irradiation (λ ≥ 347 nm as well as λ = 254 nm) converts the conjugated λ, δ‐epoxy‐enones (−)‐2 and (−)‐4 by cleavage of the C,C‐oxirane bond to an intermediate ketonium ylide f which cyclizes giving the racemic starting materials. The degree of racemization depends on the length of the irradiation time.

The formation of the optical active products (−)‐3 and (+)‐5 in these irradiations gives evidence, that the photocyclization of (−)‐2 und (−)‐4, respectively, is a one step reaction of a state g.
Kinetics of Ethylene Oxidation on a Supported Silver Catalyst
Authors: Dettwiler Hans Rudolf , Baiker Alfons , Richarz Werner
Published: December 2004

The kinetics of ethylene oxidation by air over a supported silver catalyst were investigated in the temperature range 490–620 K. The reaction network was found to be triangular. Under virtually constant oxygen partial pressure (0.2 bar), the following rate relationships, (in mol g−1s−1) were found: (formulae in curved brackets denote partial pressures)
equation image
where
equation image
R is expressed in J · mol−1 · K−1.

The given rate expressions are discussed in the framework of earlier kinetic investigations.
Polar Substituent Effects in the Solvolysis of Acyclic Tertiary Chlorides Polar Effects VI
Authors: Grob Cyril A. , Waldner Adrian
Published: December 2004

The influence of twenty substituents R on the solvolysis rates and products of tertiary chlorides R ‐ CH2CH2C(CH3)2Cl (7) has been studied. H, CH3, (CH3)2NCH2, ClCH2, Cl, CN and NO2 exert an inductive effect only, as the good correlation of the rates with the corresponding inductive substituent constants σ shows. Bulkier alkyl groups, i.e. isopropyl and t‐butyl, lower the rate due to a Baker‐Nathan effect, while the n‐electron donors CH3S, CH3O, HO and (CH3)2N and the σ‐electron donors (CH3)3Sn and HOCH2 cause rate increases based on σ constants. These accelerations are attributed to C,C‐hyperconjugative and inductomeric effects which arise in the transition state for ionization. A comparison of the reactivity of the acyclic chlorides 7 and the corresponding 1‐R‐substituted 3‐bromoadamantanes 1a shows that polar substituent effects are more strongly transmitted in the rigid bicyclic compounds 1a than in the flexible acyclic compounds 7.
Gilmaniellin and Dechlorogilmaniellin, Two Novel Dimeric Oxaphenalenones
Authors: Chexal Kuldip K. , Tamm Christoph , Hirotsu Ken , Clardy Jon
Published: December 2004

The structure and configuration of gilmaniellin, a metabolite of Gilmaniella humicola BARRON, has been shown to be 2 by X‐ray analysis. By comparison of spectral data structure 1 has been assigned to dechlorogilmaniellin.
Die Solvoyse von 4‐substituierten 2‐Chlor‐2‐methylbutanen
Authors: Grob Cyril A. , Waldner Adrian
Published: December 2004

The solvolysis of sixteen 4‐substituted 2‐chloro‐2‐methylbutanes in aqueous dioxane has been studied.
Halogenation of Xanthenyl and Thioxanthenylallenes
Authors: Abdul‐Malik Nadia Fouad , Awad Sami Bassili , Sakla Afly Badie
Published: December 2004

Reactions of acids with vinylidenexanthenes (or thioxanthenes) 1 and 9‐methoxy‐9‐vinylxanthenes (or thioxanthenes) 8 give xanthene‐ (or thioxanthene‐) 9‐spiro‐1′‐indenes 7. With bromine or sulfuryl chloride they give the corresponding 2′‐halogenoxanthene‐ (or thioxanthene‐)9‐spiro‐1′‐indenes 5. Formation of such derivatives depends on preferential attack of the reagents on allenes 1 to give initially xanthylium (or thioxanthylium) ions 3 which cyclize. One π bond of the allenes 1 can be selectively reduced in acid media. Chemical and spectral evidence for these routes are presented.
1,3‐Dipolar Cycloadditions to Strained Olefins
Authors: Becker Konrad B. , Hohermuth Martin K.
Published: December 2004

The Bredt olefins bicyclo [3.3.1]non‐1‐ene (2), bicyclo [4.2.1]non‐1 (8)‐ene (3), and bicyclo [4.2.1]non‐1 (2)‐ene (4) react rapidly with 1,3‐dipoles such as diazomethane, phenyl azide, and mesitonitrile oxide to yield mixtures of two regioisomeric cycloadducts 10, 11 and 12, respectively. On the contrary, cycloaddition to the comparable monocyclic 1‐methyl‐(E)‐cyclooctene (5) is fairly regioselective. 2‐Methylnorborn‐2‐ene (6) gives one isomer with mesitonitrile oxide (as do less strained olefins), but mixtures with diazomethane and phenyl azide. 1H‐NMR. and 13C‐NMR. spectra of the cycloadducts are reported. The results are discussed in the light of frontier molecular orbital theory.
Isomerisierung der Bis(triphenylphosphin)platin(0)‐Komplexe von Bicyclo[4.2.1]non‐1‐en und Bicyclo[4.2.1]non‐1(8)‐en
Authors: Stamm Erich , Becker Konrad B. , Engel Peter , Keese Reinhart
Published: December 2004

Isomerization of the Bis(triphenylphosphine)platin(0) Complexes of Bicyclo[4.2.1]non‐1‐ene and Bicyclo[4.2.1]non‐1(8)‐ene

Isomrisation of the Bredt‐Olefins 3 and 7 as the bis (triphenylphosphine)‐Pt(0) complexes 1 and 8, respectively, has been observed. The bridgehead‐olefin 3 as well as the bicyclic olefins 4, 5 and 6 have also been isomerized with catalytical amounts of (ethylene)bis(triphenylphosphine)platinum(0) (2).
Etude par spectrométrie de masse d'une série d'alcanediphtalimides‐α,ω
Authors: Blanc Pierre‐Alain , Gülaçar Fazil O. , Buchs Armand
Published: December 2004

Mass spectrometric study of a series of alkane‐α,ω‐diphthalimides

Alkane‐α,ω‐diphthalimides with three to seven aliphatic C‐atoms were synthesized and their mass spectral behaviour investigated in detail with the aid of the deuteriated derivatives of hexane‐1,6‐diphthalimide. Besides the expected hydrogen rearrangements, an interesting skeletal rearrangement has been observed.
A Total Synthesis of α‐Kainic Acid by an Intramolecular Ene Reaction. Preliminary communication
Authors: Oppolzer Wolfgang , Andres Hendrik
Published: December 2004

The neurotoxin α‐kainic acid (7) was synthesized from 1 via the thermal key step 5 → 6 in 41% overall yield.
Chirale 2,2′‐Polyoxaalkano‐9,9′‐spirobifluorene
Authors: Prelog Vladimir , Bedeković Davor
Published: December 2004

Chiral 2,2′‐polyoxaalkano‐9,9′‐spirobifluorenes

From 2,2′‐diacetyl‐9,9′‐spirobifluorene (2), twelve chiral polyethers have been prepared as potential ion‐ and enantiomer‐selective ionophores. The absolute configuration of the polyethers 15–17, 19–22, and 25 has been determined by chemical correlation with vespirenes [11] [29], by circular dichroism, and by X‐ray analysis. The circular dichroism of 15–17, 19 and 21 depends on the size of the macrocycle and indicates that the fluorene chromophores of 19 and 21 with 13‐ and 16‐membered rings respectively deviate considerably from orthogonality.
Elektrochemische Untersuchungen über das enantiomerenselektive Verhalten von chiralen Ionophoren in flüssigen Membranen
Authors: Thoma André P. , Viviani‐Nauer Angelika , Schellenberg Kurt H. , Bedeković Davor , Pretsch Ernö , Prelog Vladimir , Simon Wilhelm
Published: December 2004

Electrochemical Investigations of the Enantiomer Selectivity of Chiral Ionophores in Liquid Membranes

The enantiomer selectivity of a series of chiral neutral ionophores was investigated by electrochemical methods using ionophore‐solvent‐polymer membranes and chiral ammonium salts as substrates. The potentiometrically determined enantiomer selectivities are in good agreement with the results of electrodialytic transport studies.
Carbocyclen aus Monosacchariden. III. Zur Diastereoselektivität der Bildung von Cyclopentanderivaten. Umsetzungen in der Galactosereihe
Authors: Bernet Bruno , Vasella Andrea
Published: December 2004

Carbocycles from monosaccharides. III. Concerning the diastereoselective formation of cyclopentane derivatives. Transformations in the galactose series.

The diastereoselectivity of the intramolecular nitrone‐olefine cycloaddition of 1, 3 and 4 (Scheme 1), yielding only 2, 5 and 6 but none of the isomers 8, 9 and 10 is explained by assuming a kinetic control and postulating that the relative activation energies of the two relevant transition states in the cyclization of e.g. 1 can be estimated from the conformers A and B, the latter being destabilized by a synperiplanar arrangement of the nitrone function and the 2‐alkoxy‐group (Scheme 2). It is further postulated, that this destabilization is responsible for the formation of (2,3)‐trans configurated products. Since 2, 5 and 6 are presumably thermodynamically more stable than 8, 9 and 10, a case was investigated, where the cycloaddition can either give thermodynamically less stable (2,3)‐trans‐product such as 12 or a thermodynamically more stable (2,3)‐cis‐product such as 13. 12 and 13 could both be formed from the aldehyde 25 via the nitrone 11 (Schemes 3 and 5). Treatment of the galactoside 16 first with Zn in aqueous butanol (forming among other products 25 and its 2‐debenzyl‐oxy‐derivative) and then with N‐Methyldroxylamine yielded the isoxazolidines 12 (72%), 13 (2%) and 27 (7%) (Schemes 4 and 6). Similarily, the anomeric silylated galactosides 17 and 23 gave 29 (78% from 17, 77% from 23) and 27 (5% and 3%). Upon desilylation, 29 gave 32, which was converted into 12. The structure of the isoxazolidines was unambiguously deduced from their NMR. spectra and those of their derivatives 33 and 34. Compound 32 was further transformed into its deoxyderivative 36. The high diastereoselectivity of the cycloaddition restricts the number of diastereomeric, pentasubstituted cyclopentanes available by this method. However, cyclization of the 2‐Hydroxy‐aldehyde 37 (Scheme 8) gave the kinetically less favoured isomer 40 in a higher proportion, showing the differential influence of hydrogen‐bonds on the relevant activation energies. Thermolysis of 32 gave 40 (79%) and 41 (11%). The structure of 41 was deduced from its NMR. spectra and those of its derivatives 42 and 43. Thermolysis of 29 gave, after desilylation, 41 (42%), 40 (22%) and 32 (13%) and thermolysis of 6 lead to a 25 : 75 equilibrium with 44 (combined yield 90%). These transformations illustrate means leading to additional isomers and are in agreement with the proposed explanation of the diastereoselectivity in question.
Towards the Construction of a Complete Cyclic Water Decomposition System, Design and Operation of an Oxygen Producing Half Cell
Authors: Kalyanasundaram Kuppuswamy , Mićić Olga , Pramauro Edmondo , Grätzel Michael
Published: December 2004

Oxygen is generated when aqueous solution of iron (III) tris(2,2′‐bipyridyl), Fe(bipy), are brought in contact with catalytic amounts of powdered or colloidal RuO2. The oxygen yield depends strongly on the pH, reaching a maximum between pH 7 and 8 where it corresponds to the stoichiometry of the reaction:
equation image

The rate of the reaction is so fast that it occurs practically upon dissolution of Fe(bipy) in the aqueous phase. In acidic media (pH 4), no O2 evolution is observed. Instead, Fe(bipy) is converted to an intermediate which in the presence of RuO2 yields O2 upon neutralization.

The pH profile of the O2 evolution occuring upon illumination of Ru(bipy) in the presence of the cobalt complex [Co(NH3)5Cl]2+ was also investigated.

The surprisingly low energy losses (160 mV) in reaction (1) makes the construction of four quanta water splitting systems feasible.
High Pressure 17O‐FT‐NMR. Evidence for the Associative Nature of Substitution Reactions on Mn2+ in Water
Authors: Ducommun Yves , Newman Kenneth E. , Merbach André E.
Published: December 2004

The water exchange on [Mn(H2O)6](ClO4)2 in aqueous solution has been studied as a function of pressure (up to 250 MPa), measuring 17O‐FT‐NMR. linewidths of the free water resonance at 8.13 MHz. A pressure independent volume of activation, ΔV≠ = −6.2 ± 0.2 cm3 mol−1 is obtained, producing a clear evidence that, contrary to general belief, the mechanism for solvent exchange on Mn2+ is an associative interchange (Ia).
Sorellin und Hobartin, zwei neue Indolalkaloide aus Aristotelia peduncularis (LABILL.) HOOK. F. 173. Mitteilung über organische Naturstoffe
Authors: Kyburz Rolf , Schöpp Emanuel , Hesse Manfred , Bick I. Ralph C.
Published: December 2004

Sorelline and Hobartine, Two New Indole Alkaloids from Aristotelia peduncularis (LABILL.) HOOK. F.

From Aristotelia peduncularis (LABILL.) HOOK. F. two new indole alkaloids, sorelline (1) and hobartine (2), have been isolated. Their structures were elucidated on the basis of spectroscopic data (the formulae represent their relative configurations). The alkaloids 1 and 2 have closely related structures with a monosubstituted indole moiety and an unrearranged monoterpene unit in the aliphatic part.
Metal Complexes with Macrocyclic Ligands. XIV. Formation, dissociation and metal exchange with an N2S2‐macrocycle
Authors: Kallianou Chariklia S. , Kaden Thomas A.
Published: December 2004

10, 10, 12‐Trimethyl‐3,4‐benzo‐1,6‐dithia‐9,13‐diazacyclopentadecen‐dihydrochloride (LH, 2) and its Ni2+ complex were synthesized and their reactivity studied. The formation kinetics of 2 with Cu2+ were found to be a second order reaction between Cu2+ or CuACO+ and the monoprotonated form of the ligand LH+. The rate constant k = 29 M−1S−1 is 105–106 times smaller than those of monoprotonated tetraazamacrocycles either because of second bond formation or because of a strong electrostatic interaction between the positive charges of the Cu2+ and the ammonium group. The metal‐metal exchange between NiL+ and Cu2+ was also investigated. The reaction is independent of [Cu2+] and has the same rate and activation parameters as the dissociation of NiL2+. In contrast to open chain ligands, no mixed complex CuNiL4+ as intermediate was observed.
Über Pterinchemie. 72. Mitteilung. Trennung der Diastereomeren (6R)‐ und (6S)‐5,6,7,8‐Tetrahydro‐L‐biopterin
Authors: Furrer Hans‐Jürg , Bieri Jost H. , Viscontini Max
Published: December 2004

Separation of the Diastereomers (6R)‐ and (6S)‐5,6,7,8‐Tetrahydro‐L‐biopterin

The mixture of the diastereomers of the tetraacetylderivative IV of (6RS)‐5,6,7,8‐tetrahydro‐L‐biopterin could be separated by fractional crystallisation in methanol into the diastereomers IV A and IV B. Hydrolysis with hydrochloric acid gives the pure, diastereomeric, (6R)‐ and (6S)‐5,6,7,8‐tetrahydro‐L‐biopterins.
2‐Oxocephems. Synthesis and Properties of 7‐Acylamino‐2‐oxocephem‐4‐carboxylic Acids
Authors: Ernest Ivan
Published: December 2004

A synthesis of (6 R, 7 R)‐7‐acylamino‐2‐oxocephem‐4‐carboxylic acids from penicillins is reported based on the formation of the 2‐oxocephem system in an intramolecular Wittig condensation. An interesting steric effect of the acylamino grouping on the course of this key step was used to advantage. Some physical and biological properties of this new type of Δ3‐cephem are described.
Iridoidglucoside aus Leucocarpus perfoliatus G. DON. 174. Mitteilung über organische Naturstoffe
Authors: Ozaki Yutaka , Hesse Manfred , Johne Siegfried
Published: December 2004

Iridoidglucosides from Leucocarpus perfoliatus G. DON.

The known iridoid glucoside boschnalosid (1) was isolated from Leucocarpus perfoliatus in addition to the hitherto unknown yuheinosid, for which structure 2 was deduced.
The Course of the Catalytic Hydrogenation/Isomerization Reaction of Steroidal Ring B Olefins in the 13β‐ and 13α‐Series
Authors: Acklin Georg , Graf Walter
Published: December 2004

The course of the catalytic hydrogenation and isomerization (H2/Raney‐Ni/dioxane or H2/Pd/C/EtOH) of Δ5.7‐, Δ7‐, Δ8‐, and Δ8(14)‐steroid olefins was shown to depend strongly on the configuration at C(13). The known hydrogenation/isomerization of reactions of Δ5.7‐dienes in the 13β‐series to Δ7‐(H2/Raney‐Ni/dioxane) and Δ8(14)‐olefins (H2/Pd/C/EtOH) were also confirmed in the 3β, 19‐epoxy‐13β‐ and 3‐Oxo‐19‐acetoxy‐13β‐steroid series (e.g. 32 → 35 → 37, Scheme 3). On the other hand, in the corresponding 13α‐steroid series the same reactions afforded the Δ7‐. and the Δ8‐olefins (mixture of products with H2/Raney‐Ni/dioxane; quantitatively the Δ8‐compounds with H2/Pd/C/EtOH; s. e.g. Scheme 3). A similar dependence on the C(13) configuration was observed in the allylic oxidation of these olefins with SeO2 (Fieser's test, see Table), and in the acid catalyzed opening of the 7α, 8α‐epoxides (e.g. 60 → 62 + 63 in the 13β‐series, and 56 → 64 + 65 in the 13α‐series, Scheme 8).
The photoelectron spectra of D2d and C2ν hydrocarbons containing two norbornadiene or quadricylane groups
Authors: Kovač Branka , Heilbronner Edgar , Prinzbach Horst , Weidmann Klaus
Published: December 2004

The photoelectron spectra of the hydrocarbons 1 to 4 have been recorded and interpreted by qualitative correlation with the spectra of their subsystems norbornadiene, quadricyclane, allene and cyclopropane.

It has been shown that the interactions of the symmetry adapted orbitals of the subsystems are governed not only by their symmetry behaviour with respect to D2d in 1 and 2, or C2ν in 3 and 4, but also by the local symmetry at the points of attachment of the subsystems.
Synthese von (‐)‐(R)‐4‐Hydroxy‐β‐ionon und (‐)‐(5 R, 6 S)‐5‐Hydroxy‐4,5‐dihydro‐α‐ionon aus (‐)‐(S)‐α‐Ionon
Authors: Haag Andreas , Eschenmoser Walter , Eugster Conrad Hans
Published: December 2004

Synthesis of (‐)‐(R)‐4‐Hydroxy‐β‐ionone and (‐)‐(5 R, 6 S)‐5‐Hydroxy‐4,5‐dihydro‐α‐ionone aus (‐)‐(S)‐α‐Ionone

The absolute configuration of the chiral 4‐hydroxy‐β‐ionones and 5‐hydroxy‐4,5‐dihydro‐α‐ionones has been determined by chemical connection with (‐)‐(S)‐α‐ionone i.e. by stereoselective epoxidation of the latter, followed by base catalyzed opening of the epoxide as well as by its hydride reduction.
A Reexamination of Inductive Substituent Constants Derived from pKa Values of 4‐Substituted Quinuclidines. Polar effects. Part VIII
Authors: Grob Cyril A. , Schaub Bruno , Schlageter Markus G.
Published: December 2004

pKa Values of 42 quinuclidinium perchlorates I have been measured in 0.1 M aqueous KCl‐solution. In a few cases small corrections of earlier thermodynamic pKa values are indicated. These measurements, in conjunction with recent X‐ray structure determinations, confirm the reliability of the inductive substituent constants σIq derived from them.
Approaches to the Synthesis of Cytochalasans. Part 2. Pyrrolinone derivatives as basic units
Authors: Schmidlin Tibur , Tamm Christoph
Published: December 2004

Several attempts to prepare 3‐acetyl‐5‐benzyl‐3‐pyrrolin‐2‐one (7) from phenylalanine are described. This goal was only reached formally, because compound 7 exists in the tautomeric form of (Z)‐5‐benzyl‐3‐(1′‐hydroxyethylidene)‐4‐pyrrolin‐2‐one (17) according to the spectral data. The problem of tautomerism in pyrrolinone systems is discussed.
Valence Delocalization in Prussian Blue Fe[FeII(CN)6]3 · XD2O, by Polarized Neutron Diffraction
Authors: Day Peter , Herren Fritz , Ludi Andreas , Güdel Hans Ulrich , Hulliger Fritz , Givord Dominique
Published: December 2004

Polarized neutron diffraction has been used to investigate the spin delocalization from the high‐spin Fe(III) sites to the low‐spin Fe(II) in deuteriated Prussian Blue, Fe4[Fe(CN)6]3 · xD2O. Measurements of the 111, 200, and 400 reflections were made on a powdered sample at 3 K and 4.8 T using a neutron wavelength of 1.074 Å. The expectation value of S at the Fe(II) site is ‐ 0.008 ± 0.028 corresponding to an upper limit of about 5% of an electron for the spin delocalization.
Photochemische Reaktionen. 106. Mitteilung. Zur Photochemie tetraalkylsubstituierter γ‐Keto‐olefine
Authors: Berger Jacob , Yoshioka Michikazu , Zink Markus P. , Wolf Hans R. , Jeger Oskar
Published: December 2004

The Photochemistry of Tetraalkyl Substituted γ‐Keto‐olefines

The photochemistry of 7,8‐dihydro‐β‐ionone (1) in solution is shown to depend on temperature, polarity and viscosity of the solvent. UV. irradiation (λ ≥ 245 nm) in pentane at +25° converts 1 to the isomeric ethers 3 (16%), 5A (48%) and 5B (22%), whereas at −65° 7,8‐dihydro‐γ‐ionone (26) is obtained in 12% yield together with 13% of 3, 12% of 5A and 9% of 5B. The 1n,π*‐excitation of 1 in acetonitrile gives similar results. In the more viscous 1,2,3‐triacetoxypropane the photoisomerization 1 → 26 takes place even at + 60° (10% yield, cf. 40% at −15°). In alcoholic solvents, however, no formation of 26 is detected, but the hitherto unknown [2+2]‐photocycloaddition 1 → 11 can be observed (4% at −7°, 15% at −65S° in 2‐propanol). An intermediate e may be involved (Scheme 14). In addition to the photoreactions 1 → 3, 5A, 5B and 11 the isomerization of 1 to the novel spirocyclic ketone 28 takes place in alcoholic solvents only.

Photoisomerization 1 → 3 is presumably a photo‐ene process involving a stereoselective intramolecular H‐transfer. This type of photoisomerization is restricted to cyclic γ‐keto‐olefines. The tetraalkylated acyclic γ‐keto‐olefines 14 and 15 photoisomerize exclusively by [2+2]‐cycloaddition, independent of the solvent.

On 1n,π*‐excitation the δ,ϵ‐unsaturated bicyclic ketone 44 undergoes Norrish‐Type‐II photofragmentation to the diene 45 or isomerizes to the γ, ϵ‐unsaturated ketone 17. Competition between these two reactions is strongly temperature dependent: photolysis in pentane at −72° yields quantitatively 45, whereas at + 35° only 30% of 45 and 68% of 17 are obtained.

UV. irradiation of the novel spirocyclic ketone 28 gives as primary photoproduct the isomeric aldehyde 29, and in a secondary photoreaction the isomeric oxetanes 30A and 30B. Experiments with deuteriated substrates show that the isomerization of type 28 → 29 is stereocontrolled.
Revision of the Structure of ‘Epoxycolchicine’
Authors: Brossi Arnold , Rösner Manfred , Silverton James V. , Iorio Maria A. , Hufford Charles D.
Published: December 2004

Revision der Struktur von «Epoxycolchicin»

Die für natürliches «Epoxycolchicin» vorgeschlagene Struktur 2 muss aufgrund einer Kristall‐Röntgenstrukturanalyse zu derjenigen des cyclischen Acetals 3 abgeändert werden. Es wird vorgeschlagen, den Namen «Epoxycolchicin» aus der Literatur zu streichen, da er irreführend ist.
Light Induced Redox Reactions of Water Soluble Porphyrins, sensitization of hydrogen generation from water by zincporphyrin derivatives
Authors: Kalyanasundaram Kuppuswamy , Grätzel Michael
Published: December 2004

The photoredox behaviour of two water soluble derivatives of zincporphyrin, 5,10,15,20‐tetra‐p‐sulfonatophenyl (1) and 5,10,15,20‐tetra‐p‐N‐methylpyridiniochloride (2), was investigated using laser and continuous photolysis techniques. Photoexcitation produces triplet states whose lifetimes in aqueous solution exceeds 1 ms. These triplet states can be quenched reductively by donors such as EDTA and oxidatively by acceptors such as methylviologen (MV2+). Electron transfer to MV2+ is greatly influenced by the charge of the porphyrin, rate constants being 1.4 x 1010M−1S−1 and 2 × 106M−1S−1 for 1 and 2, respectively. In the presence of colloidal Pt catalyst, the cationic porphyrin sensitizes photoreduction of water to hydrogen with remarkable efficiency.
Oxygen‐17 and Carbon‐13 Nuclear Magnetic Resonance. Chemical shifts of unsaturated carbonyl compounds and acyl derivatives
Authors: Delseth Claude , Nguyên Thi Thanh‐tâm , Kintzinger Jean‐Pierre
Published: December 2004

The 17O and 13C chemical shifts (δ) of 14 α,β‐unsaturated aldehydes and ketones and 33 acyl derivatives RXC = O (X = Cl, OH, OMe, OEt, NH2 and R = H or alkyl) have been measured. In the unsaturated carbonyl series, a correlation exists between δ 17O and the π electron density at the β‐carbon atom. From this correlation, an δ 17O of 530 ppm was extrapolated for the loss of one electron at the oxygen atom. In the acyl series, the δr 17O were also sensitive to changes in the polarity of the carbon‐oxygen bond. A partial correlation between 17O‐NMR. chemical shifts and the nuclear quadrupole coupling constants exists for aldehydes, ketones, esters and amides but not for acyl chlorides.
Preparation and Electrophilic Substitution of 1‐Trimethylsilylpentadienyllithium
Authors: Oppolzer Wolfgang , Burford Sidney C. , Marazza Fabrizio
Published: December 2004

Pentadienyllithium (16) was regioselectively and efficiently transformed to 1‐trimethylsilyl‐2,4‐pentadiene (17) by reaction with chlorotrimethylsilane (Scheme 5). Deprotonation of 17 and subsequent electrophilic attack furnished the regioisomeric products 12 and/or 13 in good yields (Schemes 5 and 6). The utility of the reaction 18→12 for the convergent assembly of the 1‐silyl‐1,3‐butadiene unit with an olefinic dienophile is further illustrated by the smooth intramolecular Diels‐Alder reaction 19→20.
Nachweis von Fragment‐Genesen im Massenspektrometer. 5. Mitteilung Aminosäure‐Sequenzanalyse: Vergleich der DADI/MIKE‐, ‘linked scan’‐ und Kollisionsaktivierungs‐Spektrometrie an aliphatischen Aminosäuren
Authors: Steinauer René , Walther Hansjörg , Schlunegger Urs Peter
Published: December 2004

Detection of Fragment Genesis in the Mass Spectrometer. V. Amino Acid Sequence Analysis by DADI/MIKE, Linked Scan and Collisional Activation Mass Spectrometry. Aliphatic Amino Acids

The amino acid sequence in tripeptides and tetrapeptides has been analyzed by DADI/MIKE and B/E‐‘linked scan’ spectrometry, as well as by collisional activation in the first and second field free region of a mass spectrometer embodying the inverse Nier‐Johnson geometry. Collisional activation enhances the intensity of fragment ions.
Substituierte Alkylsulfonate durch Addition von Natriumhydrogensulfit an Chalkone
Authors: Pfoertner Karl‐Heinz
Published: December 2004

Substituted Alkyl Sulfonates by Addition of Sodium Hydrogen Sulfite to Chalcones

Sodium hydrogen sulfite adds to the C, C double bond of chalcones to give substituted alkyl sulfonates 1. Reaction of methyl iodide with the pyridyl substituted alkyl sulfonates 1b–1e yields the inner salts 2–4.
Etude de la fragmentation par impact électronique de dérivés du benzothiazole
Authors: Claude Saturnin , Tabacchi Raffaele , Due Laurent , Fuchs Rudolf , Boosen Karl‐Josef
Published: December 2004

Study of Electron‐Impact Fragmentation of Benzothiazole Derivatives

The mass spectra of eighteen substituted benzothiazoles are reported and discussed. All these compounds are thermodynamically stable and give an intense molecular ion, which undergoes different types of fragmentation depending on the nature of the substituent which is rarely eliminated directly. β‐Cleavage with respect to the heterocyclic double bond is often observed. Specific 2H‐, 13C‐, 15N‐ and 34S‐labelling have been used in order to confirm the fragmentation patterns.
Synthesis, Properties, and Crystal Structure of Silyl Nitronates (Silyl Esters of aci‐Nitroalkanes): Towards the SN2 Reaction Path with Retention of Configuration at Silicon
Authors: Colvin Ernest W. , Beck Albert K. , Bastani Bahram , Seebach Dieter , Kai Yasushi , Dunitz Jack D.
Published: December 2004

An efficient and flexible method for the preparation of silyl nitronates is described (see 1–10). NMR. spectral investigations indicate a rapid 1,3‐silyl migration process, with an activation energy of about 10 kcal mol−1. X‐ray crystallographic studies on the silyl nitronates 3 and 8 show structures that lean towards an SN2 retention pathway at silicon.
Natural Occurrence of Enantiomeric and meso‐Astaxanthin 1. Ex Lobster Eggs (Homarus gammarus)
Authors: Rønneberg Harald , Renstrøm Britta , Aareskjold Kåre , Liaaen‐Jensen Synnøve , Vecchi Max , Leuenberger Franz J. , Müller Robert K. , Mayer Hans
Published: December 2004

Astaxanthin (1; 3,3′‐dihydroxy‐β,β‐carotene‐4,4′‐dione) isolated from lobster eggs (Homarus gammarus) was unexpectedly found to be a mixture of all three optical isomers as determined by HPLC. analysis of the corresponding diesters of (–)‐camphanic acid. This is the first finding of meso‐astaxanthin and a meso‐carotenoid in general in nature.
Intramolekularer Carbonylgruppenaustausch in Tetracarbonyleisen‐Komplexen von Äthylen und einfachen (E)‐konfigurierten Olefinen
Authors: Von Büren Martin , Cosandey Marcel , Hansen Hans‐Jürgen
Published: December 2004

Intramolecular Exchange of Carbonyl Group Sites in Tetracarbonyliron Complexes of Ethylene and Simple (E)‐Configurated Olefins

The activation parameters of the intramolecular exchange of carbonyl group sites in the tetracarbonyliron complexes 2–5 of ethylene, (E)‐2‐butene, (E)‐4‐octene and (E)‐cyclooctene, respectively have been determined between 180 and 115 K by a complete line shape analysis of the 13C‐NMR, signals of the CO‐groups. The temperature dependence of the rates (k (2), k (3), k (4) and k (5), respectively) of this intramolecular exchange process can be described by the following equations (Ea in J/mol):

Further data are given in Tables 3 and 4.

Furthermore, a good linear correlation between the energies of activation of the carbonyl exchange process in 1,2‐disubstituted olefins and the corresponding averaged wavenumbers ( (CO)) of the carbonyl stretching vibrations or of the corresponding chemical 13C‐shifts (δ (CO)) of the carbonyl group at fast exchange in the complexes seems to exist.
Biosynthesis of the antibiotic verrucarin E use of [1‐13C]‐, [2‐13C]‐, [1,2‐13C]‐ and [2‐13C, 2‐2H3]‐acetates. Verrucarins and roridins, 37th communication [1]
Authors: Chexal Kuldip K. , Snipes Carl , Tamm Christoph
Published: December 2004

The origin of the carbon skeleton of verrucarin E (1) from acetate as precursor is confirmed. Incorporation studies with [1,2‐13C]‐acetate have demonstrated that two acetoacetate units couple together as shown in pattern A (Scheme 2) and not as in B. Analysis of the deuterium distribution in both verrucarin E (1) isolated after the incorporation of [2‐13C,2‐2H3]‐acetate and in sodium acetate obtained after Kuhn‐Roth oxidation of the metabolite demonstrated that C(7) is derived from the starter unit of one of the acetoacetate moieties. The deuterium exchange in verrucarin E (1) occurring during fermentation was investigated.
On the Basicity of Triarylmethylamines in Solution
Authors: Dahn Hans , Farine Jean‐Claude , Nguyên Thi Thanh Tâm
Published: December 2004

The pK of 11 triarylmethylamines (tritylamines), eight of which are new, and some related bases were measured in methylcellosolve/water 80:20 (MCS); some were also measured in dioxane/water 60:40 (Dx), acetonitrile (An), nitrobenzene (Nb) and acetic acid (Ac). (1) The influence of the aryl groups on the basicity is essentially additive; (2) In different solvents, similar linear free energy relationships were found, with differences in p* characteristic of solvation; (3) The influence on basicity of substituents of the aryl groups follows Hammett's relationship. These results indicate a preponderance of inductive effects. N, N‐Dimethyltritylamine (3b) (pK=3.40) shows a marked crowding effect, absent in the isomeric tertiary amines 13 and 14. Tri‐p‐nitrotritylamine (10a) (pK=3.10), N, N‐dimethyl‐tri‐p‐nitrotritylamine (10b) (pK=0.50), and 3b are particularly weak bases; the base‐weakening effect of the trinitrotrityl group is similar to that of the cyanomethyl and trifluoroethyl groups.
The Synthesis of 3,5‐Diamino‐1,2,4‐oxadiazoles. 2nd Communication
Authors: Tilley Jefferson W. , Ramuz Henri , Levitan Paul , Blount John F.
Published: December 2004

The 5‐amino‐3‐arylamino‐1,2,4‐oxadiazoles 2 are conveniently prepared by oxidative cyclization of the arylamidinoureas 10. The process is also capable of producing a variety of the 5‐substituted‐amino analogs 32 when the appropriately substituted guanidine 31 is employed as the substrate. Two different types of rearrangement leading to triazol‐3‐ones accompany cyclization depending on the choice of starting material. The structures of the rearranged products were established by X‐ray crystallographic analysis and the reaction mechanisms leading to these unexpected products are discussed.
The Photoelectron Spectra of Ni, Pd, Pt‐Diallyl
Authors: Böhm Michael C. , Gleiter Rolf , Batich Christopher D.
Published: December 2004

The He (I) photoelectron (PE.) spectra of bis (π‐allyl)palladium (2a), bis (π‐allyl)platinum (3a), bis (π‐methallyl)palladium (2b) and bis (π‐methallyl)‐platinum (3b) have been recorded and compared with the PE. spectra of bis (π‐allyl)nickel (1a) and bis (π‐methallyl)nickel (1b). By use of the He (II) PE. spectra 2a, 2b and 3b and correlations between the PE. spectra of 1–3 it is possible to assign the first seven to eight transitions in the PE. spectra of 1–3. In contrast to previous assignments it is shown that the first band in the PE. spectrum of 1a corresponds to the ejection of an electron from 7au, a pure ligand orbital. The assignment proposed is supported by semiempirical calculations of the INDO‐type by considering the relaxation effects explicitly using the ΔSCF and transition operator method.
Der Einbau von Magnesium in Liganden der Chlorophyll‐Reihe mit (2,6‐Di‐t‐butyl‐4‐methylphenoxy)magnesiumjodid
Authors: Zass Engelbert , Isenring Hans Peter , Etter Rolf , Eschenmoser Albert
Published: December 2004

Introduction of Magnesium into Ligands of the Chlorophyll Series by (2,6‐Di‐t‐butyl‐4‐methylphenoxy)magnesium Iodide

Experimental details are given for the new method of introducing magnesium into porphinoid ligands by (2,6‐di‐t‐butyl‐4‐methylphenoxy)magnesium iodide (1), previously published in preliminary form [1]. Besides magnesium octaethylporphyrinate (14), methyl pyrochlorophyllide a (10), methyl chlorophyllide a (8), and methyl bacteriochlorophyllide a (12), the complexation of pheophytin a (2) to chlorophyll a (3) and of pheophytin b (4) to chlorophyll b (5) are described.
Photochemistry of Biliverdin IX δ as a model for the study of the photoproducts from natural biliverdin IXγ (pterobilin)
Authors: Bois‐Choussy Michèle , Barbier Michel
Published: December 2004

The configurations of biliverdin‐IXγ and ‐IXδ dimethyl esters 1 and 2 in solutions, have been studied using Nuclear‐Overhauser‐Effect (NOE) experiments. Irradiation (500‐700 nm) of biliverdin IXδ gave syn‐Z → anti‐E isomerization of the central methine bridge and in aerated polar solutions, four new cyclized pigments were isolated for which structures 3, 4, 5 and 6 are proposed. Neobiliverdin IXδ 3 is also formed in degassed solution (Φ=4.10−5) but pigments 4, 5 and 6 arise from photo‐oxidation with O2. Biliverdin IXδ appears to be a good model for the study of photo‐reactions occurring on the vinyl groups of the natural biliverdin IXγ (pterobilin).