bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient Conversion of Esters to α‐Trimethylsilylketones. Preliminary communication
Authors: Demuth Martin 
Published: December 2004

AbstractSecondary and tertiary carboxylic methyl or ethyl esters (2a‐c) were converted with trimethylslylmethyllithium (3a‐c) in high yields. Under identical reaction conditions the primary esters 2d,e gave 3d, e in lower yields. Since the trimethylsilyl (TMS) group α to a ketone is known to undergo facile elimination under a variety of reaction conditions, the method also constitutes a highly versatile ester to methylketone sequence.
A Novel Entry to the Eremophilane and Valencane Sesquiterpenes via a Stereoselective Intramolecular Diels‐Alder Reaction. Preliminary communication
Authors: Näf Ferdinand , Decorzant René , Thommen Walter 
Published: December 2004

AbstractA general stereoselective entry to racemic eremophilane and valencane sesquiterpenes, via a common key intermediate and using an intramolecular Diels‐Alder reaction, is described.
Planarization of Tetracoordinate Carbon Atom. Synthesis of 13‐oxa‐14‐oxo‐pentacyclo [5.5.2.1.04,15010,15]pentadecane, a bridged ‘tetraquinacane’ preliminary communication
Authors: Keese Reinhart , Pfenninger Armin , Roesle Alex 
Published: December 2004

AbstractStructural aspects of planoid deformation of tetracoordinate carbon atom, particularly those in annulenes with central carbon atom are discussed. [12] Annulene 11 with central carbon atom is proposed as compound with strong planoid deformation around the internal carbon centre. The synthesis of a saturated precursor 15 is described.
The Reaction of Patchoulol with Lead Tetraacetate, a Regiospecific Fragmentation
Authors: Thomas Alan F. , Ozainne Michel 
Published: December 2004

AbstractPatchoulol (1) forms 2,2,6,8‐tetramethylbicyclo [5.3.1]undec‐7‐en‐3‐one (5) with lead tetraacetate. This ketone undergoes acid‐catalyzed cyclization to 2,6,6,10‐tetramethyltricyclo [5.3.1.01,5]undec‐9‐en‐5‐ol (10), and is reduced to 2 stereoisomeric alcohols with lithium aluminium hydride. One of these alcohols 8 is readily dehydrated with cyclization to 2,6,6,10‐tetramethyltricyclo [5.3.1.01,5]undec‐9‐ene (12) and a double bond isomer 13, longer treatment with acid resulting in a Wagner‐Meerwein rearrangement to a mixture of two 1,3,7,7‐tetramethyltricyclo [6.2.1.02,6]‐undecenes (19 and 20), isomeric with β‐patchoulene (23). The other alcohol 7 with p‐toluenesulfonic acid forms the cyclic ether, 1,3,7,7‐tetramethyl‐11‐oxatricyclo‐[4.4.1.12,8]dodecane (15).
Totalsynthese von natürlichem α‐Tocopherol 3. Mitteilung. Aufbau der Seitenkette mit (−)‐(S)‐2‐Methyl‐γ‐butyrolacton als zentralem Baustein
Authors: Zell Reinhard 
Published: December 2004

Total Synthesis of Natural α‐Tocopherol(−)‐(S)‐2‐Methyl‐γ‐butyrolactone (2) represents a versatile chiral C5‐synthon. It serves as key intermediate in one of the syntheses of certain isoprenoid derivatives such as (R)‐dihydrocitronellol, (3R, 7R)‐hexahydrofarnesol and vitamin E of natural configurations. Their syntheses are described in detail.
The Structure of the Alkaloid Peduncularine. Communication no. 172 on organic natural products
Authors: Ros Hans‐Peter , Kyburz Rolf , Preston Nigel W. , Gallagher Rex T. , Bick I. Ralph C. , Hesse Manfred 
Published: December 2004

AbstractThe revised structure 1 is put forward for peduncularine, the main alkaloid of Aristotelia peduncularis (Labill.) HOOK. F. (Elaeocarpaceae), on the basis of its spectroscopic properties and those of its degradation products, the Hofmann base 3 and the hydrogenation product 4. Structure 1 represents the relative configuration of the alkaloid.Peduncularine belongs to the class of indole alkaloids with a monoterpene unit as the aliphatic portion. To our knowledge it constitutes the first example in which an isopropyl group has become detached from the terpene unit and occurs as a substituent on nitrogen.
Studies on Radical Cations, III. The Type C Valence‐Isomeric System Quadricyclane Radical Cation/Norbornadiene Radical Cation
Authors: Haselbach Edwin , Bally Thomas , Lanyiova Zuzana , Baertschi Peter 
Published: December 2004

AbstractThe previously discussed principles involved in electrocyclic reactions of openshell ions are exemplified for a type C system, the radical cation couple quadricyclane+ (Q+)/norbornadiene+ (NBD+). Exhaustive calculations (MINDO/3) for the various states of the ions support the general predictions for such types of systems. The barrier of interconversion Q+ → NBD+ is estimated to be significantly lower than that for the corresponding neutrals. Experimental support to this prediction is obtained by γ‐irradiation of Q or NBD in an electron scavenging matrix. In both cases only NBD+ is observed, indicating that Q+ is not stable at 77 K. Previous observations and propositions referring to the system Q+/NBD+ are discussed in view of the present findings.
Synthesis of Xanthone‐O‐Glycosides. II.. Synthesis of 1‐O‐β‐glycosides
Authors: Chari V. Mohan , Klapfenberger Rosalinde , Wagner Hildebert , Hostettmann Kurt 
Published: December 2004

AbstractSeveral naturally occurring xanthone‐1‐O‐glycosides have been synthesized in order to study monoamine oxidase (MAO) inhibition structure‐activity relationships. The syntheses also confirmed the structures as 1‐β‐D‐glucosyloxy‐3‐hydroxy‐5‐methoxyxanthone (Canscora decussata SCHULT.), 1‐O‐β‐primeverosyl‐3, 7, 8‐trimethoxyxanthone (decussatin‐1‐O‐primeveroside, Gentiana verna L.) and 1‐O‐β‐primeverosyl‐3, 8‐dimethoxy‐7‐hydroxyxanthone (gentiacaulein‐1‐O‐β‐primeveroside, Gentiana verna L.).
Identification et synthèse de nouveaux depsides isolés de la mousse de chêne (Evernia Prunastri (L.) ACH.). 4e Communication
Authors: Nicollier Gilles , Rebetez Michel , Tabacchi Raffaele 
Published: December 2004

Identification and synthesis of new depsides isolated from oakmoss (Evernia Prunastri (L.) ACH.)Lecanoric acid 5 and 4 new depsides have been isolated from oakmoss (Evernia Prunastri (L.) ACH.) extracts by means of silicagel column chromatography. Various spectral methods including 13C‐NMR. were used in determining the structure of 4,2″‐O‐methylgyrophoric acid (1), lecanoric acid (5), 2′‐O‐methylevernic acid (2), 3′‐methylevernic acid (3) and methyl 3′‐methyllecanorate (4).
Dérivés diglycosyliques. Communication préliminaire
Authors: Tronchet Jean M. J. , Habashi Ford , Martin Olivier R. , Bonenfant Alain P. , Baehler Bruno , Zumwald Jean‐Bernard 
Published: December 2004

Diglycosyl Derivatives. Preliminary communicationNovel types of diglycosyl compounds, some of them bearing a resemblance to natural di‐ or tri‐saccharides are described: a diglycosyldiyne (1), a diglycosylthiophene (2), a diglycosylaziridine (3), a diglycosyldioxolane (4), as well as six C,N‐diglycosylnitrones, 9b–9f and 14. These C,N‐diglycosylnitrones, on treatment with an acetylenic Grignard reagent, led to the expected acetylenic diglycosyl‐hydroxylamine 11, whereas diglycosylisoxazolines (f. ex. 10) were obtained when these nitrones underwent 1,3‐dipolar cycloaddition to acetylenic compounds.
Additionsreaktionen von 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirin an Phenylisocyanat und Diphenylketen
Authors: Mukherjee‐Müller Gabriele , Heimgartner Heinz , Schmid Hans 
Published: December 2004

Addition Reaction of 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine with Phenylisocyanate and Diphenylketene3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine (1a) reacts with carbon disulfide and isothiocyanates with splitting of the azirine N(1), C(3)‐double bond to give dipolar, fivemembered heterocyclic 1:1 adducts. In some cases, these products can undergo secondary reactions to yield 1:2 and 1:3 adducts. In this paper it is shown that the reaction of 1a with phenylisocyanate also takes place by cleavage of the N(1), C(3)‐bond, whereas with diphenylketene N(1), C(2)‐splitting is observed.The reaction of 1a and phenylisocyanate in hexane at room temperature yields the 1:3 adduct 2 in addition to the trimeric isocyanate 3 (Scheme 1). A mechanism for the formation of 2 is given in Scheme 5. Hydrolysis experiments with the 1:3 adduct 2, yielding the hydantoins 4–6 and the ureas 7 and 8 (Schemes 3 and 5), show that the formation of this adduct via the intermediates d, e and f is a reversible reaction.The aminoazirines 1a and 1b undergo an addition reaction with diphenylketene to give the 3‐oxazolines 14 (Scheme 8), the structure of which has been established by spectral data and oxidative degradation of 14a to the 3‐oxazolin‐2‐one 15 (R1  R2  CH3, Scheme 9).
Beitrag zum Reaktionsmechanismus der Synthese von Seychellen [1]
Authors: Fráter György 
Published: December 2004

New Mechanistical Details Concerning the Synthesis of Seychellen [1]In the last step of our synthesis of Seychellen (2) [1], the solvolysis of 1, only one side‐product was formed, namely 3 (Scheme 1). Now the structure of 3 has been elucidated, mainly by spectroscopic studies of its derivatives 7 and 9 (Scheme 2). In order to differentiate between two different solvolytic pathways from 1 to 3 (see Scheme 1 and 3) d3‐1 was prepared. Solvolysis of d3‐1 proved the mechanism shown in Scheme 1. Solvolysis of 1 and of 2‐epi‐1, respectively, furnished the same product distribution, which makes a common intermediate a very probable. In both cases 10 is an intermediate, which is slowly converted into 2 and 3. 2‐epi‐1 was prepared from 1 (Scheme 5).Kinetic measurements with 1, d3‐1 and 2‐epi‐1 are also in agreement with the mechanism drawn in Scheme 4: k1(72°) = (5,2±0,5) · 10−5 sec−1, k1(H)/k1(D)(72°) = 1,4±0,15; k2(H)/k4(H) = 0,66 and k2(H)/k2(D) = 2,2 if k4(H) ≈ k4(D) is assumed.
Spiro‐β‐lactame durch [2+2]‐Cycloaddition von Ketenen an Iminolactone
Authors: Roth Martin 
Published: December 2004

Spiro‐β‐lactams from [2+2]‐Cycloaddition of Ketenes to IminolactonesIminolactones (‘Isoimides’) derived from maleic anhydride and amines are shown to react with various ketenes in a [2+2]‐cycloaddition mode. Either preformed ketenes or the combination acid chloride/tertiary amine can be used as reagent. The reaction products have been assigned the spiro‐β‐lactam structure. Unsubstituted ketene is inert under the reaction conditions. It is possible to synthesize the spiro‐β‐lactams in a one‐pot procedure, starting from a mixture of maleic anhydride/amine and excess dialkylketene.
Medium Effects on C,C‐Bond Cleavage in the Alcohol Oxidation with Chromic Acid
Authors: Müller Paul , Blanc Jacky 
Published: December 2004

AbstractThe C,C‐bond cleavage which occurs during chromic acid oxidation of t‐butylphenylmethanol (1) and 1,2‐diphenylethanol (2) to the extent of up to 67% is reduced to 3% for 1 and 13% for 2 when the reaction is run in acetone, and totally suppressed upon co‐oxidation of the alcohols 1 and 2 with oxalic acid. Similarly, the yield of 7‐norbornanone obtained from 7‐norbornanol (7) is raised in going from acetic acid (24%) to acetone (41%) and approaches 100% in the co‐oxidation. With the co‐oxidation 5‐endo‐bicyclo [2.1.1]hexanol (3) is converted to the corresponding ketone in 54% yield. Mechanistic implications of these results are discussed.
On the Misleading Interpretation of the Properties of the f‐Electron Elements
Authors: Fidelis Irena 
Published: December 2004

AbstractThe aim of the paper is to elucidate the problem of the regular changes in the properties of f‐elements represented by the double‐double effect. It is pointed out that because of the half‐filled shell and double‐double effects the f‐element properties cannot be plotted as a linear function of the L‐quantum number, as suggested by Sinha [1][2].
An Answer to the Article ‘On the Misleading Interpretation of the Properties of the f‐Electron Elements’
Authors: Sinha Shyama P. 
Published: December 2004

AbstractThe position of the ‘Inclined W theory’, i.e., the linear correlation of the properties (Pi) of the lanthanide and the actinide ions with their ground state total orbital angular quantum numbers (L), Pi = wiL + ki, where wi and ki are the slopes and intercepts of the least squares lines, is made clear. The position of gadolinium is ambivalent, and it can be a common point for the symmetric ‘Inclined W plots’ or it may either belong to the second or the third tetrad depending on the system investigated. The propionate and the isobutyrate systems are used to elucidate the ‘Inclined W concept’. The ‘Inclined W parameters’ for the solvent extraction of the lanthanides with PMBP ligand have been calculated.
Macrocycles by Olefination of Dialdehydes with 1,3‐Bis(dimethylphosphono)‐2‐propanone
Authors: Büchi George , Wüest Hans 
Published: December 2004

AbstractConjugated cyclic divinyl ketones containing fifteen and seventeen membered rings have been prepared in a single step by condensation of 1,3‐bis (dimethylphosphono)‐2‐propanone (10) with the dialdehydes 14, 17, 20, and 42 in the presence of hydrogencarbonate in aqueous t‐butyl alcohol at reflux without using high dilution techniques. The more highly unsaturated aldehydes give better yields and ketones 34 and 36, or mixtures of the two, were transformed to muscone (1) and Exaltone® by standard procedures. Civetone (2) was prepared by hydrogenation of 43 in pyridine solution. Dienone 29 appears to be the first α, β‐unsaturated ketone in which one of the β‐vinyl proton resonates at higher field than the corresponding α‐proton.
Crocetin‐dialdehyde from Coleus forskohlii BRIQ., Labiatae
Authors: Tandon Jai Shanker , Katti Seturam Bandacharya , Rüedi Peter , Eugster Conrad Hans 
Published: December 2004

AbstractAus den Wurzeln der im Titel genannten Labiate wurde Crocetin‐dialdehyd (8,8′‐Diapo‐carotin‐8,8′‐dial) (1), C20H24O2, isoliert. Chromatographisch wurde diese Verbindung auch in den oberirdischen Teilen dieser Pflanze nachgewiesen.
Einfache Synthese von 6‐[4‐Methyl‐3‐cyclohexen‐1‐yl]‐hept‐5‐en‐2‐on, einer Vorstufe für α‐Bisabolen und dessen Isopropenyl‐Isomers. Terpene und Terpen‐Derivate, 10. Mitteilung
Authors: Becker Manfred , Weyerstahl Peter 
Published: December 2004

Simple Synthesis of 6‐[4‐Methyl‐3‐cyclohexen‐1‐yl]‐5‐hepten‐2‐on, a Precursor of α‐Bisabolene and Its Isopropenyl IsomerThe alcohol 14 reacts with vinyl resp isopropenyl ether by Claisen rearrangement to give the aldehyde 16/17 resp. the ketone 3/4. Contrary to other reports this separable (E/Z)‐mixture also occurs as a result of the synthesis following the pathway 7 → 8/9 → 10/11 → 12/13 (see also [2]). The bisabolene isomers 5 resp. 6 are obtained by reaction of 3 resp. 4 with methylidene triphenyl phosphorane. A mixture of 1 and 5. however, is formed from 3 via the alcohol 18 and its acetate 19. Likewise 4 reacts via 20 and 21 to give a (2/6)‐mixture.
Stereospezifische Synthese von (+)‐(3R, 4R)‐4‐Methyl‐3‐heptanol, das Enantiomere eines Pheromons des kleinen Ulmensplintkäfers (Scolytus multistriatus)
Authors: Fráter György 
Published: December 2004

Stereospecific Synthesis of (+)‐(3R, 4R)‐4‐Methyl‐3‐heptanol, the Enantiomer of a Pheromone of the Smaller European Elm Bark Beetle (Scolytus multistriatus)Reduction of 2 with actively fermenting baker's yeast gave (−)‐3. Stereospecific alkylation [3] of (−)‐3 with propyl iodide furnished ethyl (+)‐(2R, 3R)‐2‐propyl‐3‐hydroxypentanoate ((+)‐4, 58%) which was converted to the tetrahydropyranyl ether (−)‐5, then the alcohol 6, the p‐toluenesulfonate 7 and the thiophenyl ether 8 to give the title compound (+)‐1. The latter consisted of 97% of the threo‐ and 3% of the erythro‐isomer. The above synthesis also correlates the absolute configuration of (−)‐(R)‐3 with that of (+)‐(R)‐citronellic acid (see [2]).
1,7‐Trimethylenenorbornane. A novel member of the ‘adamantaneland’. Preliminary communication
Authors: Jäggi Franz Josef , Ganter Camille 
Published: December 2004

AbstractA synthesis of the novel C10H16 hydrocarbon 1,7‐trimethylenenorbornane (13), one of the 19 members of the adamantane family, is described.
Metabolic Transformation of (3R, 4R)‐Δ1(7)‐Tetrahydrocannabinol by a Rat Liver Microsomal Preparation
Authors: Binder Michael , Barlage Uwe 
Published: December 2004

AbstractThe metabolism of the non‐psychotropic cannabinoid (3R, 4R)Δ1(7)‐tetrahydrocannabinol (1) (=Δ 1(7)‐THC) was investigated in a rat liver microsomal preparation. The metabolites obtained from the incubation mixture were separated, purified and identified by 1H‐NMR. spectroscopy and combined gas‐liquid chromatography/mass spectrometry. Metabolites 3–10 are derived from Δ1(7)‐THC (1) by mono‐hydroxylation in the isoprenoid moiety or the side chain of the molecule. Metabolites 11–16 are hydroxylated in the isoprenoid ring and the side chain simultaneously. The third group, metabolites 18–22, is derived from the 1,7‐epoxide 17 by hydrolysis of the oxirane ring, three of these metabolites bearing additional hydroxyl‐groups in the isoprenoid part or the side chain. The mass spectra of the metabolites are discussed in detail and a new rule for the fragmentations of tetrahydrocannabinols is presented.
Eine neue Synthese von 8‐Hydroxy‐2‐methyl‐1,2,3,4‐tetrahydroisochinolin
Authors: Gray Robert W. , Dreiding Andréa S. 
Published: December 2004

A new Synthesis of 8‐Hydroxy‐2‐methyl‐1,2,3,4‐tetrahydroisoquinolineVilsmeier formylation of N‐[2‐(3,5‐dimethoxyphenyl)ethyl]‐trifluoroacetamide (5) yielded the aldehyde 6, which under mild basic conditions was hydrolyzed to 7 and cyclized to 6,8‐dimethoxy‐3,4‐dihydroisoquinoline (3). Methylation of 3 and reduction of the double bond in 10 afforded 6,8‐dimethoxy‐2‐methyl‐1,2,3,4‐tetrahydroisoquinoline (11). The methoxyl group at C(6) was selectively demethylated and the free hydroxyl group in 12 was phosphorylated to give 13. Reduction of the latter with potassium in liquid ammonia yielded 8‐methoxy‐2‐methyl‐1,2,3,4‐tetrahydroisoquinoline (2), which was demethylated to the title compound 1.
Perkow Reaction Induced C,C‐Bond Formation
Authors: Winkler Tammo , Bencze William L. 
Published: December 2004

AbstractThe reaction of a cinnamoyl chloride with excess trimethyl phosphite gives a substituted 1,5‐hexadiene, in which C,C‐bond formation has taken place between the β‐C‐atoms of the two α, β‐unsaturated carbonyl moieties.
Photochemische Reaktionen. 107. Mitteilung. Zur Photochemie offenkettiger 2,6‐bzw. 2,7‐Dien‐Carbonylverbindungen
Authors: Yoshioka Michikazu , Ishii Keitaro , Wolf Hans Richard 
Published: December 2004

The Photochemistry of Open‐Chained 2,6‐ or 2,7‐Dien‐Carbonyl CompoundsOn 1n, π*‐excitation (λ > 347 nm) citral (5) and the methyl ketone 10 isomerize to compounds A (7, 19) and B (6, 20), whereas the phenyl ketone 11 changes into the isomer 24 of type E. Evidence is given that the conversions to A and B may arise from the 3n, π*‐state of the 2,6‐diene‐carbonyl compounds.On 1n, π*‐excitation (λ = 254 nm) 5 and 10 yield the isomers A (7, 19) and D (18, 22), but no products of type B. Furthermore, conversion of 10 to the isomer 21 of type C is observed.Selective 1n, π*‐excitation (λ = 254 nm) as well as selective 1n, π*‐excitation (λ > 347 nm) of the 2,7‐diene‐carbonyl compounds 12 and 13 give rise to isomerization to the compounds F (25, 28), exclusively. The intramolecular [2 + 2]‐photocycloadditions are shown to be triplet processes.UV.‐irradiation (λ > 280 nm) of compounds F (25, 28) furnishes the isomeric products G (26, 29) which photoisomerize to oxetanes of type H (27, 30).
Saponins with Molluscicidal Activity from Hedera helixL
Authors: Hostettmann Kurt 
Published: December 2004

AbstractFour triterpenoid saponins (1–4) have been isolated from the berries of Hedera helix L. (Araliaceae) by droplet counter‐current and preparative liquid chromatography. The structures have been established by FD./MS. and 13C‐NMR. spectroscopy. The isolated compounds were found to possess strong molluscicidal activity against the bilharziasis‐transmitting snail Biomphalaria glabrata. Saponin 4, identified as hederagenin 3‐O‐β‐D‐glucopyranosyl‐(1 → 2)‐β‐D‐glucopyranoside, is a new natural product.
Neue Wege zu 1H‐ und 2H‐Pyrrolen
Authors: Pfoertner Karl‐Heinz , Foricher Joseph 
Published: December 2004

New Routes to 1H‐ and 2H‐PyrrolesA synthesis of 1H‐pyrroles is described starting with pyridine analogues of chalcones and involving the reaction of acetic anhydride with 1‐pyrroline‐1‐oxides. Another route leads from 1‐pyrrolines to 2 H‐pyrroles via bromination with N‐bromosuccinimide and subsequent dehydrobromination in dimethylformamide.
Synthese von Diaza‐octahydroporphinato‐kobalt (III)‐Komplexen als Vitamin‐B12‐Modellverbindungen
Authors: Rytz Gerhard , Scheffold Rolf 
Published: December 2004

Synthesis of Octahydro‐porphinato‐cobalt(III) Complexes as Vitamin B12 Model CompoundsThe synthesis of (±)‐dibromo[1‐hydroxy‐2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18‐hexadecamethyl‐10,20‐diaza‐octahydroporphinato]cobalt(III) (2a) is described. The dicyano complex 2b and the corresponding annulene complex 3 have been obtained by exchange of its axial ligands and by elimination of the hydroxy group, respectively.
Crystal Structure of 4‐Trimethyltin‐quinuclidinium Perchlorate
Authors: Zehnder Margareta 
Published: December 2004

AbstractThe crystal structure of 4‐trimethyltin‐quinuclidinium perchlorate has been determined by direct methods and refined by least squares techniques. Crystals of C10H22ClNO4Sn are monoclinic, space group I2/c with lattice parameters a = 29.445 (13), b = 18.400(8), c = 11.300(5) Å, β = 95.82(5)°, V = 6090.65Å3, and two independent molecules (Z = 16), Interatomic distances are compared with those of known structures of quinuclidinium chloride and 4‐haloquinuclidinium chlorides and perchlorates.
Alcaloïdes bis‐indoliques de Catharanthus ovalis
Authors: Langlois Nicole , Andriamialisoa Ratremaniaina Z. , Neuss Norbert 
Published: December 2004

Bis‐indolic Alkaloids of Catharanthus ovalisVindolicine and fourteen bis‐indolic alkaloids of the vinblastine group have been isolated from the aerial parts of Catharanthus ovalis MGF. Three of them: vincovaline, vincovalinine and vincovalicine had not been previously isolated from a Catharanthus species.
1,2endo‐Trimethylenenorbornane. A novel isomer of adamantane
Authors: Jäggi Franz Josef , Ganter Camille 
Published: December 2004

AbstractAn easy approach to the novel adamantane isomer 1,2endo‐trimethylenenorbornane (2) is described. Starting from a mixture of pent‐4‐ynylcyclopentadienes 3 the tricyclic monosaturated key intermediate 5 was prepared by intramolecular cycloaddition (→4) and subsequent regioselective reduction of the C(5), C(6) double bond. The title hydrocarbon 2 was obtained from 5 upon stereoselective hydrogenation by diimide. In addition specifically deuteriated analogues of 2 were prepared applying dideuteriodiimide. Compound 2 rearranged to 2endo, 6endo‐trimethylenenorbornane (4‐homobrendane, 10) in sulfuric acid as well as with aluminium bromide in carbon disulfide.
Struktur eines O, N‐Ketenacetals: (1 RS, 8 SR, 10 SR, 4(15)Z)‐4‐äthyliden‐5‐oxa‐3‐azatricyclo [8.4.0.03,8]tetradecan
Authors: Kümin Albin , Maverick Emily , Seiler Paul , Vanier Noel , Damm Lorenz , Hobi Reinhard , Dunitz Jack D. , Eschenmoser Albert 
Published: December 2004

Structure of a O,N‐Keteneacetal: (1RS, 8SR, 10SR, 4(15)Z)‐4‐Ethylidene‐5‐oxa‐3‐azatricyclo [8.4.0.03,8]tetradecaneDie C‐Atome der äthylidenseitenkette der Titelverbindung 1 sind als C(15) und C(16) (s. Fig. 1) statt systematisch als C(1′) und C(2′) gekennzeichnet. Verbindung 1 kann auch als kondensiertes heterocyclisches Ringsystem benannt werden: 1‐äthyliden‐perhydro[1,3]oxazixino‐[3,4‐b]isochinolin.
Methods for the preparation of a series of model compounds which were required for stereochemical studies are described: the tricyclic O, N‐keteneacetal 1, the two diastereomeric bicyclic amino acids 7 and 10 (see Scheme 2), and the two diastereomeric conformationally fixed tetrahydro‐1,3‐oxazines (=1,3‐oxazixanes) 9 and 11.An x‐ray analysis of racemic 1 reveals a quasi‐tetrahedral nitrogen pyramid of the O, N‐ketene acetal grouping, and an almost perfect conformational analogy between the N‐ and C‐centered allylic positions at the double bond.