bluuebunny/crossref_metadata_2025 huggingface dataset:
Über 1, 12‐Dioxa‐[12]paracyclophan‐Derivate mit einer Pseudoasymmetrieebene
Authors: Helmchen G. , Prelog V.
Published: December 2004

ansa‐Compounds Xa and b have been synthesized as first examples of diastereomers with a plane of pseudoasymmetry. Tentative configurations have been assigned to them on the basis of their NMR. spectra.
Ein neues Bufadienolid aus Helleborus odorus Waldtst. et Kit.. Über Krötengifte, 40. Mitteilung
Authors: Hauser E. , Linde H. H. A. , Živanov D.
Published: December 2004

Die Struktur von 14‐Hydroxy‐3‐oxo‐5α,14β‐bufa‐20,22‐dienolid (= 5αBufalon) 1 wird abgeleitet.
The Ring Expansion – Ring Contraction Dichotomy in Aromatic Nitrene and Carbene Reactions I. Arylcarbenes. Preliminary communication
Authors: Wentrup C. , Mayor C. , Gleiter R.
Published: December 2004

Rearrangement experiments and energy calculations by the CNDO/2 and extende Hückel methods indicate that ring expansion and ring contraction in aromatic carbenes and nitrnes can be one‐step processes which are governed by the stabilities of the primary products and the energies of the reactants.
The Photochemical and Thermal Interconversion of Some Cyclopentadienone Dimers
Authors: Klinsmann U. , Gauthier J. , Schaffner K. , Pasternak M. , Fuchs B.
Published: December 2004

In continuation of previous work on cyclopentadienone dimers [3], thermal and photochemical interconversions of the isomeric diketones 1, 3, and 5 by skeletal rearrangements have been established to the extent summarized in schemes 2 and 3, and the intramolecular [2+2] cycloaddition 1 → 2 was found to be reversible photochemically.
Nachbargruppenbeteiligung bei massenspektrometrischen Fragmentierungsreaktionen: Spermin‐Derivate. 18. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen
Authors: Schöpp E. , Hesse Manfred
Published: December 2004

The mass spectral behaviour of tetraacetyl spermine (2) has been investigated. The fragmentation reactions are characterized by the neighbouring group participation of the amide nitrogen atoms. Only a few reactions can be explained by usual pathways (α‐cleavage, onium reactions). Most of the fragment‐ions are formed by neighbouring group participation:

[M‐COCH3]+‐Ion.

Breakdown of one of the two 1,3‐diaminopropan moieties: m/e 242, 256, 268. This type of fragmentation is characteristic for all acetylated 1,3‐diaminopropan‐derivatives e.g. triacetylspermidine.

Expulsion of a neutral amine: m/e 169.

SNi‐type reactions, by which cyclic ions are formed: m/e 100.
Etude par spectrométrie de masse de C‐méthylinositols
Authors: Buchs A. , Charollais E.
Published: December 2004

The mass spectra of C‐methyl‐inositols and of two of their deuterium‐labelled analogues have been studied. The results indicate that each stereoisomer can be characterized by its mass spectrum. A fragmentation scheme based upon high‐resolution measurements, metastable peaks and deuterium‐labelling is proposed.
Structure of Wortmin, a new Metabolite from Penicillium wortmanni
Authors: Merlini L. , Mondelli R. , Nasini G. , Hesse Manfred
Published: December 2004

The structure of ester of 2‐hydroxy‐4‐methoxy‐6‐methylbenzoic acid with 6‐acetoxy‐7‐hydroxy‐7‐methyl‐3‐propenyl‐3,4,5,6,7,8‐hexahydro‐1H‐benzo[e]pyran‐8‐one (1) is assigned to wortmin, a new member of the sclerotiorin group of metabolites, produced by Penicillium wortmanni Klöcker.
The Nitrosation of Primary Aliphatic Diazocarbonyl Compounds: Formation of α‐carbonyl nitrile oxides. Preliminary communication
Authors: Dahn Hans , Favre B. , Leresche J.‐P.
Published: December 2004

Aqueous nitrosation of primary α‐carbonyl diazo compounds (ethyl diazoacetate, diazoacetone, diazoacetophenones) yields α‐carbonyl nitrile oxides, RCOCNO; their formation is demonstrated by 1,3‐dipolar addition reactions.
Über den enzymatischen Hydroperoxidabbau in Cerealien Enzymcharakterisierung und Reaktionsprodukte
Authors: Heimann W. , Dresen P.
Published: December 2004

Durch Haferenzymextrakte erfolgt bei Linolsäurchydroperoxiden (LHPO) sowohl ein Abbau der Hydroperoxidgruppe als auch der Dienstruktur. Die Umsetzung der Hydroperoxide verläuft enzymatisch (Isomerase) und führt nach Hydrolyse zur Bildung von 9,12,13‐Trihydroxy‐trans‐10‐octadecensäure und 9,10,13‐Trihydroxy‐trans‐11‐octadecensäure.
Stabilities and Near UV. Charge transfer spectra of binuclear and heterobinuclear complexes of N,N′‐bis‐[2‐(2‐pyridylmethyl‐amino)‐ethyl]‐oxamide with transition‐metal ions
Authors: Buxtorf Urs‐Peter , Zuberbühler Andreas
Published: December 2004

The formation of complexes of N,N′‐bis‐[2‐(2‐pyridylmethyl‐amino)‐ethyl]‐oxamide (PAOH2) with Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ has been studied potentiometrically and spectrophotometrically. Besides mononnclear species, PAOH2 forms the binuclear or heterobinuclear complexes Cu2(PAOH2)4+, Cu2PAO2+, Zn2PAO2+, CuNiPAO2+, and probably CuZnPAO2+ Some of these five compounds show an UV. absorption band near 350 nm reminiscent of that to dimeric copper acetate. The results suggest that charge transfer from the oxamidato group to Cu2+ is responsible for the near UV. absorption.
Der Mechanismus der Addition von Nucleophilen an Alkinderivate mit Push‐pull‐Gruppen
Authors: Neuenschwander Markus , Bigler Peter
Published: December 2004

The mechanism of the addition of nucleophiles to alkyne‐derivatives 1 having both push‐ and pull‐groups yielding Michael‐adducts is investigated. The rate of the second‐orderreaction increases (a) with increasing nucleophilic character of the amine and alcohol respectively, (b) with increasing electrophilic character of the alkyne‐derivatives 1, and (c) with increasing solvent polarity. These results support as rate‐determining step an attack of the nucleophile at C(3) of the alkyne‐derivatives.
Modellberechnung der EMK und der Ionenselektivität von Membranelektroden‐Messketten
Authors: Wuhrmann H.‐R. , Morf W. E. , Simon W.
Published: December 2004

Based upon a set of clearly specified assumptions, a universal integral equation is derived which describes the steady‐state EMF of an electrochemical cell containing any type of ion‐selective membrane electrode. The various modes of delineating the phenomenon ion‐selectivity by an explicit function are shown. For all types of analytically important ion‐sensitive electrodes, the selectivity between monovalent cations and anions, respectively, can be neatly and comprehensively rationalized. These theoretically derivable expressions are compiled.
The Ionization Potentials of Butadiene, Hexatriene, and their Methyl Derivatives: Evidence for through space interaction between double bond π‐orbitals and non‐bonded pseudo‐π orbitals of methyl groups?
Authors: Beez Michael , Bieri Gerhard , Bock Hans , Heilbronner Edgar
Published: December 2004

It is shown that the correlation of the π‐ionization potentials of ethylene (1), butadiene (2) and trans‐1,3,5‐hexatriene (4) favours the orbital sequence π, π, σ in butadiene and π, π, σ, π in the hexatriene in excellent agreement with the results of SPINDO calculations. Within the experimental error the π‐ionization potentials of cis‐1,3,5‐hexatriene (3) and trans‐1,3,5‐hexatriene (4) are the same. Methyl‐substitution of 2 lowers the π‐ionization potentials I1(π) and I2(π). For 1 and/or 4 substitution the difference I2(π)−I1(π) remains constant (≈ 2.5 eV). On the other hand 2 and/or 3 substitution leads to a smaller gap of I2(π)–I1(π) ≈ 1.6 to 2.0 eV without changing the mean π‐ionization potential I(π) relative to the corresponding 1,4 substituted derivatives. This result is rationalized in terms of a through space interaction between double bond π‐orbitals and non‐bonded pseudo‐π‐orbitals of the substituting methyl groups.

The reduced split I2(π)–I1(π) in cyclopentadiene is attributed to hyperconjugation across the methylene group.
Synthesis of Bridged Bicyclic Molecules using Halocarbenes. Derivatives of bicyclo[4.2.1]nonane
Authors: Jefford Charles W. , Burger Ulrich , Delay François
Published: December 2004

The addition of dichlorocarbene (generated by the interaction of sodium methoxide and ethyl trichloroacetate) to bicyclo[3.2.1]oct‐2‐ene, its 3‐chloro and exo‐3,4‐dichloro derivatives gives the exo 1 : 1 adducts in yields of 94, 89 and 48%. By suitable chemical reactions of these adducts, convenient syntheses of bicyclo[4.2.1]nona‐2,4‐diene and bicyclo[4.2.1]non‐3‐ene, together with their monochloro, dichloro and trichloro derivatives are obtained. Bicyclo[4.2.1]‐nonan‐3‐one is also obtained from bicyclo[4.2.1]non‐3‐ene in a synthesis starting from the readily available 5‐hydroxymethylnorborn‐2‐ene in an overall yield of 20%.
An Alkyl‐Aluminium Promoted Stereospecific Addition to Vinyl Olefins
Authors: Stefani Annibale
Published: December 2004

The reaction of tris‐crotyl‐boron with vinylic olefins in the presence of triethyl‐aluminium, results in the addition of an α‐methylallyl group and an aluminium atom to the double bond, as indicated by the hydrolysis products. The stereochemical aspect of the reaction is discussed and a mechanism is proposed to explain the preferential formation of one diastereoisomer.
Synthese und Eigenschaften von Isopterinnucleosiden ‐ Strukturanaloga des Cytidins. Nucleoside, X [1]
Authors: Harzer Klaus , Pfleiderer Wolfgang
Published: December 2004

Isopterin (1), its 6,7‐diphenyl (2) and 4‐dimethylamino derivative (3) react after silylation by hexamethyldisilazane with halogenoses 7 and 8 to the blocked isopterin‐N‐1‐nucleosides 9, 10, 11, 20 and 22, which form the free ribosides 12, 13 and 14 and 2‐desoxyribosides 21 and 23 on saponification. The easy nucleophilic substitution of the 4‐amino substituents allows the synthesis of further derivatives (15) as well as formation of lumazine nucleosides (17 and 18) by alkaline hydrolysis. The structures of the new compounds have been elucidated by UV. and NMR. spectroscopic investigations.
Organic Phosphorus Compounds 60. The direct synthesis of tris(N‐substituted carbamoylethyl) phosphine oxides
Authors: Maier Ludwig
Published: December 2004

The reaction of elemental white phosphorus with N‐alkyl acrylamides and N,N‐dialkyl acrylamides in the presence of a base is described and the physical properties of 8 new tertiary phosphine oxides of general formula (R2NCOCH2CH2)3PO (R = H, CH3, C2H5,(CH2)4, (CH2)5, and C2H4OC2H4, CH2CHCH2) are reported. Interaction of white phosphorus with RNCS, RNCO, azo‐bis‐isobutyronitrile, Ph2NNPh2, vinyl acetate, vinyl ethyl ether, and expoxides has also been investigated.
Organic Phosphorus Compounds 61. Esterification and chlorination of nitrilo‐tri(methylene‐phosphonic acid), N(CH2PO3H2)3, and hydroxyethylidenediphosphonic acid, H2O3PC(OH)(CH3)PO3H2, and the corresponding esters
Authors: Maier Ludwig
Published: December 2004

Nitrilo‐tri(methylenephosphonic acid) and hydroxyethylidenediphosphonic acid are esterified in high yield when treated with excess orthoformic acid ester under reflux. Because of the high temperature necessary to effect esterification a partial isomerization of hydroxyethylidenediphosphonate to the phosphate‐phosphonate isomer V takes place. Chlorination of N(CH2PO3H2)3 or a mixture of the ester and the acid with PCl5 yields tris(chloromethyl)amine, N(CH2Cl)3. Interaction of N(CH2Cl)3 and (EtO)3P yields nitrilo‐tri(methylenephosphonate), which on hydrolysis with HCl conc. produces N(CH2PO3H2)3. Chlorination of a mixture of hydroxyethylidene‐diphosphonic acid and the corresponding ethyl ester IV which contained the phosphate‐phosphonate isomer V gave the products VII to XI. Chlorination of the acid III with PCl5 gave 4 products, i.e., VIII, IX, XI and Cl2(O)POP(O)Cl2. The 1H‐ and 31P‐NMR. spectra of the products are discussed.
Die Addition von Säuren an Alkinderivate mit Push‐pull‐Gruppen,
Authors: Niederhauser Andreas , Neuenschwander Markus
Published: December 2004

The addition of proton acids as HF, HCl, HBr, HOAc and phenol to alkyne‐derivatives of the type (CH3)2NCCCOR(1) yielding the adducts 2 to 6 is investigated. The stereochemical course of the reaction is mainly influenced by the structure of the alkyne 1. Kinetic investigations show that the rate of the third‐order‐reaction increases from 1 a (RH) to 1 b (R  CH3) and 1 c (R  OCH3) and decreases drastically in polar solvents. According to these results a reaction mechanism is outlined and discussed.
Contribution à l'étude de dérivés O‐β‐hydroxyéthylés de la quercétine. Identification des dérivés par spectrophotométrie UV
Authors: Courbat Pierre , Valenza André
Published: December 2004

Par spectrophotométrie UV. on établit les structures de 8 dérivés O‐hydroxyéthylés de la quercétine obtenus par trois voies: (a) l'hydrolyse acide de dérivés identifiés O‐hydroxyéthylés de la rutine conduit aux monoéther‐4′, di‐éther‐7, 4′, tri‐éther‐7, 3′, 4′ et tétra‐éther 5, 7, 3′, 4′; (b) l'hydroxyéthylation soit modérée de la quercétine ou du tri‐éther‐7, 3′, 4′, qui conduit au tétra‐éther‐3, 7, 3′, 4′, soit totale de la queréctine, du tri éther‐7, 3′, 4′ ou de l'un ou l'autre des tétra‐éthers‐5, 7, 3′, 4′ ou‐3, 7, 3′, 4′, qui conduit au penta‐éther‐3, 5, 7, 3′, 4′; (c) enfin, la déshydroxyéthylation partielle de l'un ou I'autre des tri‐, tétra‐ ou penta‐éthers au moyen du chlorure d'aluminium anhydre dans le nitrobenzène engendre le di‐éther‐7, 3′ et le mono‐éther‐7.
The Total Synthesis of (±) β‐Acorenol. Preliminary communication
Authors: Oppolzer Wolfgang
Published: December 2004

Die erste Totalsynthese des Spiro‐sesquiterpenes β‐Acorenol, ausgehend vom bekannten Cyclohex‐1‐enylessigsäureäthylester, wird beschrieben. Die Schlüsselstufe 2 → 3 + 4 verläuft über eine thermische intramolekulare En‐Reaktion.
Synthesis of Optically Active, Ring‐Substituted N‐Benzyloxycarbonylphenylalanines via 2‐Benzyloxycarbonylamino‐2‐arylalkylmalonates
Authors: Bosshard Hans Rudolf , Berger Arieh
Published: December 2004

Diethyl or dimethyl benzyloxycarbonylaminomalonate was reacted with ring substituted benzyl halides and the resulting arylalkyl derivatives (3 to 6) half‐saponified to the DL‐monoacid‐monoesters (7 to 10). Decarboxylation by refluxing in dioxane afforded the N‐benzyl oxycarbonyl‐DL‐amino acid esters (11 to 14), which were resolved into their optical antipodes by enzymic hydrolysis of the ester group with Subtilisin, type Carlsberg. Enzymic hydrolysis led to the N‐benzyloxycarbonyl‐L‐amino acids (15 to 18) and to the corresponding D‐amino acid esters. The latter were converted to the N‐benzyloxycarbonyl‐D‐amino acids (19 and 20) by alkaline hydrolysis of the ester groups. These derivatives could be used directly for further peptide synthesis. The following compounds were prepared: N‐benzyloxycarbonyl derivatives of p‐methyl‐L‐phenylalanine (15), p‐methyl‐D‐phenylalanine (19), p‐fluoro‐L‐phenylalanine (16), m‐fluoro‐L‐phenylalanine (17), m‐fluoro‐D‐phenylalanine (20) and penta‐fluoro‐L‐phenylalanine (18). The free amino acids were obtained by removal of the benzyloxycarbonyl group with HBr in acetic acid.
Studien in der Flavin‐Reihe. XIX. Mitteilung. Anomale Reduktion des Flavinkerns: Pteridine aus (Iso)alloxazinen
Authors: Heizmann C. , Hemmerich P. , Mengel R. , Pfleiderer W.
Published: December 2004

The catalytic hydrogenation of isoalloxazines in aqueous solutions proceeds non stoichiometrically.

This is explained by a reaction side path, which is competitive with the normal reversible 1,5‐dihydrogenation and leads to the irreversible reduction of the ‘o‐xyloquinoid’ (rather than benzenoid) subnucleus in the (iso)alloxazine system. In trifluoroacetic acid, this irreversible side reaction is found to be complete within several hours, while 8 H‐equivalents are absorbed per flavin molecule. The products are shown to be cyclohexano‐[g]‐pteridine‐2,4‐diones in the normal 5,6,7,8‐tetrahydro state, which are oxidized to yield, subsequently, 7,8‐dihydro‐ and ‘fully oxidized’ pteridines (= 6,7,8,9‐tetrahydrofavins).

The spectral characteristics, tautomeric structures and pK‐values are discussed in context with recent data on 6,7,8‐trialkylpteridine‐2,4‐diones [3].
Photochemische Reaktionen. 74. Mitteilung. Notiz zur Photoreaktivität ausgewählter ungesättigter Ketoalkohole der Jononreihe
Authors: von Wartburg Beat R. , Wolf Hans R. , Jeger Oskar
Published: December 2004

UV.‐irradiation (λ = 254 nm) of the hydroxy‐enones 3 and 6 in acetonitrile results in the cyclization to the unstable isomeric allylic alcohols 4 and 7, which dehydrate easily to the isolated unsaturated ether 5 and 8. The racemic γ,δ‐dihydroxy‐enone 9 upon irradiation under the same conditions gives rise to the exclusive formation of the furane‐compound 11.
Photoinduzierte Cycloadditionen von 3‐Benzyl‐2H‐azirin
Authors: Orahovats Alexander , Jackson Barry , Heimgartner Heinz , Schmid Hans
Published: December 2004

Irradiation of 2‐azido‐3‐phenyl‐propene (5) in pentane or benzene solution with a high pressure lamp (pyrex filter) yields 3‐benzyl‐2H‐azirin (6), which on further irradiation behind quartz or vycor in the presence of trifluoroacetic acid methylester or carbon dioxide yields 4‐benzyl‐5‐methoxy‐5‐trifluoromethyl‐3‐oxazolin (8) and 4‐benzyl‐3‐oxazolin‐5‐one (9), respectively (scheme 2). A small amount of 3‐phenylacetonitrile is also formed.
The Enol of Acetone during Photochemical Reactions of 3‐Hydroxy‐3‐methyl‐2‐butanone and of Acetone
Authors: Laroff Gary P. , Fischer H.
Published: December 2004

The enol of acetone, formed by disproportionation reactions of 1‐hydroxy‐1‐methylethyl radicals, is detected by NMR, spectroscopy during photoreactions of 3‐hydroxy‐3‐methyl‐2‐butanone in acetonitrile and of acetone in 2‐propanol and slowly tautomerizes to acetone. The photolysis of 3‐hydroxy‐3‐methyl‐2‐butanone is shown to proceed via Type I cleavage, predominantly from an excited triplet state.
Zur Kenntnis der 4‐Thioglucose
Authors: Vegh L. , Hardegger E.
Published: December 2004

Die aus 1,6;3,4‐Dianhydro‐D‐galaktopyranose (2) erstmals hergestellte 4‐Thio‐D‐glucose, welche fast ausschliesslich in der Thiophanoseform 19 vorliegt, ist hygroskopisch, oxydationsempfindlich und zersetzlich. Die wässerigen und äthanolischen Lösungen der 4‐Thio‐D‐glucose sind besser haltbar, ebenso das in der Pyranoseform vorliegende Natriummercaptid 15.
Cycloadditionen von Heterocumulenen an CN‐Bindungssysteme. 2. Mitteilung. Perhydro‐s‐triazindione und cyclische Aminimide aus N,N‐Dimethyl‐N′‐dimethylamino‐formamidin und Isocyanaten
Authors: Seckinger Karl
Published: December 2004

The addition of the arylisocyanates 12a–12p to N,N‐dimethyl‐N′‐dimethylaminoformamidine (7) leads to the cyclic aminimides 14a–14p. Methyl isocyanate and phenyl isotiocyanate react with 7 in an analogous manner and yield the compounds 24 resp. 30. The arylisocyanates 12q–12v, however, which contain electron‐withdrawing groups in the ortho‐ and/or meta‐position, undergo 1,4‐dipolar cycloadditions and react with the amidine 7 to furnish the perhydro‐s‐triazine‐diones 22a–22ff. The mechanism of these reactions is discussed.
Die Struktur des sogenannten Anhydro‐N‐oxy‐nornarceins. Vorläufige Mitteilung
Authors: Klötzer W. , Oberhänsli W. E.
Published: December 2004

Aus α‐Narcotin‐N‐oxid 1 erhält man durch Isomerisierung das sogenannte Anhydro‐N‐oxy‐nornarcein. Die bisherigen Strukturannahmen A [2] und B [3] werden zur Achtring‐Formel 2 korrigiert. ß‐Hydrastin‐N‐oxid 1a liefert bei der Isomerisierung ein Gemisch aus zwei Verbindungen mit der Bruttoformel eines Anhydro‐N‐oxy‐norhydrasteins, von denen eine ebenfalls die Achtring‐Struktur 2a aufweist, die zweite jedoch das unter Ringöffnung entstandene Enollacton 3 darstellt.
The MO‐theoretical Description of Optical Properties in Polymers. Selection rules due to cyclic symmetry
Authors: Wagnière G. , Geiger R.
Published: December 2004

The possibility is considered of applying routine semiempirical SCF‐MO‐CI procedures to the optical properties of polymers, such as polyamino acids, for instance. The polymer is assumed to be of intermediate length, namely, long enough that cyclic boundary conditions may be applied, but definitely shorter than the wavelength of incident light. Selection rules such as those which were derived by Moffitt in the frame of the exciton model are here translated into the MO picture. In the case of a helix the transitions polarized perpendicular to the axis of the helix are governed by clear‐cut selection rules only if the number of repeating units N strictly corresponds to an integral multiple of a translational identity period. Questions concerning the tractability of the configuration interaction calculation are discussed.
C(8) Epimeric 8‐Hydroxy‐erythromycins‐A
Authors: Tadanier Jack , Kurath Paul , Martin Jerry R. , McAlpine James B. , Egan Richard S. , Goldstein Alma W. , Mueller Sandra L. , Dunnigan Daniel A.
Published: December 2004

Die sorgfältig kontrollierten Persäure‐Oxydationen von 8,9‐Anhydro‐erythromycin‐A‐6,9‐hemiacetal‐N‐oxid und 8,9‐Anhydro‐erythromycin‐A‐6,9‐hemiacetal liefern nach der katalytischen Reduktion der N‐Oxidgruppe direkt und stereoselektiv das (8S)‐8‐Hydroxy‐erythromycin‐A nebst einer geringen Menge des 8‐epi‐(8 R)‐8‐Hydroxy‐erythromycins‐A. Die Resultate der Persäure‐Oxydationen der 8,9‐Anhydro‐erythromycin‐A‐ und B‐hemiacetale werden verglichen.
Die Isolierung weiterer Alkaloide aus Pleiocarba talbotii WERNHAM. 150. Mitteilung über Alkaloide
Authors: Pinar Mariano , Hesse Manfred , Schmid Hans
Published: December 2004

From the leaves of the Apocynaceae Pleiocarpa talbotii WERNHAM three new indole alkaloids were isolated and identified as 3,4,5,6‐tetradehydrotalbotine (2), 5,6‐dehydrotalbotine (3) and deformyl talbotinic acid methylester (4). From the stem bark of the same plant normacusine B (tombozine) was isolated.
Nachweis von π → σ‐Umlagerungen bei Ligandenverdrängungsreaktionen von π‐Allyl‐π‐cyclopentadienyl‐Palladiumkomplexen
Authors: Parker Graham , Werner Helmut
Published: December 2004

It has been proved by NMR. measurements at low temperatures that the ligand displacement reactions of (π‐all)Pd(π‐C5H5) and Lewis bases L yielding PdL4 proceed by a π → σ rearrangement of the allylic group as the primary step. The organic reaction product is the 1‐isomer of the corresponding allylcyclopentadiene but in the reactions of (π‐1,1,2‐Me3C3H2)Pd(π‐C5H5) with L besides the isomeric allylcyclopentadienes also 2,3‐dimethylbutadiene and cyclopentadiene are formed. The reaction mechanism will be discussed.
Isolierung und Strukturaufklärung von 11‐Desacetoxy‐wortmannin
Authors: Haefliger Walter , Hauser Daniel
Published: December 2004

The structure of 11‐desacetoxy‐wortmannin (3), a new antiinflammatory metabolite of the fungus Penicillium funiculosum THOM, has been elucidated by physico‐chemical methods and chemical correlation with wortmannin (1).
α‐Chlor‐nitrone VI: Ag+‐induzierte Reaktion mit Acetylen‐derivaten. Eine neue Bildungsweise von α,β‐ungesättigten Carbonylsystemen Über synthetische Methoden, 10. (vorläufige) Mitteilung
Authors: Shatzmiller Shimon , Eschenmoser Albert
Published: December 2004

α‐Chloro‐aldonitrones provide a novel synthetic pathway from acetylenes to αβ‐unsaturated enone systems.
Etude de la fragmentation des alkyl‐thiazoles en spectrographie de masse
Authors: Tabacchi Raffaele
Published: December 2004

The mass spectra of 27 mono‐, di‐ and trisubstituted alkyl‐thiazoles are reported and discussed. The predominant fragmentation is characterized by the loss of R2CN with formation of a thiiren‐ion and the β‐cleavage with respect to the cyclic double bonds.
Steroids and Sex Hormones. Part 250. Transformation of dehydroabietic acid into 14‐methyl‐steroids II. The synthesis of 3‐oxo‐17β‐acetoxy‐14α‐methyl‐δ4‐8α, 9β, 10α, 13α‐estrene. Preliminary communication
Authors: Wirthlin Toni , Wehrli Hansuli , Jeger Oskar
Published: December 2004

Zusammenfassung. Im Rahmen der vorliegenden Mitteilung berichten wir über den partial‐synthetischen Aufbau von 3‐Oxo‐17 β‐acetoxy‐14α‐methyl‐Δ4‐8α, 9β, 10α, 13α‐östren (12), dessen Struktur anschliessend mittels dreidimensionaler Röntgenanalyse [2] sichergestellt worden ist. Als Ausgangsmaterial der Synthese diente die tricyclische Verbindung 2, die, zusammen mit 3, von uns (s. vorhergehende Mitt. [1]), aus Dehydroabietinsäure (1) dargestellt worden ist.
Über die Struktur der makrocyclischen Spermidin‐Alkaloide Oncinotin, Neooncinotin und Isooncinotin. 151. Mitteilung über Alkaloide
Authors: Guggisberg A. , Badawi M. M. , Hesse M. , Schmid H.
Published: December 2004

Three spermidine alkaloids – oncinotine (1), neooncinotine (3), and isooncinotine (2) – have been isolated from the stem bark of Oncinotis nitida BENTH. (Scheme 1); 1 and 3 are so far an unseparable mixture. However, by treatment of this mixture with K‐t‐butoxide, neooncinotine is completely converted into isooncinotine, and oncinotine, the main alkaloid, is obtained in pure form.

The structural assigment of these alkaloids is based on chemical and spectral evidence. Thus oncinotine (1) has been degraded via 24 (Scheme 4) and 32 to the putrescine derivative 35 and the piperidine derivative 34 (Scheme 5). Similarly neooncinotine (3) and isooncinotine (2), have given 34 along with the 1, 3‐diaminopropane derivative 36 (Scheme 5). The major decomposition pathways of 24, 35 and 36 in the mass spectra are described in Schemes 8, 6 and 7 respectively. The absolute configuration of 1, 2 and 3 is derived by chiroptical correlations with (R)‐(−)‐N‐methylconiine (38).
The Reaction of some Carbonyl and Thiocarbonyl Compounds with Prenyl‐ and Crotyllithium in Tetrahydrofuran Solution
Authors: Rautenstrauch V.
Published: December 2004

Prenyllithium (3‐methylbut‐2‐enyl‐lithium) (1) and cis‐crotyllithium (Z‐but‐2‐enyl‐lithium) (2) in tetrahydrofuran solution, prepared according to the method of Eisch & Jacobs, react with carbonyl compounds to give the branched alcoholates with moderate to high selectivity, unless access to the carbonyl group is strongly hindered (see the Table). Adamantanethione (12) reacts with 1 to give the unbranched thiolate.
Ammonolysis of Nitroarginine and Nitroarginine‐Containing Peptides; Some Side Reactions
Authors: Künzi Hans , Manneberg Michael , Studer Rolf O.
Published: December 2004

Ammonolysis of nitroarginine‐containing peptides leads to the formation of ornithine‐containing side products. The structure of these side products has been deduced from model experiments. This side reaction can be avoided by using the NG‐tosyl or the NG‐dicarbobenzoxy protecting groups.
Vitamin D3 Metabolites II. Further Syntheses of 25‐Hydroxycholesterol
Authors: Narwid Thomas A. , Cooney Kevin E. , Uskoković Milan R.
Published: December 2004

Zwei weitere Synthesen von 25‐Hydroxycholesterin (10) ausgehend von Pregnenolon (1) bzw. O‐acetylpregnenolon (13) werden beschrieben. Dabei wird jedesmal auch das noch unbekannte 20(S)‐25‐Hydroxycholesterin (11) erhalten. Fernerhin wird ein Zusammenhang zwischen der chemischen Verschiebung der NMR.‐Signale der C(21)‐Methylgruppe und der Stereochemie am C(20) festgestellt.
Etude par spectrométrie de masse des O‐isopropylidène‐1,2‐thréo‐ et ‐érythro‐furannoses et des quatre désoxy‐5‐O‐isopropylidène‐1,2‐pentofurannoses
Authors: Buchs Armand , Glangetas Alain , Tronchet Jean M. J.
Published: December 2004

The mass spectra of the O‐isopropylidene derivatives of threo‐ and erythro‐furanose and those of the four C(4) methylated stereoisomers have been studied. Fragmentation modes based upon deuterium labelling, metastable peaks and high‐resolution measurements are proposed. Each stereoisomer can be characterized by its low‐resolution mass spectrum.
Action du chlorure de nitrosyle sur le trichloréthylène et sur le tétrachloréthylène
Authors: Calvez Yves , Tuaillon Jacques , Perrot Roger
Published: December 2004

Nitrosyl chloride is only chlorinating in darkness and above 100°. In the sun light and at room temperature it reacts as a chlorinating, nitrosating, nitrating and oxidizing agent. With trichlorethylene in fact pentachlorethane 1,1,1,2‐tetrachloro‐2‐nitrosoethane, 1,1,1,2‐tetrachloro‐2‐nitroethane, dichloracetic acid and a compound of empirical formula C4H2Cl5NO2 are obtained. Tetrachloroethylene carried to hexachlorethane, pentachloronitrosoethane and tetrachloro‐2‐(pentachlorethyl)‐1,2‐oxazetidine.

Introduced nitrosyl chloride provided nitrogen monoxide prouved by gaz chromatography. This monoxide reacted afterwards to give nitrogen which is the single nitrogenous gazeous compound. Carbondioxide is a minor component of the gaz.
Azidiniumsalze. 12. Mitteilung [1]. Das ambidente reaktive Verhalten des 2‐Azido‐3‐äthyl‐benzthiazolium‐Ions gegenüber Nucleophilen
Authors: Balli Heinz
Published: December 2004

Die Reaktivität von «harten» und «weichen» Nucleophilen (Hydroxid, Methoxid, Dimethylamin, 2‐Imino‐3‐äthyl‐benzthiazolin, Triphenylphosphin, Carbanionen, Azid, Cyanid, Arylsulfinat, 3‐Äthyl‐benzthiazolin‐2‐yliden, 3‐Methyl‐benzthiazolinon‐(2)‐hydrazon) gegenüber dem ambidenten elektrophilen 2‐Azido‐3‐äthyl‐benzthiazolium‐Ion wird untersucht. Das reaktive Verhalten lässt sich mit Hilfe des HSAB‐Konzepts von Pearson deuten.
Neue β‐Lactam‐Antibiotika. Über Derivate der 3‐Hydroxy‐7‐amino‐ceph‐3‐em‐4‐carbonsäure. Modifikationen von Antibiotika, 10. Mitteilung [1]
Authors: Scartazzini Riccardo , Bickel Hans
Published: December 2004

3‐Hydroxy‐ceph‐3‐em‐esters 5 a–c, versatile intermediates for the preparation of new β‐lactam antibiotics, were obtained by ozonolysis of the corresponding 3‐methylidene‐esters 3 a–c. Reduction and elimination gave the 3‐unsubstituted ester 13; derivatives 16 a–c and 20–22 resulted from O‐alkylation. The 3‐methoxy‐esters 16 a–c were converted into the corresponding acids 23 a–d. Several other transformations of the β‐ketoester system are described.
Recherches dans la série des cyclitols XLV. Action des diazoalcanes sur la pentahydroxy‐2,4,6/3,5‐cyclohexanone et sur son dérivé penta‐O‐acétylé. I. Etude des spiro‐époxydes
Authors: Giddey André , Cocu Florea G. , Pochelon Béatrice , Posternak Théodore
Published: December 2004

On treatment with diazomethane, 2,4,6/3,5‐penta‐acetoxy‐cyclohexanone(penta‐O‐acetyl‐myo‐inosose‐2 or ‐scyllo‐inosose) gave only a spiroepoxide. In contrast, replacement of diazomethane by higher diazoalkanes furnished a mixture of alkylspiroepoxides and of ring expansion products (cycloheptanone derivatives). The configuration and the reactions of the spiro‐epoxides have been studied.
Recherches dans la série des cyclitols XLVI. Actions de diazoalcanes sur la pentahydroxy‐2,4,6/3,5‐cyclohexanone et sur son dérivé penta‐O‐acétylé II. Etude de pentahydroxy‐alkyl‐C‐cycloheptanones
Authors: Cocu Florea G. , Pochelon Béatrice , Giddey André , Posternak Théodore
Published: December 2004

On treatment with higher diazoalkanes, 2,4,6/3,5‐penta‐acetoxy‐cyclohexanone (penta‐O‐acetyl‐myo‐inosose‐2 or ‐scyllo‐inosose) afforded by ring expansion all‐trans‐penta‐acetoxy‐C‐alkyl‐cycloheptanones, which by deacylation were converted to hemiacetals. The reactions with diazoalkanes of the penta‐acetoxy‐inosose in the presence of aluminium chloride and of the free inosose in water solution have also been studied. The structure, the configuration, and, in some cases, the conformation of the new compounds have been established and some of their reactions have been investigated. The mechanisms of formation of the ring expansion products and of the concomitant spiro‐epoxides have been discussed.
Zur Herstellung von 1,2,3‐Tricarbonylverbindungen aus 1,3‐Dicarbonylverbindungen. 27. Mitteilung über Reduktone und Tricarbonylverbindungen [1]
Authors: Dayer Francis , Dao Huu Lê , Gold Hellmut , Rodé‐Gowal Heike , Dahn Hans
Published: December 2004

The synthesis of 22 substituted tricarbonyl compounds is reported. They were obtained either by oxidation of β‐dicarbonyl compounds with SeO2 or nitrous oxides or by oxidation of the α‐bromo‐β‐dicarbonyl compounds with DMSO. The procedures using SeO2 or DMSO are more rapid and give in general better yields than other methods described in the literature.
Synthese und Basizität 4‐substituierter Chinuclidine. Chinuclidinreihe 12. Mitteilung
Authors: Ceppi Eros , Grob Cyril A.
Published: December 2004

The preparation of a number of 4‐substituted quinuclidines and the PKa values of their hydroperchlorates in water are reported.
Synthese und Basizität 4‐heterosubstituierter. Chinuclidine Chinuclidinreihe, 13. Mitteilung
Authors: Eckhardt Wolfgang , Grob Cyril A.
Published: December 2004

The preparation of several 4‐heterosubstituted quinuclidines and the pKa values of their hydroperchlorates in water are reported.
Recherches sur la biochimie des champignons inférieurs VIII. Synthèse chimique de pigments diquinoniques
Authors: Kalamar Julius , Steiner Eric , Charollais Etienne , Posternak Théodore
Published: December 2004

New simplified syntheses of two natural p‐diquinonic pigments, phoenicine and oosporeine, have been described. By similar procedures, the syntheses of two other related diquinones have been carried out: 3,3′,6,6′‐tetrahydroxy‐biphenyl‐di‐p,p′‐quinone and 3,3′,6,6′‐tetrahydroxy‐4‐methyl‐biphenyl‐di‐p,p′‐quinone. The latter structure had been assigned to pyxiferine, which had been reported to be contained in the lichen Pyxine coccifera.
The Radical Anions of Heptalene and 1, 7‐Methano‐[12]annulene
Authors: Müllen Klaus
Published: December 2004

The radical anions of heptalene and of 1, 7‐methano‐[12]annulene are generated by metal reduction and characterized by means of their ESR‐spectra. Whereas the neutral hydrocarbons are π‐bond localized their corresponding radical anions turn out to be π‐bond delocalized. This could be deduced from an interpretation of the different hyperfine splittings using a simple MO‐model.
3‐Oxawurtzitane (3‐Oxatetracyclo[5.3.1.12,604,9]dodecane)
Authors: Klaus Rolf Otto , Tobler Hans , Ganter Camille
Published: December 2004

A synthesis of 3‐oxawurtzitane (3‐oxatetracyclo[5.3.1.12,604,9]dodecane) (8) is described.
Photoinduzierte Cycloadditionen von aliphatischen 2H‐Azirinen. 37. Mitteilung über Photoreaktionen
Authors: Orahovats Alexander , Heimgartner Heinz , Schmid Hans , Heinzelmann Willy
Published: December 2004

The purely aliphatic 2,3‐dipropyl‐2H‐azirine (1) reacts on irradiation with a mercury high‐pressure lamp through a Vycor filter with methyl trifluoroacetate or acetone to form 3‐oxazolines 3a, b (65%) resp. 4 (14%) (Scheme 1). 9‐Azabicyclo[6.1.0]non‐1(9)‐ene (5) on irradiation in the presence of the dipolarophiles methyl trifluoroacetate, methyl difluoroacetate, 1,1,1‐trifluoro‐propanone and acetone behaves in a similar way, whereby the corresponding bicyclic 3‐oxazolines 7–10 result in yields of 60–20% (Scheme 2).

By analogy with the photochemical behaviour of 3‐aryl‐2H‐azirines it is assumed that nitrile‐ylides 2 resp. 6 represent intermediates. In fact irradiation of 2,3‐dipropyl‐2H‐azirine (1, λmax 239 nm, ϵ 240) at −196° with light of wavelength 245 nm in a hydrocarbonglass gives rise to a pronounced maximum at 280 nm, for which an ϵ of ⩾ 15000 can be estimated. The quantum yield for the formation of nitrile‐methylide 2 is 0,8. Irradiation of the dipole 2 at −196° or warming to −150° causes the maximum at 280 nm to disappear.
Studies on Heterocyclic Colouring Matters Part II: Δ2,2′ ‐Bi (2H‐1, 4‐benzothiazines)
Authors: Kaul B. L.
Published: December 2004

A novel one‐step ‘Inverse Indigo Synthesis’ of the Δ2,2′‐bi(3,4‐dihydro‐3‐oxo‐2H‐1, 4‐benzothiazine) chromophore is described. Structure, substitution reactions, mechanism of formation, colour and other relevant properties of this system have been investigated in relation to known thioindigos. A synthesis of the basic skeleton of one of the ‘Trichosiderins’, the colouring matters of human red hair, is reported.
Photochemical Reactions. 80th Communication [1]. Preliminary report on the photolysis of (E) – Dehydro‐β‐ionone‐epoxide
Authors: Ehrenfreund Josef , Gaoni Yehiel , Jeger Oskar
Published: December 2004

Irradiation of a pentane solution of (E)‐dehydro‐β‐ionone‐epoxide (1) with light from a medium pressure mercury lamp using acetone as filter led to formation of the isomers 2, 3, 4 and 5 by novel photochemical processes.
Die Benzoin‐Phenol‐Synthese
Authors: Egli Christian , Helali Salah Eldin , Hardegger Emil
Published: December 2004

α‐Ketole vom Benzointyp und Methylvinylketon bzw. Benzylidenaceton geben unter Michael‐Addition, Aldolkondensation und Wasserabspaltung in hoher Ausbeute 3,4‐disubstituierte Phenole, bzw. 3,4‐disubstituierte 5‐Phenyl‐phenole, die auf anderen Wegen nur schwierig zugänglich sein dürften. Mit Propionoin und Methylvinylketon nimmt die Reaktion einen anderen Verlauf und führt einheitlich zu 2,3‐6‐Äthyldimethylphenol.
The Interaction of Argon with Sulfur Surfaces. Experimental and calculated variations of the adsorption potential with surface coverage
Authors: Stoeckli‐Evans Helen , Stoeckli Fritz
Published: December 2004

The adsorption potentials of argon on the (111), (001) and (110) planes of rhombic sulfur have been calculated for a total of 818 sites, using an intermolecular potential of the Lennard‐Jones (6:12) type with the Kirkwood‐Müller expression. Direct summation over the nearest 100–150 atoms of the solid was used. There is a good agreement between the experimental and the calculated values of the adsorption potential, as a function of the surface coverage.
Detection of 9‐methoxy substitution in tetrahydroprotoberberine alkaloids by mass spectrometry
Authors: Richter Wilhelm J. , Brochmann‐Hanssen Einar
Published: December 2004

9‐Methoxytetrahydroprotoberberines are found to exhibit pronounced (MOCH3)+ ions in their mass spectra as opposed to isomers or homologs lacking such substitution, yet carrying methoxyl substituents at other sites. Locating such substituents originally present, or produced from 9‐hydroxy groups by treatment with diazomethane, allows to differentiate 9, 10‐ from 10, 11‐oxygenation patterns in ring D, and thus to secure an important step in the structure elucidation of unknown alkaloids of this class.
Studies of Organometallic Compounds XVI. The Crystal Structure of Di‐μ‐ethoxy‐bis(dibenzylethoxy‐titanium(IV))
Authors: Stoeckli‐Evans Helen
Published: December 2004

The crystal structure of di‐μ‐ethoxy‐bis(dibenzylethoxy‐titanium(IV)), [(EtO)2Ti‐(CH2Ph)2]2, has been determined from analysis of photographic X‐ray data. The crystal system is monoclinic, a = 7.93(2), b = 15.99(2), c = 13.40(2) Å, β = 92.7(3)°, space group P21/c. The molecule is a dimer situated about a crystallographic center of symmetry. The two Ti atoms are joined by oxygen bridges. Each Ti atom is penta‐coordinated in the form of a distorted trigonal bipyramid.
Improved Synthesis of O‐Phosphohomoserine
Authors: Schnyder Jörg , Rottenberg Max
Published: December 2004

O‐Phosphohomoserine (PHS) was prepared in an overall yield of 49% by treatment of N‐benzyloxycarbonyl‐homoserine p‐nitrobenzyl ester with diphenylphosphoryl chloride in pyridine, followed by catalytic hydrogenolysis. Both L‐ and D, L‐phosphohomoserine were found to be 100% hydrolyzed by alcaline phosphatase from E. coli.
Eine chiral ökonomische Totalsynthese von natürlichen und unnatürlichen Prostaglandinen
Authors: Fischli Albert , Klaus Michael , Mayer Hans , Schönholzer Peter , Rüegg Rudolf
Published: December 2004

Using a meso‐compound which is asymmetrically substituted with a chiral moiety as an intermediate, prostaglandins have been synthesized. Since the undesired enantiomer is readily recycled, this approach leads to a synthesis with high chiral efficiency. In addition it is possible to prepare both enantiomeric configurations of prostaglandins by simply altering the sequence of reactions. This concept should be generally useful in the synthesis of optically active molecules.
The Crystal and Molecular Structure of rac‐15‐cyano‐1,2,2,7,7,12,12‐heptamethyl corrin hydrochloride, metal free corrin
Authors: Edmond Eric D. , Crowfoot‐Hodgkin Dorothy
Published: December 2004

The crystal structure of a metal free corrin hydrochloride synthesised by Eschenmoser & Fischli has been found by X‐ray analysis. The crystals are monoclinic and contain ethanol of crystallisation; a = 10.84 Å, b = 12.04 Å, c = 26.04 Å, γ = 120.4 in space group P21/a. The structure was determined by direct methods and refined to R = 0.076 for 3252 statistically significant reflections with θ < 70° (Cu Kα). The A ring is found to be markedly displaced from the mean plane of the other three rings; hydrogen atoms are observed in difference electron density maps to be bonded to N21 and N23 of the nucleus. Details of the shape and dimensions of the nucleus are discussed.
Neue Synthesen von Pyrazolo[1,5‐a]‐s‐triazinen
Authors: Vogel Arnold , Troxler Franz
Published: December 2004

Two new syntheses of pyrazolo[1,5‐a]‐s‐triazines are reported: (a) Addition of acetyl isocyanate to 5‐amino‐3‐methyl‐pyrazole followed by hydrolysis yields N‐(3‐methyl‐5‐pyrazolyl)‐urea (15), which on cyclisation with triethyl orthoacetate gives 2‐hydroxy‐4,7‐dimethylpyrazolo[1, 5‐a]‐s‐triazine (16). (b) Condensation of aminoguanidine with β‐oxo‐nitriles affords 1‐amidino‐5‐aminopyrazoles 18. These are cyclised to pyrazolo[1,5‐a]‐s‐triazines 19‐‐21 by reaction with orthoesters, acetic‐formic anhydride, phenylisocyanide dichloride, dimethyl oxalate, N, N′‐carbonyldiimidazole, and N, N′‐thiocarbonyldiimidazole. The 4‐amino group in 19 is converted by standard procedures to OH, SH, SCH3, Cl and NRR′. Reaction of pyrazolo[1,5‐a]‐s‐triazines 30 with electrophiles leads to compounds substituted at position 8, e.g. 32a‐‐e.
Considerations on the Interpretation of Mass Spectra via Learning Machines
Authors: Kent Phillippe , Gäumann Tino
Published: December 2004

The application of learning machine techniques to the interpretation of mass spectra is investigated. An attempt to improve the characteristic ratio of the number of training points to the number of adjustable parameters is made by the use of reduced spectra. The ensuing results are corrected for the unequal representation of the different substances in the data bank. Reasonable performance is obtained for spectra of simple (monofunctional) substances, but predictive abilities are poor for more complicated substances.
Die photochemische Tautomerisation eines cyclischen Amidins
Authors: Pfoertner Karl‐Heinz
Published: December 2004

The cyclic amidine group of the 8‐amino‐2,3,5,5a‐tetrahydro‐5,8a‐propeno‐6H,11H‐pyrrolo[3,4‐g]‐1‐pyrindine (2) undergoes photochemical tautomerism. In this reaction the dihydropyridine group of a second molecule of 2 acts as a sensitizer.
Die photochemische Reduktion von 4,6‐Dimethyl‐2‐pyrimidinol
Authors: Pfoertner Karl‐Heinz
Published: December 2004

π,π*‐Excitation of 4,6‐dimethyl‐2‐pyrimidinol in methanol leads to an addition product 5 whereas in 2‐propanol a dihydrodimer 3 is formed. By acid catalysis the dihydrodimer gives the 5, 9‐methano‐2H‐pyrimido[5,6‐e] [1,3]diazepine‐2,7(1H)‐dione 7 which with stronger acids rearranges to the 2H‐cyclopentapyrimidin‐2‐one 8. Nitrous acid reacts with the dihydrodimer yielding the dioxime of 2‐hydroxy‐4,6‐pyrimidinedicarbaldehyde.
Selektive Abspaltung säurelabiler Aminoschutzgruppen von Peptiden in Trifluoräthanol
Authors: Riniker Bernhard , Kamber Bruno , Sieber Peter
Published: December 2004

In building up large polypeptides, it has become the established practice to use acide‐labile protecting groups of the t‐butyl type. Up to now, only one step of selectivity under acidic conditions has been used, consisting in the cleavage of Trt, Bpoc or Ppoc from N(α) without attacking the t‐butyl protecting groups. We have found that the use of 90% trifluoroethanol as solvent permits the selective cleavage of Trt in the presence of Bpoc or Ppoc under controlled acidolytic conditions. This additional selectivity‐step may be utilized when two‐chained polypeptides are to be constructed.

The procedure consists in acidolytic cleavage with hydrochloric acid at a constant potential as measured by the glass electrode (pH‐stat). The automatic protonation of the freshly deprotected amino groups permits the evaluation of kinetic and quantitative data of the cleavage reaction. The selectivity ratios and cleavage conditions of Trt, Bpoc and Ppoc in N(α) are demonstrated here by reference to a series of model dipeptides. The successful application of this technique in the total synthesis of human insulin, a polypeptide with two peptida chains, has recently been described [8].
Die Diels‐Alder Reaktion von Furan und 2‐Methylfuran mit Acrylnitril
Authors: Kienzle Frank
Published: December 2004

Diels‐Alder reaction between furan or 2‐methylfuran and acrylonitrile furnished the expected adducts in good yields. The ratio of the various products was determined.
Studien über die Thorpe‐Ziegler‐Reaktion Eine neue Synthese des Pyrimidinteils von Thiamin
Authors: Edenhofer Albrecht , Spiegelberg Hans , Oberhänsli Willi E.
Published: December 2004

Thorpe‐Ziegler cyclization of N′‐cyano‐N‐(2‐cyanoethyl)‐acetamidine (5a) yields 4‐amino‐2‐methyl‐1,6‐dihydro‐5‐pyrimidinecarbonitrile (8a). The acetamidine 5a is accessible either from the N‐cyanoimidate 1 and β‐aminopropionitrile (3a) or the N‐cyanoamidine 2 and acrylonitrile (4). The dihydropyrimidine 8a is easily converted to 4‐amino‐2‐methyl‐5‐pyrimidine‐carbonitrile (13) by dehydrogenation or to 4‐amino‐5‐aminomethyl‐2‐methylpyrimidine (15) by hydrogenation‐dehydrogenation. Both products are important intermediates in the synthesis of thiamine.
Static and Dynamic Distortions in Five‐Coordinate Complexes of cobalt(II) and rhodium(I)
Authors: Higginson B. R. , McAuliffe C. A. , Venanzi L. M.
Published: December 2004

Five‐coordinate complexes have been prepared, of the general formulae [CoX(L'L3)]+ and [RhX(L'L3)], where X = halogen and L'L3 = a quadridentate tripod‐like ligand containing various Group V donor atom sets. The electronic spectra and magnetism of the cobalt(II) series can be interpreted on the basis of a low‐spin d7‐ion in a trigonal bipyramidal environment distorted by a static Jahn‐Teller effect. Electronic spectral data for the trigonal bipyramidal rhodium(I) series show that the low‐energy 1A → 1E ligand field transition is split at room temperature, but that the splitting collapses on reducing the temperature. This behaviour has been attributed to the operation of a dynamic Jahn‐Teller effect.
Synthesis of 4‐Oxo‐1,2,3,4‐tetrahydropyridine (2,3‐Dihydro‐4(1H)pyridinone)
Authors: Haider Akhtar , Cornuz Georges , Wyler Hugo
Published: December 2004

N‐Ethoxycarbonyl‐4‐pyridone is reduced to N‐ethoxycarbonyl‐4‐oxo‐1, 2, 3, 4‐tetrahydropyridine by sodium borohydride in t‐butyl alcohol containing ethyl chloroformate. Saponification of the product leads to 4‐Oxo‐1, 2, 3, 4‐tetrahydropyridine.
Kinetik und stereochemischer Verlauf der thermischen Umlagerung der vier stereoisomeren Propenyl‐(but‐2′‐enyl)‐äther
Authors: Vittorelli Piero , Hansen Hans‐Jürgen , Schmid Hans
Published: December 2004

The gas‐phase rearrangement of (1Z, 2′E)‐, (1Z, 2′Z)‐, (1E, 2′E)‐, and (1E, 2′Z)‐ propenyl but‐2′‐enyl ether (Z, E)‐, (Z, Z)‐, (E, E)‐, and (E, Z)‐1) into erythro‐ and threo‐2, 3‐dimethyl‐pent‐4‐en‐al (erythro‐ and threo‐2) was investigated over a temperature range from 142,5° to 190,0° at 20–35 Torr (for kinetic data and activation parameters see table 2). All four stereoisomeric ethers 1 rearrange preferentially via a chair‐like transition state C into the aldehydes 2 (ΔΔG≠ (160°) = 2,5–2,7 kcal/mol for B – C (B = boat‐like transition state). The relative rates (krel) for (Z, Z)‐1, (Z, E)‐1, (E,Z)‐1, and (E,E)‐1 at 160° are 1,0, 2,9, 4,3 and 9,0 respectively (see table 5). Taking into account the relative enthalpies of the ethers 1 and the steric interaction in the C transition state of the ethers 1 (see table 6), krel values can be estimated. They are in good agreement with those observed (see table 5).
Notiz über eine regiospezifische Methode zur Herstellung von konjugierten Cyclohexadienen Über synthetische Methoden, 11. Mitteilung
Authors: Rüttimann August , Wick Alexander , Eschenmoser Albert
Published: December 2004

β,γ‐unsaturated δ‐hydroxy‐cyclohexene carboxylic acids undergo a smooth decarboxylative elimination when treated with DMF‐dineopentylacetal in an unpolar solvent. The reaction provides a method for the regiospecific preparation of 1,3‐cyclohexadiene derivatives under non‐isomerizing conditions, starting from easily accessible and structurally variable intermediates.