bluuebunny/crossref_metadata_2025 huggingface dataset:
Biosynthesis of Benzo[c]phenanthridine Alkaloids Sanguinarine, Chelirubine and Macarpine
Authors: Takao Narao , Kamigauchi Miyoko , Okada Momoyo
Published: December 2004

The biosynthesis of the benzo[c]phenanthridine alkaloids was investigated in a cell suspension culture of Macleaya cordata (papaveraceae). Feeding experiments define the biosynthetic pathway (–)‐7,8,13,13a‐tetrahydrocoptisine →(–)‐cis‐N‐methyl‐7,8,13,13a‐tetrahydrocoptisinium salt 15→ protopine (5)→ sanguinarine (1)→ chelirubine (3)→ macarpine (4).
Deblocking ofo‐Nitrophenylsulfenyl‐Protected Peptides by Ammonium Thiocyanate and (2‐Methyl‐1‐indolyl)acetic acid
Authors: Lüscher Immanuel F. , Schneider Conrad H.
Published: December 2004

The thiocyanate cleavage of theNa‐o‐nitrophenylsulfenyl group from peptides in solution or on a solid support proceeds effectively in the presence of (2‐methyl‐1‐indolyl)acetic acid. This scavenger was prepared from 2‐methylindole and sodium bromoacetate; it can readily be removed by extraction with base after the cleavage reaction, together with (2‐methyl‐3‐(2‐nitrophenylthio)‐1‐indolyl)acetic acid.
Propellanes. LXVI. Exo‐ and Endo‐Diels‐Alder adducts of 4‐substituted 1,2,4‐triazoline‐3, 5‐diones with various 1, 6‐methano [10]annulenes
Authors: Ashkenazi Pnina , Kaftory Menachem , Ginsburg David
Published: December 2004

Relatively few exo‐adducts have been obtained from the title compounds. Only one such mono‐adduct, 3, is known. Several exo‐endo‐bis‐adducts have been obtained but the structure of one of these, 5, has been proved unequivocally by X‐ray structural determination.
Electronic States of Phenylene and Naphthylene Bicyclobutanes. Linear Dichroism in Stretched Polyethylene
Authors: Spanget‐Larsen Jens , Gubernator Klaus , Gleiter Rolf , Thulstrup Erik W. , Bianco Bernard , Gandillon Gérard , Burger Ulrich
Published: December 2004

Excited singlet states of bicyclobutylene‐benzene (2), 1,2:4,5‐bis (bicyclo‐butylene)benzene (3), 2,3‐bicyclobutylene‐naphthalene (4), and 1,8‐bicyclobutylene‐naphthalene (5) are investigated by means of linear dichroic absorption spectroscopy of molecules oriented in stretched polyethylene films and by semiempirical model calculations. The results indicate a strong hyperconjugative impact of the bicyclobutylene group on the aromatic chromophores in these compounds. Valence isomerization to aromatic products is predicted as the preferred photochemical pathway.
Syntheses of Optically Active Verrucarinic Acid. 40th Communication on Verrucarins and Roridins
Authors: Herold Peter , Mohr Peter , Tamm Christoph
Published: December 2004

Three syntheses of (2S, 3R)‐2,5‐dihydroxy‐3‐methylpentanoic acid (verrucarinic acid) and its derivatives suitably protected for the further transformation to macrocyclic trichothecenes are described. These involve an enantioselective ester hydrolysis by pig liver esterase, a Sharpless epoxidation and an asymmetric hydroboration.
Tricyclo[3.3.0.02,8]Octanones as Building Blocks in Natural Products Synthesis. II. A new synthesis of loganin
Authors: Kon Kenji , Isoe Sachihiko
Published: December 2004

The stereocontrolled synthesis of loganin from 4‐methyltricyclo[3.3.0.02,8]octan‐3‐one is described.
The Synthesis of n,n‐Dimethyl‐2‐(1‐phenyl‐2,5‐cyclohexadien‐1‐yl)‐ethylamine and of Mesembrine‐Like Metabolites of this Potential Analgesic
Authors: Müller Peter M. , Pfister Rudolf
Published: December 2004

The synthesis of the analgesic compound N,N‐dimethyl‐2‐(1‐phenyl‐2,5‐cyclohexadien‐1‐yl)ethylamine (1) is described. Its structural relation to morphine and its pharmacological activity is shortly discussed. The isolation of three mesembrinelike metabolites of 1 from the plasma of rats is reported along with synthetic work permitting the determination of the relative configuration of these metabolites.
Photosensitized Oxygenation of Abieta‐7,9(11)‐dien‐13β‐ol
Authors: Zelnik Raymond , Rabenhorst Ema , Haider Akhtar , Lauterwein Jürgen , Wyler Hugo
Published: December 2004

Dehydration of abiet‐8‐ene‐7β, 13β‐diol (ibozol, 1) leads to abieta‐7,9(11)‐dien‐13β‐ol (2) which aromatizes slowly to the known abieta‐8,11,13‐triene (3). Photosensitized oxygenation of the heteroannular diene 2 yields a mixture from which three compounds were identified; abiet‐7‐ene‐9α, 11α, 13β‐triol (4), abieta‐8,11,13‐trien‐7‐one (5), and abieta‐8,11,13‐trien‐7α‐ol (6).
Temperature Dependence of the Isobutane Chemical Ionization Mass Spectra of Open‐chain and Cyclic Alcohols; Structural, Stereochemical and Molecular‐Size Effects. A reevaluation of the isobutane chemical ionization of alcohols
Authors: Winkler Fritz Johann , Gülaçar Fazil O. , Mermoud François , Buchs Armand
Published: December 2004

The temperature dependence of the isobutane chemical ionization (CI.) mass spectra of 54 open‐chain, cyclic and unsaturated C5‐ to C10‐alcohols was studied at temperatures ranging from 60 to 250°, and enthalpy changes were calculated for the corresponding main reactions of typical alcohols.

The CI. reactivity is controlled by the temperature and the substrate structure as usual, and in addition, by the molecular size. The combination of thermal, structural and substrate‐size effects leads to the following main conclusions.

At low‐reactivity conditions, i.e. at 150° or less, the alcohols with less than 11 C‐atoms give four distinct types of spectra, with (M – OH)+ usually as the base peak. The characteristic ions are MC4H9+ and (M – H)+ for primary, MH+ and (MC4H9 – H2O)+ for secondary, (MC4H9 – H2O)+ for tertiary and allyl‐type alcohols. Configurational assignments of stereoisomeric alcohols are also possible, by means of steric compression and shielding effects. The MH+/(M – OH)+ ratio in the spectra of epimeric methylcyclohexanols is at least 3 to 4 times higher for the isomers with mainly axial OH‐group conformation compared to the equatorial isomers. Stereospecific (M ‐ H)+ ions are apparently formed from trans‐2‐methylcyclopentanol and endo‐norbornan‐2‐ol by a favorable abstraction of the unshielded H(α)‐atoms versus normal behavior of the other epimers.

While the spectra recorded at 200° show almost exclusively (M – OH)+ ions, those at 250° give nevertheless some C‐skeleton information through the temperature dependent decomposition of the (M – OH)+ ions.
Synthesis and Opiate Activityin vitroof Five Newp‐Nitrophenylalanine4‐Enkephalin‐like Peptides
Authors: Fauchère Jean‐Luc , Pfenninger Susanne , Do Kim Quang , Lemieux Carole , Schiller Peter W.
Published: December 2004

Converging data obtained in biochemical and pharmacological bioassays for opiate activity are presented for five new enkephalin‐like peptides. The main structural features of the analogues, the synthesis of which is described in detail, were the presence ofD‐alanine orD‐serine in position 2,p‐nitrophenylalanine in position 4 and of a freeC‐terminal carboxylic function. Confirming our previous observations [1], the substitution of phenylalanine byp‐nitrophenylalanine enhanced the overall opiate activity but decreased the selectivity towards m̈/δ‐receptor sites. Tyrosyl‐D‐alanyl‐glycyl‐p‐nitrophenylalanyl‐adamantylalanine was particularly potent in all assays while tyrosyl‐D‐seryl‐glycyl‐p‐nitrophenylalanyl‐leucyl‐threonine was very selective in the bioassays on isolated tissues and moderately selective in the binding assay. These results will have to be taken into account in future photoaffinity labelling and quantitative structure‐activity relationships (QSAR) studies.
Synthese von Carotinoiden mit hydroxylierter Methylgruppe an der Polyenkette mit Hilfe von Vinyl‐Anionen (Shapiro‐Reaktion)
Authors: Bütikofer Pierre‐André , Eugster Conrad Hans
Published: December 2004

Syntheses of Hydroxymethyl‐carotenoids Using Vinyl‐Anions Generated by the Shapiro‐Reaction

A versatile synthesis of hydroxymethyl‐carotenoids with β‐ or ϵ‐end groups is presented. It makes use of the reactive vinyl anions prepared by the Shapiro‐reaction from (phenylsulfonyl)hydrazones of polyenones and their smooth 1,2‐addition to polyenals. Thus, e.g. (3R,6′R)‐β, ϵ‐carotene‐3, 19‐diol (72), an optically active model compound structurally very close to loroxanthin (1), has been synthesized.
Stoffwechselprodukte von Mikroorganismen 221. Mitteilung. (3S, 8E)‐1,3‐Dihydroxy‐8‐decen‐5‐on, ein Stoffwechselprodukt von Streptomyces fimbriatus (MILLARD und BURR 1926)
Authors: Keller‐Schierlein Walter , Wuthier Damian , Drautz Hannelore
Published: December 2004

(3S, 8E)‐1,3‐Dihydroxy‐8‐decen‐5‐one, a Metabolite of Streptomyces fimbriatus (MILLARD and BURR 1926)

From the cultures of Streptomyces fimbriatus, strain Tü 2335, the title compound 1 was isolated by solvent extraction, chromatography, and distillation. Its constitution was determined by spectroscopic investigations of 1 and some of its derivatives, and the chirality by transformation to (R)‐1,3‐isopropylidenedioxy‐decane (12); a reference sample of the latter was prepared from (R)‐methyl 3‐hydroxydecanoate (10). In the equilibrium mixture the keto form 1 predominates the two hemiacetals 2a and 2b. Compound 1 is inactive against bacteria, yeasts and fungi.
Conformationally Controlled Odor Perception in ‘Steroid‐type’ Scent Molecules
Authors: Ohloff Günther , Giersch Wolfgang , Thommen Walter , Willhalm Bruno
Published: December 2004

A series of compounds possessing a ‘Steroid‐type’ scent and related to 4‐(4′‐t‐butylcyclohexyl)‐4‐methyl‐2‐pentanones (1 and 2) has been synthesized. The odor of these compounds has been found to be dependent on their conformation; only when the molecule can assume a steroid‐like shape there is an interaction with the odor chemoreceptor.
Angiotensin II Analogues. Part II. Synthesis and incorporation of the sulfur‐containing aromatic amino acids: L‐(4′‐SH)Phe, L‐(4′‐SO2NH2)Phe, L‐(4′‐SO)Phe and L‐(4′‐S‐CH3)Phe
Authors: Escher Emanuel , Bernier Michel , Parent Paul
Published: December 2004

L‐Phenylalanine has been treated with chlorosulfonic acid and the product was either hydrolyzed, ammonolyzed or reduced. The resulting sulfonic‐acid and aminosulfonyl derivatives have been employed for peptide synthesis with Boc‐protection of the Nα‐position only. The reduction product L‐(4′‐SH)Phe has been protected by formation of asymmetric disulfides or with various thiol protecting groups (benzyl‐, methyl‐ and acetamidomethyl groups, the latter being the most suitable for peptide synthesis).

With these protected amino acids several analogues of angiotensin II have been synthesized by the solid‐phase method. These analogues have been used for structure‐activity relationship studies on three different bioassays.
Dediazoniations of Arenediazonium Ions. Part XXI. Dediazoniation of Arenediazonium Ions Complexed with Crown Ethers
Authors: Nakazumi Hiroyuki , Szele Ivanka , Yoshida Katsuhira , Zollinger Heinrich
Published: December 2004

The evaluation of the dediazoniation kinetics of various m‐ and p‐substituted benzenediazonium tetrafluoroborates in 1,2‐dichloroethane at 50° in the presence of 18‐crown‐6, 21‐crown‐7 and dicyclohexano‐24‐crown‐8 demonstrates that the rate constant for the dediazoniation within the complex (k2) is smallest, and the equilibrium constant for complex formation (K) is largest for the complexes with 21‐crown‐7 (cf. Scheme 1). The logarithms of the equilibrium constants (K) for complex formation with each of the crown ethers studied correlate well with Hammett's substituent constants, σ, to give reaction constants ρ = 1.18–1.38.

A linear correlation between the logarithms of the rate constants for the dediazoniation within the complex with those of the dediazoniation rate constants of uncomplexed diazonium ions (log k2 vs. log.k1), found for most substituted diazonium salts, indicates that the dediazoniation mechanism of the complexed diazonium ions is not significantly different from that of the free ions. For very electrophilic diazonium ions (p‐Cl, m‐CN), k2 was much larger than expected on the basis of the linear log k2 vs. log k1 relationship. Analysis of the dediazoniation products showed that this was due to a change in mechanism from heterolytic to homolytic dediazoniation.

The complexation rate of diazonium salts by crown ethers (kc) is practically diffusion controlled and does not change much with the size of the crown ether. The decomplexation rate (kd), however, is significantly lower for complexes with 21‐crown‐7, than for those with 18‐crown‐6 and dicyclohexano‐24‐crown‐8, and is therefore the reason for the variations in the equilibrium constant (K) and thus for the fact that complexes of arenediazonium salts with 21‐crown‐7 are the most stable.

The amounts of the Nα‐Nβ rearrangement, as well as those of the exchange of the 15N‐labelled diazonio group with external nitrogen during dediazoniation of p‐toluenediazonium salt were independent of the addition of crown ethers.

A dediazoniation mechanism involving a charge transfer, as well as an insertion‐type diazonium ion‐crown ether complex is proposed. In this mechanism, dediazoniation of the insertion complex does not take place directly, but through the charge‐transfer complex.
Some Novel Nematic Materials Bearing Two Lateral Nitrile Functions
Authors: Kelly Stephen M. , Huynh‐Ba Tuong
Published: December 2004

More than fifty esters of 3‐alkyl‐6‐hydroxy‐1,2‐benzenedicarbonitrile have been prepared. The new esters exhibit stable nematic phases of high negative dielectric anisotropy. The relationship between the clearing points of the esters and the various rings they incorporate is the same as that normally observed for nematic materials of positive dielectric anisotropy.
1‐[(Dimethylamino)methyl]pyrrol aus Trimethyl (1‐pyrrolyl)‐ammonium‐Ion
Authors: Zeltner Peter , Bernauer Karl
Published: December 2004

1‐[(Dimethylamino)methyl]pyrrole from Trimethyl (1‐pyrrolyl)ammonium Ion

Trimethyl (1‐pyrrolyl)ammonium iodide (5a) and the corresponding p‐toluene‐sulfonate 5b are transformed by strong bases into 1‐[(dimethylamino)methyl]‐pyrrole (9), i.e. into a N‐Mannich base, a type of compound novel in the pyrrole series. In this reaction, which is very fast in DMSO, the cation of compounds 5 is deprotonated to form the nitrogen ylide 6. The latter undergoes a Stevens‐type rearrangement to 9. Several facts, namely the negative outcome of a cross‐reaction experiment with 3,4‐dimethylpyrrole and of an attempt to obtain 9 from pyrrole and dimethyl (methylidene)ammonium iodide in the presence of one equivalent of sodium methoxide, as well as unsuccessful CIDNP studies point to a rearrangement mechanism via the contact ion pair 12.
The Preparation of Optically Pure 7‐Oxabicyclo [2.2.1]hept‐2‐ene Derivatives. The CD Spectrum of (+)‐(1R)‐7‐Oxabicyclo [2.2.1]hept‐5‐en‐2‐one
Authors: Vieira Eric , Vogel Pierre
Published: December 2004

(−)‐1‐Camphanoyloxyacrylonitrile (=(−)‐1‐cyanovinyl camphanate; 1) obtained from the commercially available (−)‐camphanoyl chloride and 2‐oxo‐propiononitrile added to furan at 20° in the presence of Cu (BF4)2 · 6H2O or ZnI2 and gave a mixture of 2‐cyano‐7‐oxabicyclo [2.2.1]hept‐5‐en‐2‐yl camphanates (2–5) from which isomer 5 could be obtained pure by crystallization. The latter was transformed into (+)‐(1R)‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐one (6) in high yield and optical purity. Adducts 2–4 were recycled into 1+furan by heating in toluene, and (−)‐camphanic acid was recovered after saponification of 5. The absolute configuration of 6 was deduced from its CD spectrum which showed two 1200‐cm−1 Franck‐Condon series for its n→π transition.
A Total Synthesis of Aphidicolin: Stereospecific Synthesis of (±)‐3α, 18‐Dihydoxy‐17‐Noraphidicolan‐16‐one
Authors: Bettolo Rinaldo Marini , Tagliatesta Pietro , Lupi Alessandro , Bravetti Doriano
Published: December 2004

A simple, efficient, and stereospecific total synthesis of (±)‐3α, 18‐dihydroxy‐17‐noraphidicolan‐16‐one (2), by solvolytic rearrangement of the endo‐bicyclo‐[2.2.2]oct‐5‐en‐2‐yl methanesulfonate 16, is described. Since aphidicolin (1) has already been obtained from 2, the preparation of the latter formally constitutes a new total synthesis of 1.
Synthesis of Urinary Metabolites of Retinoic Acid
Authors: Kim Tong Hei , Kon Kenji , Isoe Sachihiko
Published: December 2004

Urinary metabolites 5‐methyl‐5‐[2‐(2,6,6‐trimethyl ‐3‐oxo‐1‐cyclohexen‐1‐yl)‐vinyl]‐2‐tetrahydrofuranone (1) and 5‐[2‐(6‐hydroxymethyl‐2, 6‐dimethyl‐3‐oxo‐1‐ cyclohexen‐1‐yl)vinyl]‐5‐methyl‐2‐tetrahydrofuranone (2) of retinoic acid have been synthesized from 4‐[2,2,6‐trimethyl‐3‐(tetrahydro‐2 H ‐pyran‐2‐yl)oxy‐1‐cyclohexen‐1‐yl]‐3‐buten‐2‐one (4) and methyl 2‐(3,3‐ethylenedioxy‐1‐butenyl)‐1, 3‐dimethyl‐4‐oxo‐2‐cyclohexene‐1‐carboxylate (5).
Nucleotide, XVIII. Synthese und Eigenschaften von (tert‐Butyldimethylsilyl)guanosinen, Guanosin‐3′‐phosphotriestern und Guanosin‐haltigen Oligoncleotiden
Authors: Flockerzi Dieter , Schlosser Wilhelm , Pfleiderer Wolfgang
Published: December 2004

Nucleotides, XVIII. Synthesis and Properties of (tert‐Butyldimethylsilyl)guanosines, Guanosine‐3′‐Phosphotriesters and Guanosine‐containing Oligonucleotides

Silylation of N2‐benzoyl‐ (1) and N2‐isobutyrylguanosin (2) by tert‐butyldimethylsilyl chloride led to the various mono‐, di‐ and tri‐O‐tert‐butyldimethylsilyl derivatives 3–15. The synthesis of 2′‐ (24–31) and 3′‐phosphotriesters (16–23 and 32) could be achieved by phosphorylations of partially protected guanosines. The guanosine‐3′‐phosphodiester 33 and the 5′‐OH‐guanosine‐3′‐phosphotriester 34 are used in condensation reactions as 5′‐ and 3′‐terminal components, respectively, to form dinucleoside mono‐ (39 and 40) and diphosphates (41–48) in relatively good yields. The various products were characterized by elemental analyses, 1H‐, 13C‐, and 31P‐NMR spectra as well as UV and CD spectra.
Metal Complexes with Macrocyclic Ligands, XVIII. A study of steric effects in the Co2+‐, Ni2+‐ and Cu2+‐complexes with 1‐(2‐aminoethyl)‐ and 1‐(2‐dimethylaminoethyl)‐4,8,11‐trimethyl‐1,4,8,11‐tetraazacyclotetradecane
Authors: Basak Arup. K. , Kaden Thomas A.
Published: December 2004

The two macrocycles 1‐(2‐aminoethyl)‐ and 1‐[2‐(dimethylamino)ethyl]‐4, 8, 11‐trimethyl‐1, 4, 8, 11‐tetraazacyclotetradecane, 1 and 2, respectively, and their metal complexes with Co2+, Ni2+ and Cu2+ were prepared. The different spectral properties of the complexes with these two ligands can be rationalized by assuming that, in the case of 1, the amino group of the pendant arm is axially coordinated to the metal ion giving a pentacoordinate structure, whereas the dimethylamino group of 2 cannot bind because of sterical hindrance. This is also corroborated by the observation that the complexes of 2 react with unidentate ligands such as N and SCN− to give ternary species MLX+, whereas those of 1 do not. This indicates that the complexes of 1 have no free coordination site, their coordination sphere being completely saturated by the five N‐atoms of the macrocycle, whereas the complexes of 2 having a vacant site still can add an unidentate ligand.
15N‐NMR study of activated enamines. Structural dependence of δ (15N) and nJ(N,H) in primary, secondary and tertiary enamino‐ketones, esters and amides
Authors: Kozerski Lech , Kamienska‐Trela Krystyna , Kania Lidia , Von Philipsborn Wolfgang
Published: December 2004

The pulse sequence INEPT was used to obtain proton‐coupled 15N‐NMR spectra in natural isotope abundance for enamines substituted in 2‐position with electron‐with‐drawing groups.

The chemical shifts and coupling constants are discussed in terms of their relationship to structural features such as multiple N‐alkyl substitution, double‐bond configuration, H‐bonding, N‐lone‐pair delocalization within the conjugated system, and steric effects.

It is concluded that 15N chemical shifts are a sensitive probe for local structural modifications at the N‐atom and conformational changes in a remote part of a conjugated molecule, while one‐bond N,H‐coupling essentially reflects N‐hybridization and subtle local geometric distortions. Stereospecific three‐bond N,H spin coupling to olefinic protons (4.0 ± 0.2 Hz) has been found a characteristic feature of (Z)‐isomers in all investigated compounds, whereas two‐bond coupling to olefinic protons (2J(N,H) = 0.5 to 5 Hz) is observed in (E)‐isomers. The sensitivity to solvents and steric properties of remote substituents renders geminal coupling a useful probe for studying electronic effects in the CN bond.
Photodecomposition of Liquid Water with TiO2‐Supported Noble Metal Clusters
Authors: Yesodharan Edapoikayil , Grätzel Michael
Published: December 2004

Rh‐ and Ru‐loaded TiO2‐particles were produced from cluster precursors (Rh6(CO)16, Ru3(CO)12) and their activity in mediating H2O‐decomposition through band‐gap excitation was investigated. Activity increases in the order Ru<RuO2<Rh≃Rh2O3. Bifunctional Rh/RuO2‐loaded TiO2 exhibits optimal performance with overall light‐to‐chemical‐energy conversion efficiency of 0.13%. Lack of O2‐appearance in the gas phase during photlysis observed with closed systems is due to photo‐uptake of O2 by the TiO2‐particles. In alkaline solution the capacity for O2‐uptake is surprisingly high and the nature of the stored O2 is tentatively identified as a μ‐peroxo‐bridged Ti‐species.
Spirocyclische 3‐Oxazoline durch 1,3‐dipolare Cycloaddition von Benzonitrilio‐2‐propanid mit 1,4‐Chinonen
Authors: Stegmann Werner , Uebelhart Peter , Heimgartner Heinz
Published: December 2004

Spiro 3‐Oxazolines from the 1,3‐Dipolar Cycloaddition of Benzonitrilio‐2‐propanide and 1,4‐Quinones

On irradiation with light of wavelength 290–350 nm, 2,2‐dimethyl‐3‐phenyl‐2H‐azirine (1b) reacts with 1,4‐naphthoquinone to give the 1H‐benzo [f]isoindol‐4,9‐dione (11) (Scheme 3) via cycloaddition of the benzonitrilio‐2‐propanide (2b) onto the quinone C, C‐double bond. With 2‐methyl‐ and 2,3‐dimethyl‐1,4‐naphthoquinone, the nitrile ylide 2b undergoes cycloaddition preferentially onto the C, O‐double bond of the quinone, leading to spiro‐oxazolines 12 and 14 (Scheme 4). Steric as well as electronic effects can be discussed to explain the observed site selectivity of the cycloaddition.

With the 1,4‐benzoquinones 15a, 15b, 15d and 15f, nitrile ylide 2b undergoes the 1,3‐dipolar cycloaddition exclusively onto the C, O‐double bond. The corresponding spiro‐oxazolines have been isolated in 17–32% yield. This contrasts with the previously reported results with benzonitrilipo‐phenylmethanide (2a), which undergoes cycloaddition to the C, C‐double bond of 1,4‐benzoquinones (cf. [1]). This difference in the site selectivity of the 1,3‐dipolar cycloaddition can be explained with Houk's concept of LUMO‐polarization, that is, the stronger nucleophilic dipol 2b polarizes the LUMO of a α,β‐unsaturated carbonyl compound more efficient than the less nucleophilic 2a. This leads to a preference of the cycloaddition to the C, O‐double bond in the case of 2b.

With 2,3‐dimethyl‐ (15c) and 2,3,5,6‐tetramethyl‐1,4‐benzoquinone (15e), nitrile ylide 2b undergoes C, O‐ as well as C, C‐cycloaddition (Schemes 7 and 8).
Über die Stereoselektivität der 9,9′‐Spirobifluoren‐kronenäther gegenüber α‐Aminoalkoholen
Authors: Prelog Vladimir , Mutak Stjepan
Published: December 2004

Stereoselectivity of 9,9′‐Spirobifluorene Crown Ethers towards α‐Amino Alcohols

Crown ethers I‐VI were tested by partition experiments for their stereoselectivity towards α‐amino alcohols 1–10. The stereoselectivity depends in a regular way on both the absolute and relative configuration of the crown ether and α‐aminoalcohol. Comments are made on some high stereoselectivities.
Synthese von Diterpenen als mögliche biogenetische Vorläufer des C20‐Carotinoides Crocetin
Authors: Schurtenberger Heidi , Vögeli Ulrich , Pfander Hanspeter
Published: December 2004

Synthesis of Diterpenes as Possible Biogenetic Precursors of the C20‐Carotenoid Crocetin

With regard to the investigation of the biosynthesis of the C20‐carotenoids in saffron the four diterpenes 6–9 were synthesized, who differ only in their degree of saturation. A detailed analysis of their 1H‐ and 13C‐NMR spectra has been achieved by their mutual comparison.
Silicon‐Directed Nazarov Reactions III. Stereochemical and Mechanistic Considerations
Authors: Jones Todd K. , Denmark Scott E.
Published: December 2004

The influence of remote substituents on the stereochemical outcome of electrocyclization in the silicon‐directed Nazarov reaction has been examined. While the degree of stereocontrol was modest (ca. 3:1) the substituent in the major isomer (4,5 or 7‐substituted cis‐hexahydroind‐2‐en‐1‐ones) is always cis to the protons on the ring fusion. Thorough spectroscopic and conformational analysis revealed that divergent senses of electrocyclization are responsible for the observed products. Additional experiments suggest that steric, rather than stereoelectronic forces control the sense of cyclization. A qualitative description of the nature of reactive intermediates in the silicon‐directed Nazarov reaction is proposed as well as an explanation for the remarkable efficacy of FeCl3 for inducing the reaction.
Identification de stérols à chaîne latérale oxygénée dans une éponge de l'espèce Hyrtios
Authors: Koch Patrick , Djerassi Carl , Lakshmi Vijai , Schmitz Francis J.
Published: December 2004

Thirty‐two sterols are identified in the sponge Hyrtios sp. In addition to fourteen monohydroxylated compounds, the sterol fraction contains eight functionalized sidechain sterols, three of them new: 3 β‐hydroxy‐24‐norchol‐5‐en‐23‐al (19), (22‐trans)‐3 β‐hydroxycholest‐5, 22‐dien‐24‐one (20) and (22R, 23R, 24S) or (22S, 23S, 24S)‐ 22,23‐epoxy‐24‐methylchoest‐5‐en‐3 β‐ol (24). The probable biological origin, rather than artifact production, of these undescribed components is discussed.
Umsetzung von 2‐Azidoalkoholen mit Trialkylphosphiten Bildung von Aziridinen und Amidophosphorsäureesten via Imidophosphorsäureester und 1,3,2λ5‐Oxazaphospholidine
Authors: Willeit Armin , Müller Ernst Peter , Peringer Paul
Published: December 2004

Reaction of 2‐Azidoalcohols with Trialkylphosphites. Formation of Aziridines and Amidophosphates via Imidophosphates and 1,3,2λ5‐Oxazaphospholidines

The 2‐azidoalcohols 1 and 2 react with trialkyl phosphites to trialkyl (2‐hydroxy‐alkyl)imidophosphates 10, 14, and 15 respectively, whereas the 2‐azidoalcohols 3‐7 yield the 2,2,2‐trialkoxy‐1,3,2λ5‐oxazaphospholidines 16–22 under the same reaction conditions (Scheme 2). The dialkyl (2‐hydroxyalkyl)amidophosphates 23, 25, and 27–34 are obtained by the reaction of 10, and 14–22 with water (Scheme 3 and 4). By reaction with alcohols, however, both the imidophosphates 10, 14 and 15 and the 1,3,2λ5‐oxazaphospholidines 16–22 are transformed to aziridines 24, 26, and 35–38 (Scheme 5). The reactions of the imidophosphates seem to proceed via 1,3,2λ5‐oxazaphospholidines.
Carbon Participation in the Solvolysis of Tertiary Norbornyl Derivatives Norbornanes. Part 15. 6‐substituted 2‐methylnorbornyl 2‐exo‐ and 2‐endo‐2,4‐dinitrophenyl ethers
Authors: Grob Cyril A. , Waldner Adrian
Published: December 2004

The solvolysis rates and products of the tertiary 2‐methyl‐2‐exo‐ and ‐2‐endo‐norbornyl 2,4‐dinitrophenyl ethers 1 and 2, (X = 2,4‐(NO2)22C6H3O) have been determined. The different sensitivities of the rates of these ethers to the inductive effect of substituents at C(6) indicate that graded bridging of C(2) by C(6) occurs in the ionization of the exo‐ethers 1, not, however, in the ionization of the endo‐ethers 2. In both cases hydrolysis leads to 2‐methyl‐2‐exo‐norbornanols only. Consequently, substitution takes place with retention at C(2) in the exo‐series 1 and with inversion at C(2) in the endo‐series 2. It is concluded that stereoelectronic and polar effects, rather than steric bulk effects, determine the high exo/endo rate ratios of the parent norbornyl derivatives 1a and 2a.
A Novel Three‐Carbon Ring Expansion Sequence Synthesis of Exaltone® and (±)‐Muscone
Authors: Fehr Charles
Published: December 2004

Intramolecular Grignard‐type reaction of the bromo lactones 3 and 8 affords the macrocycles 10, 11, 12 and 13, 14, 15, respectively. More efficiently, 10 and 13 are obtained by intramolecular nucleophilic attack of the carbanions derived from the sulfonyl lactones 20 and 22 and in situ reduction of the intermediate sulfones 21 and 23. The macrocylic hydroxy ketones 10 and 13 are converted into Exaltone® (2) and muscone (1), respectively.
A New Reaction of 1,2‐Dioxetanes. Formation of 1,2,4‐Trioxanes from Aldehydes
Authors: Jefford Charles W. , Boukouvalas John , Kohmoto Shigeo
Published: December 2004

1,2‐Dioxetanes bearing different 3‐phenoxy substituents add to aldehydes to give 1,2,4‐trioxanes in yields of 17–75% depending on the nature of the para‐phenyl substituent. Illustrations of this new reaction are described.
Propellanes. Part LXXI. Confirmation of predicted regiospecificity in Diels‐Alder reactions of certain propellanes with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione
Authors: Ashkenazi Pnina , Kaftory Menachem , Sayraç Tuǧmaç , Maier Günther , Ginsburg David
Published: December 2004

Two isomeric propellane epoxides 1a and 1b containing a cyclohexadiene ring are attacked by the title dienophile as predicted, syn to the five‐membered ether ring whose α‐hydrogens exert less repulsion than the α‐epoxy hydrogens or the epoxide oxygen, respectively, of the cyclobutane ring.
Hydroboration and Oxymercuration of Some 1‐Substituted Norborn‐2‐enes
Authors: Luef Wolfgang , Vögeli Ulrich‐Christian , Keese Reinhart
Published: December 2004

The 1‐substituted norborn‐2‐enes 11–13 and 18 react with electrophiles under kinetic control preferentially in 2‐position. The regioselectivity in oxymercuration is higher than in hydroboration and reaction with aqueous palladium chloride.
Chemie der Cumalinsäurederivate. I. Synthese und Diels‐Alder‐Reaktionen von 1‐Arylamino‐2‐methoxycarbonylbutadienen
Authors: Kvita Vratislav , Sauter Hanspeter , Rihs Grete
Published: December 2004

The nucleophilic attack of substituted anilines at position 6 of methyl coumalate (1) opens the α‐pyrone ring to form 4‐arylamino‐3‐(methoxycarbonyl)butadien‐1‐carboxylic acid 2 (Scheme 1). The latter are easily decarboxylated at room temperature in polar aprotic solvents to 1‐arylamino‐2‐(methoxycarbonyl)butadiene 4 which smoothly undergo regio‐ and stereospecific Diels‐Alder reactions with different dienophiles.
The Synthesis of (6 R*, 7 R*)‐4‐Carboxy‐3‐hydroxy‐7‐phenylacetamido‐2‐isooxacephem
Authors: Hakimelahi Gholam Hosein , Khalafi‐Nezhad Ali
Published: December 2004

A new route to the synthesis of the title compound is described.
(5R,6S,5′R,6′S)‐5,6,5′,6′‐Diepoxy‐β,β‐cartin: Sythese, Spectroskopische, chiroptische und chromatographische Eigenschaften
Authors: Acemoglu Murat , Eugster Conrad Hans
Published: December 2004

(5R,6S,5′R,6′S)‐5,6,5′,6′‐Diepoxy‐β,β‐Carotene: Synthesis, Spectroscopical and Chiroptical Properties, and HPLC‐Behaviour

Using the scheme C13 + C2→C15 + C10→C40, whereby C13 = (5R,6S)‐5,6‐epoxy‐β‐ionone [8], the title compound 11a, (R = H), has been prepared and characterized. It exhibits nearly identical CD spectra as violaxanthin (11b, R = OH).
On the Stereochemistry of Natural Irones, Dihydroirones, and their Precursors
Authors: Krick Wolfgang , Marner Franz‐Josef , Janicke Lothar
Published: December 2004

Natural irones from the essential oil of Iris rhizomes develop by oxidative degradation of C31‐triterpenoids produced by the plant. Two enantiomeric forms of irones are found in Iris, oils of different origin. The optical properties and CD spectra of irones, dihydroirones and their C31‐precursors are reported and their absolute stereochemistry is determined.
On the Stereochemistry of Irones
Authors: Rautenstrauch Valentin , Willhalm Bruno , Thommen Walter , Ohloff Güther
Published: December 2004

In view of the demonstration by Janeicke et al. that different Iris varieties produce enantiomeric irones [6], we complement our 1971 paper on the stereochemistry of the irones [3]. (1) We give what information we have on the origin of the Iris oil used in [3]; (2) we sow that we and Ruzicka et al. on whose degradation work our determination of the C(2)‐configurations was based hd the same irones in hand; (3) we summarize independent assignments of the C(2)‐configurations and the relative configurations of the α‐irones. (4) We also describe the indentification of a trace of the missing trans‐γ‐irone in our oil, and (5) revise the preferred conformation of the cis‐α‐irones in solution.
The photooxygenation of Δ9(11)‐dehydroestrone and its 3‐methyl ether potochemical reactions XX. Preliminary communication
Authors: Lupón Pilar , Grau Farran , Bonet Juan‐Julio
Published: December 2004

The photosensitized oxygenation of Δ9(11)‐dehydroestrone yields a complex mixture mainly of unstable compounds, while its 3‐methyl ether gives 3‐methoxy‐9, 17 ‐dioxo‐ 9,11‐seco‐1,3,5(10)‐estratrien‐11‐al, in good yield.
Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Struktur des proteinfreien Faktors
Authors: Livingston Douglas A. , Pfaltz Andreas , Schreiber Jakob , Eschnmoser Albert , Ankel‐Fuchs Dorothe , Moll Johanna , Jaenchen Rolf , Thauer Rudolf K.
Published: December 2004

Factor F430 from Methanogenic Bacteria: Structure of the Protein‐free Factor

Factor F430, the porphinoid nickel‐containing coenzyme of the methylcoenzyme‐M reductase of metanogenic bacteria is shown to be the 33,83,122,133,182‐pentaacid derivative of the pentamethylester F430M, the structure of which had been determined previously (see structural formulae 1 and 2). The structure assignment rests on chromatographic, UV/VIS‐, CD‐, IR‐, and 13C‐NMR‐spectroscopic as well as FAB‐mass spectral comparision of F430 with F430M and the pentaacid prepared by acid‐catalyzed hydrolysis of F430M.

In the cells of Methanobacterium thermoautotrophicum, factor F430 is present in a ‘bound’ and also, depending on the growth conditions, in ‘free’ form, the latter being defined as the part of total F430 that can be extracted from the cells under extremely mild conditions (80% EtOH at 0–4°). From the (protein)‐‘bound’ form, F430 is extracted by subsequently treating the cells at 0–4° with 80% EtOH containing (e.g.), 2m LiCi.

From both sources, the extracted factor is the same pentaacid, and there is no indication for the existence of a protein‐free F430 species that would contain additional (covalently bound) structural elements.
Parallelism Between Nucleophilically Solvent‐Assisted and Phenyl‐Assisted Reactions. Possible Existence of Nucleophilically β‐Phenyl‐Solvated Ion Pairs
Authors: Laureillard Jeane , Casadevall André , Casadevall Eliette
Published: December 2004

Solvolysis rate constants in MeOH and t‐BuOh are compared for β‐methyl and β‐phenyl derivatives of two cycloakyl systems. It appears that the β‐phenyl derivatives solvolyse at te same rate as the β‐methyl ones. The lack of deceleration is attributed to phenyl assistance. It is established by configurational analysis of the reaction products, that those products which necessarily originate from a cationic species are the most abundant ones. It is suggested that these reactions could proceed through ion‐pair intermediates, which are nucleophilically solvated by phelyl or by the solvent. A parallel between phenyl assistance and ‘SN2 (intermediate)’ mechanism, suggested by Bentely & Schleyer, is drawn.
Boron‐nitrilotriacetate, N(CH2COO)3B: Synthesis and Crystal‐Structure Determinations at 293K and 110K
Authors: Müller Edgard , Bürgi Hans‐Beat
Published: December 2004

The title compound is insoluble in aprotic solvents and decomposes in protic ones. Its crystal structure consists of discrete molecules with non‐crystallographic C30‐symmetry and a transannular dative BN bond (1.620(3) (Å). The molecules pack tightly (density 1.804 g cm−2) interacting via O…C contacts between carbonyl groups (2.92–3.05 Å)). The atoms show small vibrational motion which may be interpreted in terms of a rigid body model. Distances and angles obtained at 293 and 110 were corrected for effects of rigid body motion and do not show significant differences.
First Direct Synthesis of Optically Active 3‐Methylcyclopentene
Authors: Silwka Hans‐Richard , Hansen Hans‐Jürgen
Published: December 2004

(−)‐(S)‐ and (+)‐(R)‐3‐methylcyclopentene (1) has been prepared in a stereochemically unambiguous synthesis. The (S)‐configuration for (−)‐1 was confirmed by correlation with (−)‐(S)‐1‐methylindane.
Die diasteromeren Aurochrome: Synthese, Analytik und Chiroptische Eigenschaften
Authors: Acemoglu Murat , Eugster Conrad Hans
Published: December 2004

The Diastereomeric Aurochromes: Their Synthesis, Analysis and Chiroptical Properties

(all‐E)‐Aurochrome (5,8:5′,8′‐diepoxy‐5,8,5′,8′‐tetrahydro‐β,β‐carotene; 1) has two pairs of constitutionally identical chiral centres and, therefore, is expected to exist in four pairs of enantiomers and two meso‐forms. Using starting materials with well‐defined configuration, we performed the syntheses of the following pure aurochromes: (5R,8R,5′R,8′R)‐aurochrome (2) and its racemate, Meso‐(5R,8R,5′S,8′S)‐aurochrome (3), (5 R,8 S,5′ R,8′ S)‐aurochrome (4) and its racemate, meso‐(5R,8S,5′S,8′R)‐aurochrome (5), (5R,8R,5′R,8′S)‐aurochrome (6) and its racemate. The (5RS,8RS,5′SR,8′RS)‐aurochrome (7) was detected chromatographically, using a HPLC system that allows clean separation of the four racemic‐ (or optically active) and the two meso‐aurochromes. The optically active autochromes 2 and 4 exhibit non‐conservative CD spectra with strong Cotton effects of opposite but not mirror‐like tracings. Solutions of aurochromes in CHCl3, in the presence of HCl, undergo epimerization at C(8). Those epimers with CH3 trans to C(9) slightly predominate under equilibrium conditions. Deprotonation of the phosphonate (±)‐14 with strong base causes isomerization at the terminal oxirane into a dihydrofuran. This reaction allowed convenient syntheses of the diastereoisomeric aurochromes (±)‐2, 3, (±)‐4, 5, (±)‐6, and (±)‐7 and of (5RS, 8RS)‐ and (5RS, 8SR)‐12′‐apo‐aurochrome‐12′‐als (21 and 22, respectively).
Synthese eines cyclischen Depsipeptides mittels Amidcyclisierung
Authors: Obrecht Daniel , Heimgartner Heinz
Published: December 2004

Synthesis of a Cyclic Depsipeptide via an Amide Cyclization

The synthesis of (S)‐Pms‐(R)‐Pro‐(S)‐Ala‐Aib‐N(CH3)2 (12) has been achieved according to Scheme 3. For the formation of fragment 11, the reaction of Z‐alanine (Z = benzyloxycarbonyl) and 3‐dimethylamino‐2,2‐dimethyl‐2‐azirine (1) has been used, whereby 1 serves as an aminoisobutyric‐acid dimethylamide (aib‐N(CH3)2) equivalent. Treatment of a suspension of 12 in toluene with HCl gas at 100° led to the cyclic depsipeptide 13 in 72% yield (Scheme 4). In presence of water, the acid 14 was isolated as the sole product. A mechanism for the formation of 13 and 14 via an oxazolinone intermediate, is postulated in Scheme 4.
Isolierung und Struktur von Pteridinen (Lumazinen) aus Russula sp. (Täublinge; Basidiomycetes)
Authors: Iten Peter Xaver , Märki‐Danzig Hana , Koch Herbert , Eugster Conrad Hans
Published: December 2004

Isolation and Structure Elucidation of Pteridines (Lumazines) from Russula sp. (Basidiomycetes)

Extensive chromatogaphic separations and spectroscopic investigations have led to the isolation and identification of several water‐soluble pteridines from Russula sp., the so‐called russupteridines, namely: 1‐(5‐amino‐2‐6‐dioxo‐1,2,3,6‐tetrahydeopyrimidin‐4‐yl)amino‐1‐deoxy‐D‐ribitol (1; a pro‐lumazine; first identification in a basidiomycete(; l‐deoxy‐l‐(6‐methyl‐2‐4,7‐trioxo‐1,2,3,4,7,8‐hexahydro‐pteridin‐8‐yl)‐D‐ribitol (3) and l‐deoxy‐1‐(2,4,7‐trioxo‐1,2,3,4,7,8‐hexahydeopteridin‐8‐yl)‐D‐ribitol (4); both compounds found for the first time in higher fungi; they belong to the components with the strongest violet‐blue fluorescence in Russula sp.; riboflavine (6; now recognized as an important yellow colorant in a great many of Russula sp.); russupteridine‐yellow I (= l‐(6‐amino‐7‐(N‐fromylimino)‐2,4‐dioxo‐1,2,3,4,7,8‐hexahydropteridin‐8‐yl)‐1‐deoxy‐D‐ribitol; 5; a component with very strong fluorescence; the first derivative of the novel 6,7‐diamino‐lamazine); russupteridine‐yellow IV (= l‐deoxy‐1‐)(2,6,8‐trioxo‐2,4,5,6,7,8‐hexahydro‐1H‐imidazolo[4,5‐g]pteridin‐4‐yl)‐D‐ribitol (7)). Two further yellow russupteridines (yellow II and Yellow V) with very strong fluorescence have been isolated and characterized.
Synthesen von Aminolumazinen
Authors: Märki‐Danzig Hana , Eugster Conrad Hans
Published: December 2004

Syntheses of Aminolumazines

6‐aminolumazien 2 (1‐(6‐amino‐2,4,7‐trioxo‐1,2,3,4,7,8‐hexahydropteridin‐8‐yl)‐1‐deoxy‐D‐ribitol), a degradation product of russupteridine‐yellow I (1) has been prepared from l‐deoxy‐l‐(2,4,7‐trioxo‐1,2,3,4,7,8‐hexahydeopteridin‐8‐yl)‐D‐ribitol (5) via the azo compound 6 and its reduction with Sn/HCOOH. Condensation of 5‐amono‐6‐(D‐ribitylamino)uracil (8) with parabanic acid (9) has led to ta synthesis of russupteridine‐yellow IV (4); l‐deoxy‐l‐(2,6,8‐trioxo‐2,4,5,6,7,8‐hexahydro‐lH‐imidazolo[4,5‐g]pteridin‐4‐yl‐D‐ribitol), albeit in low yield.
Synthesen, chemische und elektrische Eigenschaften von Tetrathiafulvalen mit 1,6‐Methano[10]annulen‐Partialstruktur und von Chalcogendiimid‐derivaten
Authors: Neidlein Richard , Droste‐Tran‐Viet Dao , Gieren Alfred , Kokkinidis Michail , Wilckens Rudolf , Geserich Hans‐Peter , Ruppel Wofgang
Published: December 2004

Syntheses, Chemical and Electrical Properties of Tetrathiafulvalene with a 1,6‐Methano[10]annulene Moiety and of Chalcogendiimide‐Derivatives

The synthesis of the tetrathiafulvalene 6 has been described: the reaction of 1 with the benzenedithoil 2 yielded the bis‐dithioacetal 3 of 1,6‐methano[10]annulene‐dicarbaldehyde 1. The oxidation of 3 in the presence of HBF4 in Et2O yielded the salt 4, elimination of a hydride anion with triphenylmethylium tetrafluoroborate the salt 5, and elimination of a proton in 5 with Et3N the tetrathiafulvalene 6 with a 1,6‐methano[10]annulene moiety. The spectroscopic and electrochemical properties of 6 are described, and also the syntheses and properties of charge‐trasnfer complexes 7 and 8, including the properties of electric conductivity of 7 and 8. the syntheses of 9‐13 are reported and also their spectroscopic properties.
Structural Studies of Crystalline Pentacalent Organobismuth Compounds
Authors: Barton Derek H. R. , Charpiot Brigitte , Dau Elise Tran Huu , Motherwell William B. , Pascard Claudine , Pichon Clotilde
Published: December 2004

The syntheses and X‐Ray analyses of three pentavalent organobismuth compounds are described; one of these compounds has a novel diphenylbis(trifluoroacetato)‐bismuthate anion with trigonal bipyramidal geometry and a stereochemically active lone pair. Analysis of these structures together with other data from the literature allows a mapping of the reaction coordinate for bismuth polyhedra.
Stereoselective Introduction of Steroid Side Chains. Synthesis of Chenodeoxycholic Acid
Authors: Wovkulich Peter M. , Batcho Andrew D. , Uskoković Milan R.
Published: December 2004

A new short route to chenodeoxycholic acid has been developed. The synthesis is based on the stereoselective introduction of the steroidal side chain via an ene reaction of methyl acrylate and a (17Z)‐ethylidene steroid prepared from androstenedione.
Synthese und Kristallstruktur der Hydroxy‐lactone von 6‐Methyl‐2‐propionyl‐ und 3‐Methyl‐2‐propionylbenzoesäure
Authors: Rudinger‐Adler Edith , Hostettmann Maryse , Gramlich Volker , Petter Walter
Published: December 2004

The isomers 6‐methyl‐2‐propionyl‐ and 3‐methyl‐2‐propionylbenzoic acid were synthesized and separated by DCC (droplet counter‐current) chromatography. The crystal structure analyses showed that these compounds are hydroxylactones in the solid state.
Estimation of Dimerisation Constants from Complexatin‐Induced Displacements of 1H‐NMR Chemical Shifts: Dimerisation of Caffeine
Authors: Horman Ian , Dreux Bernard
Published: December 2004

The determination of the dimerisation constant (KD) for the weak self‐association of a compound C in dilute solution according to the equilibrium, 2C⇌C2 is described. The method uses chemical shifts measured on a series of solutions of C at different concentrations: the optimum KD is defined by a linear regression best‐fit procedure, which simultaneously determines optimum values for δo and also for δ∞, the intrinsic chemical shifts for nuclei in the monomer and dimer species. The dimerisation of caffeine in D2O is used as a model to demonstrate the working of the method and the quality of results obtained. The most probable value of KD for caffeine at 30.5° is found in the range 5.5–6.0 kg solution · mol−1, and the enthalpy and entropy of dimerisation are found to be ΔH⊖ = −15.1 kJ · mol−1 and ΔS⊖ = −35.3 J · °C−1 · mol−1, respectively. The influence of small errors in δo on the confidence limits of KD is discussed.
Voltammetrische Untersuchungen der Oxydation der symmetrischen Triazacarbocyanine in Acetonitril
Authors: Hellrung Bruno
Published: December 2004

Voltammetric Investigations on the Oxidation Step of Symmetrical Triazacarbocyanine Dyes in Acetonitrile Solution

The oxidation behaviour of twelve symmetrical triazacarbocyanine dyes with different heterocycles in MeCN (containing tetrabutylammonium perchlorate) has been investigated by means of dc‐, ac‐ and cyclic triangular wave voltammetry. The oxidation mechanism has been found to be of the type ec, with the electrochemical step being reversible to irreversible. Oxidation potentials and transfer coefficients have been measured (E1/2 1.60 to 2.12 V vs. Ag/AgCl) and compared with known properties of carbocyanines. The effect of substituents X has been studied on the compounds 1,3‐diethyl‐2‐[3‐(1,3‐diethyl‐5‐X‐benzimidazolin‐2‐ylidene)‐1‐triazeno]‐5‐X‐benzimidazolium tetrafluoroborate ((1a(X)) and 3‐ethyl‐2‐[3‐ethyl‐5‐X‐Δ4‐1,3‐thiazolin‐2‐ylidene)‐1‐triazeno]‐5‐X‐1,3‐thiazolium tetrafluoroborate (1g(X)), and ρ‐values of 0.425 and 0.565 V, respectively, have been found.
Photochemical reactions, 135th communication Photochemistry of Homoconjugated Cyclobutanones. II. Decisive Effect of gem‐ Dimethyl Substitution on the Course of the Oxa‐di‐π‐methane Rearrangement
Authors: Lyle Terry A. , Mereyala Hari Babu , Pascual Alfons , Frei Bruno
Published: December 2004

The synthesis and photolysis of the spirocyclobutanones 4–7 incorporating a cyclohexa‐, cyclohepta‐ and cyclooctadiene moiety, respectively, is described. On triplet excitation, these compounds undergo isomerization via a 1,2‐acyl shift involving one or both double bonds of the diene system. The presence of a gem‐dimethyl group as in 1, 4 and 7 dramatically changes the photoproduct distribution, since only these substrates leads to the products 3, 29 and 34 resulting from vinylogous ring closure (Scheme 5). Those substrates without methyl substitution (5 and 6) give only products of a rearrangement involving one double bond.
High performance liquid chromatography (HPLC) of natural products part VI. Sulfoxides of penicillin N and cephalosporin c and their role in biosynthesis of β‐lactam antibiotics
Authors: Kukolja S. , Miller R. D. , Duckworth D. C. , Dorman D. E. , Huckstep L. L. , Neuss Norbert , Quenner S. W.
Published: December 2004

Pure pencillin N α‐sulfoxide (1) and penicillin N β‐sulfoxide (2) were obtained by HPLC and tested as substrates for deacetoxycephalosporin C synthetase (DXCS). Neither one of the sulfoxides was utilized under conditions of conversion of penicillin N (8) to deacetoxycephalosporin C (9). The cephalosporin C α and β‐sulfoxides (3 and 4, resp.) were also prepared. Relative stabilities of the sulfoxides 3 and 4 are discussed by interpretation of the 13C‐NMR spectra.
Die Busseine C, D, E, F, G, H, J, K, L und M, zehn neue Tetranortriterpene aus Entandrophragma bussei Harms.
Authors: Guex Matthias , Tamm Christoph
Published: December 2004

The Business C,D,E,F,G,H,J,K,L und M, Ten New Tetranortriterpenes from Entandrophragma Bussei Harms

Ten new tetranortriterpenes, busseins C, D, E, F, G., H, J, K, L and M have been isolated from the petroleum ether extract of the timber of Entandrophragma bussei Harms. utilizing separation by high‐pressure liquid chromatography (HPLC). The structural assignments are based mainly on spectral evidence. For the 1H‐NMR spectroscopy extensive use of nuclear Overhauser effects (NOE) was made.
The Synthesis of cis‐ and trans‐ 7‐Phenylkacetamido‐O‐2‐isocephem
Authors: Hakimelahi Gholam Hosein
Published: December 2004

The synthesis of the title compounds is described.