bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anil‐Synthese. 14. Mitteilung. Über die Darstellung von heterocyclisch substituierten Styryl‐Derivaten des 2H‐1,2,3‐Triazols
Authors: Siegrist Adolf Emil , Kormány Géza , Kabas Guglielmo 
Published: December 2004

Preparation of heterocyclic substituted styryl derivatives of 2H‐1,2,3‐triazole.Anile aus 2‐Phenyl‐4‐formyl‐2H‐1,2,3‐triazolen und o‐oder p‐Chloranilin können mit p‐tolyl‐substituierten aromatischen Heterocyclen in Gegenwart von Dimethylformamid und Kaliumhydroxid bzw. Kalium‐t‐butylat in die entsprechenden heterocyclisch substituierten Styryl‐Verbindungen übergeführt werden («Anil‐Synthese»). Zur Erzielung guter Ausbeuten muss das Reaktionsgemisch anfänglich mit ultraviolettem Licht bestrahlt werden. Die Darstellung heterocyclisch substituierter 4‐(2H‐1,2,3‐Triazol‐2‐ bzw. ‐4‐yl)‐styrol‐Verbindungen gelingt mit Natriummethylat ohne UV.‐Licht.
Stoffwechselprodukte von Mikroorganismen. 160. Mitteilung. Conocandin, ein fungistatisches Antibiotikum aus Hormococcus conorum (SACC. et ROUM.) ROBACK
Authors: Müller Johannes M. , Fuhrer Hermann , Gruner Johannes , Voser Walter 
Published: December 2004

Metabolites from Microorganisms. 160th Communication. Conocandin, a new Fungistatic Antibiotic.From a strain of Hormococcus conorum (SACC. ET ROUM.) ROBACK A 32′287, conocandin, a novel type C18‐fatty acid with high and specific in vitro fungistatic activity was isolated by means of counter current distribution and silicagel chromatography. The antibiotic is a viscous oil with the molecular formula C18H30O3. It is characterized by IR. and NMR. spectra, ester derivatives and the products of acid rearrangement and ozonolytic degradation. The structure of (E)‐2‐methylidene‐10‐methyl‐trans‐3,4‐epoxy‐9‐hexadecenoic acid (1) is proposed.
Germanium‐centered radicals. II. ESR. spectra of X‐irradiated single crystals of bis (triphenylgermyl) ether.
Authors: Geoffroy Michel , Ginet Lucien 
Published: December 2004

AbstractL'exposition d'un monocristal d'hexaphényldigermoxane aux rayons iomsants permet de piéger deux espèces radicalaires fortement localisées sur un atome de germanium. A partir des tenseurs de couplage hyperfin avec 73Ge on a calculé les caractères s et p de l'orbitale contenant l'électron non apparié au niveau du germanium. La comparaison de ces resultats avec ceux relatifs à \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Ph}_{\rm 3} {\rm G}\mathop {\rm e}\limits^ \bullet $\end{document} [1] montre qu'une des structures les plus probables pour un au moins de ces radicaux est du type \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_{\rm 3} {\rm G}\mathop {\rm e}\limits^ \bullet {\rm OR'}^ \ominus $\end{document}.
Selective Ether Cleavage in the Aporphine Series. Conversion of (S)‐Bulbocapnine into (S)‐Corytuberine and (S)‐Corydine Methyl Ether
Authors: Gerecke Max , Borer René , Brossi Arnold 
Published: December 2004

AbstractBulbocapnine methyl ether (2), on treatment with boron halides, affords the aporphine‐1,2‐diol (3), the novel aporphines 5 and 6 or the phenanthrene derivative 11 depending on the reaction conditions. 3 can be further transformed into corydine methyl ether (4); 6 has been converted to corytuberine (8). Similarly, dehydrobulbocapnine methyl ether 9 was converted to 10.
Stereochemistry of Polynuclear Cadmium(II)thioglycolates: Crystal Structure of [ICd8(SCH2CH2OH)12]3+ · 3I− · H2O
Authors: Beat Bürgi Hans , Gehrer Hermann , Strickler Peter , Winkler Fritz Karl 
Published: December 2004

AbstractCrystals of the title compound are triclinic, a = 27.87 Å, b = 10.77 Å, c = 12.94 Å, α 73.1°, β 116.1°, γ 120.0°, space group P1. The structure consists of octanuclear ions: Eight Cd(II) ions are found at the corners of a distorted cube, the center of the cube is occupied by an iodide, the twelve thioglycolate sulfur atoms bridge the twelve edges of the cube thereby forming a distorted icosahedron. Cadmium ions are either five or seven coordinate. The phase problem for this structure was solved using a combination of very high and very low E‐values.
Primary and Secondary Isotope Effects on Proton Transfers to Diazocarbonyl Compounds
Authors: McGarrity John F. 
Published: December 2004

AbstractThe primary solvent isotope effects on the ASE‐2 type hydrolyses of α‐diazocarbonyl compounds p‐XC6H4CN2CH3 (X = NO2, H, OCH3 and C6H5CON(CH3)2) are found to be identical despite large differences in their overall hydrolysis rates. The secondary solvent isotope effects diminish considerably with diminishing substrate reactivity, and for two substrates they are smaller than those normally anticipated for a simple proton transfer from the lyonium species. An analysis is presented of these and other abnormal secondary isotope effects found elsewhere, involving consideration of the solvation of the reaction complex.
Heterocyclic Spiro‐naphthalenones. Part VI. Some reactions with spiro [naphthalene‐2 (1H), 2′‐pyrrolidine]‐1,5′‐dione leading to various 6‐, 7‐, 8‐, 9‐, 10‐ and 11‐membered azacycloalkanes
Authors: Berney Daniel , Schuh Karlheinz 
Published: December 2004

AbstractThe spirolactam 5 was reduced to the spiro[naphthalene, pyrrolidine] 7 which was N‐aralkylated to give 9 and 17. Cyclization of 9 gave the phenanthridines 10 and 11; similarly, 17 afforded the 7‐ and 8‐membered heterocycles 18 and 19. Compounds 10, 18 and 19 when subjected to an intramolecular Hofmann elimination yielded the 9‐, 10‐ and 11‐membered ring systems, respectively 16, 22 and 23.
Photochemische Umsetzung von optisch aktiven 2‐(1′‐Methylallyl)anilinen mit Methanol
Authors: Scholl Bernhard , Hansen Hans‐Jürgen 
Published: December 2004

Photochemical Reaction of Optically Active 2‐(1′‐Methylallyl)anilines with MethanolIt is shown that (−)‐(S)‐2‐(1′‐methylallyl)aniline ((−)‐(S)‐4) on irradiation in methanol yields (−)‐(2S, 3R)‐2, 3‐dimethylindoline ((−)‐trans‐8), (−)‐(1′R, 2′R)‐2‐(2′‐methoxy‐1′‐methylpropyl)aniline ((−)‐erythro‐9) as well as racemic (1′RS, 2′SR)‐2‐(2′‐methoxy‐1′‐methylpropyl) aniline ((±)‐threo‐9) in 27.1, 36.4 and 15.7% yield, respectively (see Scheme 3). By deamination and chemical correlation with (+)‐(2R, 3R)‐3‐phenyl‐2‐butanol ((+)‐erythro‐13; see Scheme 4) it was found that (−)‐erythro‐9 has the same absolute configuration and optical purity as the starting material (−)‐(S)‐4. Comparable results are obtained when (−)‐(S)‐N‐methyl‐2‐(1′‐methylallyl)aniline ((−)‐(S)‐7) is irradiated in methanol, i.e. the optically active indoline (+)‐trans‐10 and the methanol addition product (−)‐erythro‐11 along with its racemic threo‐isomer are formed (cf. Scheme 3). These findings demonstrate that the methanol addition products arise from stereospecific, methanol‐induced ring opening of intermediate, chiral trans, ‐(→(−)‐erythro‐compounds) and achiral cis‐spiro [2.5]octa‐4,6‐dien‐8‐imines (→(±)‐threo‐compounds; see Schemes 1 and 2).
D‐Homosteroide I. Synthese von gestagen‐wirksamen D‐Homopregnan‐Derivaten
Authors: Müller Marcel , Alig Leo , Keller Peter , Fürst Andor , Kerb Ulrich , Wiechert Rudolf 
Published: December 2004

AbstractThe synthesis of a series of hormonally active D‐homopregnane derivatives is reported.
Synthesen von polyhalogenierten Butyrylchloriden, Vorläufern der pyrethroiden Haloketene
Authors: Martin Pierre , Steiner Eginhard , Belluš Daniel 
Published: December 2004

Synthesis of Polyhalogenated Butyryl Chlorides, Precursors of Pyrethroid HaloketenesThe copper (I)‐catalyzed free radical addition of halomethanes to acrylates and the addition of halogenated acetic acid derivatives to fluoro‐ or chloro‐substituted ethylenes affords polyhalogenated butyric acid derivatives. Chlorides of these acids serve as precursors for haloketenes used in efficient syntheses of pyrethroids.
Synthese optisch aktiver 2‐Methyl‐ und 2‐Äthyl‐1, 6‐dioxaspiro [4.4]‐nonan‐ und ‐[4.5]decan‐Pheromone aus einem gemeinsamen chiralen Vorläufer
Authors: Hungerbühler Ernst , Naef Reto , Wasmuth Daniel , Seebach Dieter , Loosli Hans‐Rudolf , Wehrli Adolf 
Published: December 2004

Synthesis of Optically Active 2‐Methyl‐ and 2‐Ethyl‐1, 6‐dioxaspiro [4.4]nonane‐ and ‐[4.5]decane Pheromones from a Common Chiral PrecursorThe versatility of the bromoepoxide6as chiral building block, which is readily available in both enantiomeric forms from malic acid, and which has previously been used for a vermiculine synthesis, is further demonstrated by the preparation of the title compounds1, 3, 4and5. Alkylation of 1,3‐dithiane, first with the 1‐ethoxyethyl‐protected ω‐chloroalcohols8bor9band then with the (S)‐(−)‐bromoepoxide6, followed by oxirane opening withSelectrideor methylGilman‐reagent creates the desired carbon skeletons and functionality patterns14–17, in overall yields of 60–80%. Acetal and thioacetal hydrolyses directly furnish the spiroacetal target structures1and3–5as 3:2‐diastereomeric mixtures; theE/Z‐epimers3are separated by preparative GC.(Fig.).
Linear Stereo‐co‐oligopeptides with Alternating D‐ and L‐Residues. I. Synthesis and Mass Spectrometric Behavior of the Members of a Series with Valine Residues
Authors: Tomasic Lera , Stefani Annibale , Lorenzi Gian Paolo 
Published: December 2004

AbstractThe synthesis of the protected stereo‐co‐oligopeptides with alternating D‐ and L‐valine residues Boc‐(D‐Val)m‐(L‐Val‐D‐Val)n‐OMe (m = 0; n = 1,2,3,4,6,8, and m = 1; n = 1,2,3,4) is described. The synthesis has been carried out by using conventional solution methods. The co‐oligopeptides up to the nonapeptide (m = 1; n = 4) have been prepared in a stepwise fashion. The dodecapeptide (m = 0; n = 6) and the hexadecapeptide (m = 0; n = 8) have been prepared by condensation of smaller peptides, and the criteria used for assessing their stereochemical purity are discussed. Preliminary characterization data are presented. Even the co‐oligopeptides with six or more residues, up to the dodecapeptide included, have given EI/MS. showing the molecular ion peak. The possible reasons for this uncommon behavior are examined.
2, 3‐Disubstituted γ‐Butyrolactams from the Michael‐Additions of Doubly Deprotonated, Optically Active β‐Hydroxycarboxylates to Nitroolefins. Preliminary Communication
Authors: Züger Max , Weller Thomas , Seebach Dieter 
Published: December 2004

AbstractThe conjugate addition of the chiral, non‐racemic alkoxy‐enolates 5 and 6 to nitroolefins furnishes the hydroxynitroesters 7–13, which are catalytically hydrogenated to give the lactams 14–18. The configuration of adduct 7 from nitroethylene was elucidated by NMR. analysis of the acetal 20 derived from 7. The assignment establishes that the reaction follows the stereochemical rule of attack depicted in 21 and previously deduced for other electrophiles, i.e. formation of erythro‐products of type 3b and 4b. No stereocontrol was found at the newly formed chiral centers in α‐ and β‐position to the NO2 group of 8–12.
High Acceleration and Improved Diastereoselectivity of Intramolecular Ene‐Type Reactions by Diethylaluminum Chloride. Preliminary Communication
Authors: Oppolzer Wolfgang , Robbiani Christian 
Published: December 2004

AbstractThe pyrrolidines 2 and 10 were obtained by thermal ene‐reactions at +70° and +180° from the (Z)‐4‐aza‐1, 6‐diene 1 and from the (E)‐4‐aza‐1, 6‐diene 9 in the ratios of 75:25 and 50:50, respectively. On the other hand, these cyclizations proceeded readily in the presence of diethylaluminum chloride at − 78° and − 35° giving in high yield the trans‐pyrrolidine 2 from 1 with 100% and from 9 with 89% diastereoselectivity.
Tieftemperatur 13C‐NMR.‐Spektren von 13C‐und 6Li‐markierten Chlor‐, Brom‐ und Jod‐Lithium‐Carbenoiden. Vorläufige Mitteilung
Authors: Scebach Dieter , Siegel Herbert , Gabriel Josef , Hässig Robert 
Published: December 2004

Low Temperature 13C‐NMR. Spectra of 13C‐ and 6Li‐Labelled Chloro‐, Bromo‐, and Iodo‐lithiumcarbenoidsThe 13C‐NMR. spectra of tetrahydrofuran solutions of 16 chloro‐, bromo‐, and iodo‐6lithio‐ and ‐7lithio‐carbenoids with 13C‐labelled methane, ethane, ethylene, and cyclopropane C‐skeletons have been measured at temperatures around − 100° (for examples see Fig. 1 and 2). Invariably, the exchange of hydrogen or halogen by lithium causes deshielding (Δδ, see Table 1) of the 13C‐signal by up to 289 and 434 ppm, respectively, and decrease of 1J (1H, 13C) and 1J(13C,13C) couplings (see Table 2) with the C‐atom of up to 104 and 30 Hz, respectively. The 1J(6Li, 13C) and 1J(7Li, 13C) coupling of ca. 17 and 45 Hz, respectively, obtained in ten cases (Table 1) is independant of the substitution pattern of the C‐skeleton and of the particular halogen atom.
Die Konstitution des Alkaloides Juliprosopin aus Prosopisjuliflora A. Dc. 176. Mitteilung über organische Naturstoffe
Authors: Ott‐Longoni Rita , Viswanathan Narayanaiyer , Hesse Manfred 
Published: December 2004

The Structure of the Alkaloid Juliprosopine from Prosopis juliflora A. Dc.A new alkaloid, juliprosopine, has been isolated from Prosopis juliflora A. Dc. (Leguminosae), for which structure 1 is proposed. The piperidine moiety could be elucidated on the basis of spectroscopic data (MS., 1H‐NMR., 13C‐NMR.) of juliprosopine and the derivatives 2–4. The central hexahydroindolizine part and its substitution pattern has been determined mainly on the bases of the Hofmann‐degradation product 11, which yielded the hydrogenation products 13 and 14. By ozonolysis 11 was converted to 16 and 18. It is proposed that juliprosopine was built up in nature by two ‘monomeric’ Prosopis alkaloids and one dihydropyrrol unit.
A Stereoselective Approach to the Spiro [4, 5]decane System via Intramolecular Photocycloaddition and Reductive Fragmentation. Preliminary communication
Authors: Oppolzer Wolfgang , Gorrichon Liliane , Bird T. Geoffrey C. 
Published: December 2004

AbstractThe photoaddition 6→7, followed by a reductive cleavage of the →‐chlorocyclobutylketone 7, gave the stereochemically pure spiro [4,5]decane 8.
Amidine als Zwischenprodukte bei Umamidierungsreaktionen. 9. Mitteilung über Umamidierungsreaktionen
Authors: Heidelberger Christian , Guggisberg Armin , Stephanon Euripides , Hesse Manfred 
Published: December 2004

Amidines as Intermediates in Transamidation ReactionsBy loss of water in the presence of p‐toluenesulfonic acid/xylole N‐aminoalkyllactames form bicyclic amidines. The corresponding N‐alkylaminoalkyl‐lactames' react to bicyclic amidinium salts or to transamidated products, ring‐enlarged by the N‐alkylamino residue, respectively (s. Scheme 1).The bicyclic amidines and amidinium salts are partially hydrolyzed by KOH/H2O to lactames (s. Scheme 2). Which of the two possible isomeric lactames are formed is discussed.
Propellanes. LXII. The endo‐ and exo‐adducts of 11‐cyano‐1,6‐methano[10] annulene with 4‐methyl‐1,2,4‐triazoline‐3,5‐dione
Authors: Ashkenazi P. , Kaftory M. , Arad D. , Apeloig Y. , Ginsburg D. 
Published: December 2004

AbstractThe title compounds have been isolated and their structures determined by X‐ray crystallography. Their relative stability is discussed in terms of theory and experiment. The endo‐adduct is the thermodynamically more stable one.
The Synthesis of Polyfunctional Aromatic Ring Systems. Structural Analogues of Phloroglucides, Aranciamycin, Cryptosporin and Terramycin
Authors: Hakimelahi Gholam Hosein , Moshfegh Ali Akbar 
Published: December 2004

AbstractThe synthesis of the title compounds is described. Some of the compounds prepared were found to be active against a number of pathogenic microorganisms in vitro.
Azidiniumsalze. 22. Mitteilung. über 3‐äthyl‐2‐tetrazo‐6‐X‐benzo[d]thiazoline und ihre Reaktivität: Ein Beitrag zur Chemie nucleophiler Carbene
Authors: Balli Heinz , Grüner Heinrich , Maul Rudolf , Schepp Horst 
Published: December 2004

3‐Ethyl‐2‐tetrazo‐6‐X‐benzo[d]thiazolines and Their Reactivity: A Contribution to the Chemistry of Nucleophilic CarbenesThe synthesis of 3‐ethyl‐2‐tetrazo‐6‐X‐benzo[d]thiazolines 3 ‐ a new class of azohomologous diazo compounds ‐ by addition of azide ions to azidinium salts 4 is described, their structure and some of their reactions are disscussed. The thermolysis of 3 at ca. 270 K in DMFA or THF generates nucleophilic carbenes 1, whose trapping by electrophilic compounds such as 3, 4, diazonium salts, diazo compounds, methanol, sulfur and tetracyanoethylene could be studied. Direct dimerisation of 1 to 2 (without acid/base catalysis) could not be found, as demonstrated by the behavior of 1e.
Enantiomer‐Selectivity for Phenylethylammonium Ion of Membranes Based on a Chiral Macrocyclic Polyether
Authors: Bussmann Walter , Simon Wilhelm , Oesch Urs , Lehn Jean‐Marie , Plumeré Pierre 
Published: December 2004

AbstractA chiral macrocyclic crown ether exhibits an enantiomer‐selectivity of 2.6 for α‐phenylethylammonium ion when incorporated in solvent polymeric membranes. The sequence of selectivity of these membranes clearly differs from that of lipophilicity for the different biogenic ammonium ions studied, indicating a significant structural contribution.
3‐Hydroxy‐4‐nitro‐cyclohexanone aus Ketonen und 4‐Nitrobuttersäurechlorid. Eine ringerweiternde Fünfringanellierung
Authors: Weller Thomas , Seebach Dieter , Davis Raymond E. , Laird Brian B. 
Published: December 2004

3‐Hydroxy‐4‐nitro‐cyclohexanones from Ketones and 4‐Nitrobutanoyl Chloride. A Ring Enlarging Five‐Ring AnnulationThe 6‐nitro‐1, 3‐diketones 5, 8, 9, 10, and 11, prepared by a 1:1 acylation at the C‐atom of non‐hindered lithium enolates with 4‐nitrobutanoyl chloride according to equation 3, are cyclized with sodium hydrogen carbonate in aqueous tetrahydrofuran to give the hydroxy‐nitro‐ketones 13–17. Such cyclic nitroaldols are not formed from the cyclopentanone, ‐heptanone, and ‐octanone, nor from the aryl derivatives 4, 6, 7 and 12, respectively. Except for the vicinally trisubstituted compound 14, the cyclization products are isolated in diastereomerically pure form. A crystal structure X‐ray analysis reveals the trans‐decalone and the cisβ‐nitroalcohol configurations of the product 13 from cyclohexanone (see Fig. 1–3). Acetalization to 21–25 and catalytic hydrogenation of the nitro groups furnishes the amino alcohols 27–31 (Table 4) which are substrates for the Tiffeneau‐Demjanow rearrangement (see Schemes 2, 3, 4 and 5), From the stereoelectronic control of this sextett rearrangement we deduce the configurations of the 1, 4‐diketones 35, 36, 39, 40, 43, 44, 46, and 47 formed under kinetic or thermodynamic conditions. The six‐ring annulation with nitrobutanoic acid and the subsequent rearrangement are shown in Scheme 6; the sequence of reactions described here allows to carry out a ring enlargement of a cyclic ketone by one C‐atom, with simultaneous annulation of a cyclopentanone ring.
Notiz über die Bestimmung der absoluten Konfiguration von (+)‐2‐Hydroxy‐2, 3‐dimethylbuttersäure
Authors: Wetter Hansjürg 
Published: December 2004

Note on the Determination of the Absolute Configuration of (+)‐2‐Hydroxy‐2, 3‐dimethylbutyric AcidChemical correlation of the title compound 1 with (S)‐3‐isopropyl‐3‐methyl‐5‐trimethylsilyl‐4‐penten‐2‐one (2) showed (+)‐1 to have (S)‐configuration. Key step was the Baeyer‐Villiger oxidation of a very hindered, optically active methyl keton to the corresponding acetoxy compound with trifluoroperacetic acid using slightly modified buffer conditions. It is found, that the erythro/threo assignment of an α, α‐disubstituted β‐hydroxyester intermediate can be based on the observation, that the 1H‐NMR. signal of HC(β) of the erythro isomer appears at lower field than that of the threo isomer.
The Ring Closure of Cyclopenta‐1, 3‐dien‐5‐yl‐carbene to Benzvalene. A mechanistic study of an unusual carbene reaction
Authors: Burger Ulrich , Gandillon Gérard , Mareda Jiri 
Published: December 2004

AbstractThe base‐induced α‐elimination of hydrogen chloride from 5‐chloromethyl‐5‐methylcyclopenta‐1, 3‐diene (19) produces 1‐methyltricyclo [3.1.0.02,6]hexene‐3 (1‐methylbenzvalene) (21) together with toluene and spiro [4.2]heptadiene (23). A common intermediate, 5‐methylcyclopenta‐1, 3‐dien‐5‐yl‐carbene (20), accounts for these results by intramolecular 1, 4‐carbene addition, 1, 2‐carbon shift and CH‐insertion, respectively. Independent synthesis of 2‐methylbenzvalene (24) allows us to show that the classic intramolecular cyclopropanation is completely suppressed by the linear cheletropic ring closure. MINDO/3 predicts the key carbene to have a bisected conformation in its singlet ground state. This ideally fulfills the stereoelectronic conditions for a carbene reaction of least motion. The influence of the methyl substituent upon that process is discussed.
Crystal Structure of (Z)‐1‐Phenyl‐ and of (Z)‐1‐Dimethylamino‐2‐phthalimido‐diazene‐1‐oxide
Authors: Hoesch Lienhard , Bieri Jost H. , Declercq Jean Paul , Germain Gabriel , Van Meerssche Maurice 
Published: December 2004

Kristallstruktur von (Z)‐1‐Phenyl‐ und von (Z)‐1‐Dimethylamino‐2‐phthalimido‐diazen‐1‐oxidDurch Röntgen‐Strukturanalyse wurden die Konstitution und die (Z)‐Konfiguration der im Titel genannten Produkte (3a und 3b) aus der Addition von Phthalimido‐nitren (1) an Nitrosobenzol (2a) bzw. an Dimethylnitrosamin (2b) im Einklang mit früheren, spektroskopischen Strukturzuordnungen bestätigt. In beiden Molekeln (3a und 3b) ist die Phthalimidogruppe nicht mit der Diazenoxidfunktion konjugiert, dagegen besteht offensichtliche Konjugation der zentralen NNO‐Funktion mit der Phenylgruppe in 3a bzw. mit der Dimethylaminogruppe in 3b. Die Ebene der NNO‐Gruppe ist in beiden Molekeln nur wenig gegenüber derjenigen der Substituenten an N(1) verdrillt (5° bei 3a bzw. 7° bei 3b). Die Bindungslänge zwischen N(1) und dem Dimethylamino‐Stickstoffatom in 3b entspricht mit 1,347 Å nahezu einer N,N‐Anderthalb‐Bindung, und beide zuletzt genannten N‐Atome sind coplanar mit ihren jeweiligen drei Liganden. Die Bindungslänge zwischen N(1) und dem benachbarten C‐Atom in 3a von 1,459 Å entspricht derjenigen einer Einfachbindung zwischen sp2‐hybridisierten N‐ bzw. C‐Atomen, analog den Bindungslängen zwischen N(1) und dem benachbarten C‐Atom in 1,2‐Diaryl‐diazen‐1‐oxiden (5; R, R′ = Aryl).
Proof of the Absolute Configuration of (−)‐(S)‐2‐Hydroxy‐β‐ionone by correlation with ursolic acid and with (−)‐trans‐verbenol
Authors: Escher Sina , Giersch Wolfgang , Ohloff Günther 
Published: December 2004

Abstract(−)‐(S)‐2‐Hydroxy‐β‐ionone (33), (+)‐(2 S, 6 S)‐2‐hydroxy‐α‐ionone (34), and their acetates 35 and 36 have been synthesized from (+)‐(S)‐6‐methylbicyclo [4.3.0]‐non‐1‐ene‐3, 7‐dione (3). The key intermediate (+)‐(1 R, 3 S, 6 S)‐2, 2, 6‐trimethyl‐7‐oxobicyclo [4.3.0]non‐3‐yl acetate (7) was correlated with a degradation product of the pentacyclic triterpene ursolic acid (16). Compound 33 was also synthesized by an alternative route starting from (−)‐trans‐verbenol (42).