bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dérivés du C‐méthyl‐3‐xylofurannose
Authors: Tronchet Jean M. J. , Tronchet Jeannine 
Published: December 2004

3‐C‐Methylxylofuranose Derivatives3′‐C‐methyladenosine has been known for almost ten years whereas its 3′‐epimer is still to be prepared, because of the difficulty of synthesizing the 3‐C‐methylxylo‐furanose. In this communication, the synthesis of 1,2‐O‐isoproypylidene acetal 9 and its derivatives is described. Vicinal dihydroxylation of 5‐O‐benzoyl‐3‐deoxy‐1,2‐O‐isopryopylidene‐3‐C‐methylidene‐α‐D‐erythro‐pentofuranose (6) led to the branchedchain sugar derivative 7 which was selectively tosylated to 8 whose reduction gave 9. These reactions, as well as the derivatizations of 7, 8 and 9, took place with good to excellent yields.
Bemerkungen zur Synthese von 5‐Amino‐m‐xylol‐2‐sulfonsäure und 5‐Amino‐m‐xylol‐4‐sulfonsäure
Authors: Courtin Alfred , von Tobel Hans‐Rudolf 
Published: December 2004

Some comments on the syntheses of 5‐amino‐m‐xylene‐2‐sulfonic acid and 5‐amino‐m‐xylene‐4‐sulfonic acidTreatment of 5‐amino‐m‐xylene (1) with oleum led to a 55:45 mixture of 5‐amino‐m‐xylene‐2‐sulfonic acid (2) and 5‐amino‐m‐xylene‐4‐sulfonic acid (3). The structure of both isomers was proven by reaction of sulfur dioxide with the diazonium chlorides derived from 2‐amino‐5‐nitro‐m‐xylene (5) and 4‐amino‐5‐nitro‐m‐xylene (8) giving 5‐nitro‐m‐xylene‐2‐sulfonyl chloride (6) and 5‐nitro‐m‐xylene‐4‐sulfonyl chloride (9) respectively, followed by hydrolyses to the corresponding sulfonic acids 7 and 10, and final Béchamp reductions. The sulfonic acid 2 was also prepared by sulfonation of 5‐acetylamino‐m‐xylene (4) to 5‐acetylamino‐m‐xylene‐2‐sulfonic acid (11) and subsequent hydrolysis. A further procedure for the synthesis of 3 was sulfonation of 5‐amino‐2‐chloro‐m‐xylene (12) – prepared by Béchamp reduction of 2‐chloro‐5‐nitro‐m‐xylene (13) – or of 5‐amino‐2‐bromo‐m‐xylene (15) – prepared by bromination of 4 and subsequent hydrolysis – to 5‐amino‐2‐chloro‐m‐xylene‐4‐sulfonic acid (16) and 5‐amino‐2‐bromo‐m‐xylene‐4‐sulfonic acid (17) respectively, followed by hydrogenolysis.
Kreuzkonjugierte Cyanine und Merocyanine aus Salzen des 1‐substituierten 2,3‐Dimethylchinoxalins (Vinyloge von Indigo‐imiden mit cyclisch eingebauter Imidfunktion). Vorläufige Mitteilung
Authors: Schelz Dieter 
Published: December 2004

Crossed conjugated Cyanines and Merocyanines, obtained from Salts of 1‐substituted 2,3‐Dimethyl‐quinoxalines. (A second type of vinylogous Indigo‐imides.) Preliminary Communication.On dissolving quaternary salts of 2,3‐dimethylquinoxaline in dimethylformamide or dimethylsulfoxide, a spontaneous reaction takes place: the title compounds are isolated from the reaction mixtures; they are easily oxidized, e.g. by MnO2. Mechanistic aspects are discussed.
Etude de l'action de l'oxyde d'azote (III) sur l'indène et ses homologues
Authors: Colette Maurice , Perrot Roger 
Published: December 2004

Addition of nitrogen trioxide to indene and alkylindenesN2O3 adds to indene and homologous yelding pseudonitrosites which are converted to aminoindanes. Treatment of the pseudonitrosites with alcoholic potassium hydroxide gives the correspondent nitroindenes.
Reactions with Carbo(heterylhydrazonoyl) Halides. I. Chemistry of Carbo(3‐phenylpyrazol‐5‐yl‐hydrazonoyl) Chlorides
Authors: Elmoghayar Mohamed Rifaat Hamza , Elnagdi Mohamed Hilmy , Ibrahim Mohamed Kamal Ahmed , Sallam Mohamed Mohamed Mohamed 
Published: December 2004

AbstractThe Carbo(3‐phenylpyrazol‐5‐yl‐hydrazonoyl) halides 1a,b react with active methylene compounds to yield the 1‐(3‐phenylpyrazol‐5‐yl)‐pyrazole derivatives 2a–k (Scheme 1). The acyclic intermediates 3a,b could be isolated from reaction of 1a,b with acetylacetone, thus establishing the substitution mechanism for these reactions.Compounds 1a, b reacted with carbon disulfide, phenyl isothiocyanate, methyl cyanide, and with p‐chlorobenzaldehyde to yield the corresponding heterocyclic derivatives 5–8, respectively (Scheme 2).The behaviour of compounds 2 with hydrazine hydrate is reported.
(E)‐9‐Isopropyl‐6‐methyl‐5,9‐decadien‐2‐one, a Terpenoid C14‐Ketone with a Novel Skeleton
Authors: Maurer Bruno , Ohloff Günther 
Published: December 2004

Abstract(E)‐9‐Isopropyl‐6‐methyl‐5,9‐decadien‐2‐one (1a), a terpenoid C14‐ketone with a novel skeleton, was isolated from costus root oil (Saussurea lappa CLARKE) and its structure established by a two‐step synthesis from thuja ketone (2). The possible role of the new compound as an intermediate in the biosynthesis of the irones is discussed.
Valence Ionization Energies of Hydrocarbons
Authors: Bieri Gerhard , Burger Fritz , Heilbronner Edgar , Maier John P. 
Published: December 2004

AbstractExperimental valence ionisation energies of 143 hydrocarbons, CnHm, have been determined from their He (IIα) (40.80 eV) and He (Iα) (21.22 eV) excited photoelectron spectra. Ionization energies, usually up to 26 eV are given in tabular form for 108 hydrocarbons with n≤6, together with their (tentative) assignment. The ionization energies up to approximately 25 eV, of 35 selected hydrocarbons with 7≤n≤10, are presented by means of their He (IIα) photoelectron spectra.
Application of the Equivalent Bond Orbital Model to the C2s‐Ionization Energies of Saturated Hydrocarbons
Authors: Bieri Gerhard , Dill James D. , Heilbronner Edgar , Schmelzer Andreas 
Published: December 2004

AbstractIt is shown that the ab initio STO‐3G treatment applied to simple saturated linear, branched and cyclic hydrocarbons, assuming standard geometries, yields orbital energies ϵ for their canonical orbital φj which correlate perfectly with the observed C2s ionization energies I, if Koopmans' approximation is accepted.Applying the Foster‐Boys localization procedure to these canonical orbitals φj leads to localized orbitals λμ and their corresponding Hartree‐Fock matrix Fλ = (Fλ,μv). An examination of the matrix elements Fλ,μv, i.e. of the self‐energies Aμ = Fλ,μμ of the localized CC‐ and CH‐orbitals λμ and of the cross terms Fλ, μv (μ ≠ v) between them, leads to the conclusion that a satisfactory approximation should be obtained by setting Aμ = A for all μ, Fλ,μv = B if λμ and λv are vicinal and neglecting all other cross terms. The resulting model is nothing but the well‐known equivalent bond orbital model of Lennard‐Jones & Hall, which however can now be calibrated using the known C2s‐ionization energies of hydrocarbons. Due to the discrete structure and the wider range (∽ 8 eV) of the C2s band systems in the photoelectron spectra of these molecules this leads to a more satisfactory parametrization than using the narrower and badly resolved C2p band system.Comparison of calculated band positions using the calibrated model with observed C2s‐band ionization energies for a series of hydrocarbons reveals that the simple equivalent bond orbital model is better than one might have expected.
Reaktionen von 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirin mit Phenolen und Halogenaromaten
Authors: Chandrasekhar B. Parthasarathi , Heimgartner Heinz , Schmid Hans 
Published: December 2004

Reactions of 3‐dimethylamino‐2,2‐dimethyl‐2H‐azirine with phenols and aryl halidesThe reactions of 3‐dimethylamino‐2,2‐dimethyl‐2H‐azirine (1) with phenols are described in chap. 1. The azirine 1 reacts with the 2‐formyl‐ and 2‐acetylphenols 5–8 to yield the N′‐methylidene derivatives of 2‐amino‐N,N‐dimethyl‐isobutyramide 9‐12 (Scheme 2, tautomeric form b). These products are in equilibrium with the tautomeric quinoide forms 9a‐12a. Under similar conditions 4‐hydroxybenzaldehyde did not react with 1. Reaction of 1 with 4‐hydroxycoumarine (13) gives the 4‐amino‐coumarine 14 (Scheme 2). The mechanism of these reactions is analogous to the previously reported one for the reaction of 1 with cyclic enolisable 1,3‐diketones [2] [3].Activated phenols with pKa‐values < 8, e.g. 2‐ and 4‐nitrophenol, 2,4‐dinitrophenol and pentachlorophenol, undergo addition reactions with 1 in boiling benzene solution to give the aniline derivatives 15‐18 (Scheme 3). A reaction mechanism is given in Scheme 3: after protonation of the azirine 1 followed by attack of the phenolate ion at the amidinium‐C‐atom, the intermediate of type e undergoes a rearrangement to the spiro‐Meisenheimer complexes of type f. Ring opening leads to 15–18. A similar reaction is observed for 2,4‐dinitro‐thiophenol and 1, giving 2‐(N′‐(2,4‐dinitrophenyl)amino)‐N,N‐dimethyl‐isobutyrothioamide (19).The azirine 1 reacts with the more acidic 2,4,6‐trinitrophenol (picric acid) to yield 3,3,6,6‐tetramethylpiperazine‐2,5‐bis(N,N‐dimethyliminium) dipicrate (21, Scheme 4). The methacrylamidinium salt 22 is the only product (97% yield) in the reaction of 8‐hydroxy‐5,7‐dinitroquinoline and 1 in acetonitrile solution. The reaction of 1 with picric acid can be explained in a similar way as the previously reported one with strong acids (cf. Scheme 1, [1] [3] [5]). An alternative mechanism without formation of the 1‐aza‐allylcation c is postulated in Scheme 5, together with a mechanism which could explain the exclusive formation of 22 in the reaction of 1 with 8‐hydroxy‐5,7‐dinitroquinoline.In chap. 2 a few reactions of the azirine 1 with aryl halides are reported. In the reaction with 2,4‐dinitrofluorobenzene it is shown by UV. and NMR., that m,n and o are intermediates (Scheme 6). Working up the reaction mixture with water, hydrogen sulfide or benzylamine leads to the aniline derivatives 17, 19 and 26, respectively. With picryl chloride and 8‐hydroxy‐5,7‐dinitroquinoline the azirine 1 undergoes a nucleophilic aromatic substitution to afford the intermediates p and q, which via deprotonation and ring opening give acrylamidine derivatives (27 and 29, Scheme 7 and 8). The steric hindrance in p and q between the aziridine ring and the two groups in o‐position could be the reason for the different behaviour of the intermediates n and p or q (cf. Schemes 6 and 8).
A New Synthetic Route to (±)‐Perhydrohistrionicotoxin
Authors: Corey E. J. , Petrzilka Martin , Ueda Yoichiro 
Published: December 2004

AbstractStarting from ethyl 2‐cyclohexen‐1‐carboxylate (3) the total synthesis of the perhydrohistrionicotoxin intermediate 23 was achieved in 25% overall‐yield. The two key steps involve a positionally specific addition of HOBr to the oxime‐olefin 7 and the alkylation of bromooxime 17 with 1‐lithio‐1‐butyne. The latter represents a novel method for stereospecific and position‐specific introduction of a nucleophilic butyl equivalent in α‐position to a ketonic carbonyl group.
Anil‐Synthese. 15. Mitteilung. Über die Herstellung von heterocyclisch substituierten Stilbenyl‐Derivaten des 2H‐1,2,3‐Triazols
Authors: Siegrist Adolf Emil , Kormány Géza , Kabas Guglielmo , Schläpfer Hans 
Published: December 2004

Preparation of heterocyclic substituted stilbenyl derivatives of 2H‐1,2,3‐triazoleSchiff's bases derived from 2‐ and 4‐(p‐formylphenyl)‐2H‐1,2,3‐triazoles and o‐ or p‐chloroaniline are reacted with various p‐tolyl substitued aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide or potassium t‐butoxide to yield the corresponding heterocyclic substituted stilbenes (“Anilsynthesis”). In order to avoid opening of the 2H‐1,2,3‐triazole ring, the reaction is carried out without external heating. In many cases an improvement in yield is obtained by irradiation with UV. light at the beginning of the reaction.
Konstitution und absolute Konfiguration der Rhoeadin‐Alkaloide (+)‐Alpinigenin und (+)‐cis‐Alpinigenin
Authors: Rönsch Hasso , Guggisberg Armin , Hesse Manfred , Schmid Hans 
Published: December 2004

The constitution and absolute configuration of the rhoeadine alkaloids (+)‐alpinigenine and (+)‐cis‐alpinigenine.The fundamental structure of the hemi‐acetal phenylbenzazepine alkaloid (+)‐alpinigenine (1), isolated from Papaver bracteatum LINDL., was derived essentially from 1H‐NMR.‐ and mass‐spectra of 1 and its derivatives 7, 10 and 14 (cf. Scheme 2). The positioning of the four methoxy groups in the two aromatic rings could be deduced from the 1H‐NMR.‐spectra of the N‐oxides 14 and 15 in which, as a result of favourable sterical and conformational behaviour, an interaction exists between the N‐oxide oxygen atom and one of the two ortho protons in ring C.The B/D‐trans‐fused 1 undergoes isomerization in 1N HCl to cis‐alpinigenine (16). A stereochemical correlation between bases in the trans‐and cis‐series was enabled via an Emde degradation of the corresponding methylacetal‐methyliodides 21 resp. 19 leading to the enantiomeric isochroman derivatives 22 resp. 23 which are achiral at C (2) (Scheme 4).The configuration at C (14) in the hemi‐acetals (eg. 1 and 16) and the methyl ethers (eg. 7 and 8) is discussed in detail (cf. Scheme 7). (+)‐Alpinigenine (1) has the (1S, 2R, 14R) configuration and (+)‐cis‐alpinigenine (16), in chloroform or acetone solution, the (1R, 2R, 14R) configuration.
Beitrag zur Massenspektrometrie substituierter α, ω‐Alkandiamine. 29. Mitteilung über massenspektrometrische Untersuchungen
Authors: Schöpp Emanuel , Hesse Manfred 
Published: December 2004

Contribution to the mass spectrometry of substituted α,ω‐alkane diaminesThe main mass spectral fragmentation pattern of compounds of types 1 to 4 is discussed. After loss of C6H5 · CH2 · from the molecular ion the acid correspondin to the N,N‐disubstituted residue is splitted off. The mechanism of this fragmentation reaction depends on the member of CH2‐groups between the two nitrogen atoms (Schemes 1 and 3) and on the substitution pattern of both nitrogens (Scheme 2).
Dimeric Radical Cation of 4,5,7,8‐Tetramethyl[2.2]paracyclophane
Authors: Bruhin Jürg , Gerson Fabian , Ohya‐Nishiguchi Hiroaki 
Published: December 2004

AbstractElectrolytic oxidation of 4,5,7,8‐tetramethyl[2.2]paracyclophane (I) yields a paramagnetic species which by ESR. spectroscopic evidence must be ascribed to the dimeric radical cation I2 · ⊕. Analogous dimers are obtained from the 12, 13, 15, 16‐tetradeuterio‐ and 1, 1, 10, 10, 12, 13, 15, 16‐octadeuterio‐derivatives of I so that all coupling constants can be unequivocally assigned to sets of equivalent protons. The hyperfine data for I2 · ⊕ are consistent with an effective D2h or D2d symmetry, the four benzene rings lying in parallel planes.
π‐Participation in Diazoketone Hydrolysis II; Exo‐endo Cyclization Ratio in the Hydrolyses of 7‐syn‐ and 5‐endo‐Diazoacetyl‐2‐norbornene
Authors: Malherbe Roger , Dahn Hans 
Published: December 2004

AbstractThe rate of the acid‐catalysed hydrosis of 7‐syn‐diazoacetyl‐2‐norbornene (1a) is enhanced relative to that of the saturated analogue 5a by a factor of 835. In contrast to the behaviour of other primary diazoketones, the substitution step is no longer rate‐determining (mechanism A‐2), but so much accelerated that the preceding proton transfer becomes the slow step (mechanism A‐SE2, demonstrated by a solvent isotope effect kH/kD = 1.76). Product analysis shows 100% cyclization; the product formation is explained in terms of brexyl and brendyl type carbenium ions (or ion pairs). ‐ 5‐endo‐Diazoacetyl‐2‐norbornene (3a) shows very slight acceleration, and forms only 27% cyclization products (identical to those formed from 1a). Thus, in spite of the absence of steric hindrance by hydrogen atoms, the exo‐endo rate ratio for anchimeric assistance is ≥ 103.
Réaction d'énamines dérivées de la cyclohexanone avec le tétracyanoéthylène
Authors: Hubschwerlen Christian , Fleury Jean‐Pierre , Fritz Hans 
Published: December 2004

Reaction with Tetracyanoethylene of Enamines derived from CyclohexanoneAt room temperature enamines of cyclohexanone react with tetracyanoethylene (TCNE) to give substituted tetrahydroindenes 5. The structures are assigned on the basis of 13C‐NMR. data and confirmed by hydrolysis. Spectroscopic studies (IR., UV., ESR.) at different temperatures indicate that the reaction can follow two routes: classical zwitterion formation, or a concurrent electron transfer between the enamines and TCNE leading to the derivates 5. These are the first reported examples of the γ‐carbon reactivity of an enamine.
On the Influence of Cholesterol Feeding and of a Lipogenic Diet on the Cholesterogenesis in Rat Liver in vivo
Authors: Oswald  , Wiss Verena 
Published: December 2004

Abstract
The existence of a main regulation site(s) of the cholesterol synthesis located after the squalene formation is demonstrated by cholesterol feeding with labelled glucose, acetate, mevalonate as precursors and by measuring the incorporation rates into cholesterol, squalene, ubiquinones, and fatty acids in rat liver in vivo.
By administration of labelled squalene in vivo it is shown that the isoprenic synthesis is inhibited between squalene and lanosterol but that other regulation site(s) after the lanosterol formation must exist.
A regulation site of the cholesterogenesis in rat liver located after the squalene synthesis is also shown after a lipogenic diet administered during 5 days. The cholesterol synthesis is thus reduced to about one third of the control rats. Another regulating site controlling the utilization of acetylcoenzyme A for the synthesis of mevalonate is also shown to exist. No indication was obtained for a regulating influence located between mevalonate and squalene.
Reaktionen von Steroiden mit Dialkylaminoschwefeltrifluoriden. I. 11β‐Hydroxysteroide. Über STeroide, 233. Mitteilung
Authors: Biollaz Michel , Kalvoda Jaroslav 
Published: December 2004

Reactions of Steroids with Dialkylaminosulfur Trifluorides. I. 11β‐Hydroxysteroids.Reactions of three types of 11β‐hydroxy steroids with dialkylaminosulfur trifluorides (DAST) have been studied. 9Δ‐unsubstituted 11‐alcohols are dehydrated with DAST to Δ9(11)‐unsaturated compounds under very mild conditions. 9α‐Chloro‐11β‐hydroxy steroids are quantitatively fluorinated in position 11 yielding the known 9α‐chloro‐11β‐fluoro derivatives. Finally, 9α, 11Δ‐fluorohydrins at 0–25° are selectively transformed with DAST into Δ11‐9α‐fluorides. When the latter reaction is run at lower temperature, the corresponding 11‐piperidinesulfinates, products of partial hydrolysis of the alkoxy‐dialkylaminosulfur difluoride intermediates postulated by Middleton, can be isolated in high yields. A rational explanation of the results is presented.
Charge‐Transfer‐Verbindungen mit Metallkomplexen. I. Bis(o‐phenylendiamido)‐Nickel‐Komplexe als Donatoren
Authors: Bäbler Fridolin , von Zelewsky Alexander 
Published: December 2004

Charge Transfer Compounds of Metal Complexes. I. Bis(o‐phenylenediamido)‐Nickel Complexes as DonorsThe synthesis of monosubstituted bis(o‐phenylenediamido)‐nickel complexes NiL2=Ni(C6H3(NH)2R)2 where R = H, OCH3, Cl, sec‐butyl, and of the disubstituted complex Ni(C6H2(NH)2 (CH3)2)2 is described. Substitution has a strong influence on the polarographically investigated reduction/oxidation behaviour of the complexes. Reaction of the nickel complexes with strong electron acceptors A (A = chloranil, tetracyanoethylene, 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone, 7,7,8,8‐tetracyanoquinodimethane) yields solid compounds with a stoichiometric composition NiL2: A = 1:1. IR. And UV./VIS. Spectroscopic data indicate an ionic ground state of the solids. Electrical conductivities of solids are in the range 4,3·10−3 ω−1 cm−1 to 5·10−12 ω−1 cm−1 at 298 K with activation energies of 0.33 eV to 1.68 eV.In some cases solution equilibria in acetone or dichloromethane have also been investigated. The general scheme is:
equation image
The tight ion pair NiLA− gives no ESR.‐signal. Low temperatures or addition of R4NClO4 salts favour the formation of the ionic species.
Beitrag zur asymmetrischen Synthese bicyclischer Verbindungen unter Katalyse mit optisch aktiven Aminosäuren. Synthese von (S)‐2‐Pyrrolidin‐propionsäure und (R)‐4‐Amino‐5‐phenylvaleriansäure
Authors: Buchschacher Paul , Cassal Jean‐Marie , Fürst Andor , Meier Werner 
Published: December 2004

Contribution to the asymmetric synthesis of bicyclic compounds catalysed by optically active amino acids. Synthesis of (S)‐2‐pyrrolidinepropionic acid and (R)‐4‐amino‐5‐phenylvaleric acidThe evaluation of literature data concerning the asymmetric cyclization of the prochiral monocyclic triketones 1 to the enediones 3 shows that catalysis with optically active α‐amino acids of the (S)‐series leads to an excess of products having the same absolute configuration as natural steroids at C (13), while those of the (R)‐series favour the formation of the enantiomers (Scheme 1). With 1a as substrate an inverse asymmetric course was observed using the optically active β‐amino acids 5, 8 and 10 as catalysts (Table 1). Furthermore, the synthesis of the optically active γ‐amino acids 6 and 11 using the Arndt‐Eistert process is described. The influence of these latter compounds on the asymmetric transformation of 1a into 3a has been investigated.
Identifizierung von Farnesol als Zwischenstufe in der Biosynthese des Cantharidins aus Mevalonsäurelacton. 7.Mitteilung zur Biosynthese des Cantharidins
Authors: Peter Martin G. , Woggan Wolf‐Dietrich , Schmid Hans 
Published: December 2004

Identification of farnesol as an intermediate in the biosynthesis of cantharidin from mevalonolactoneSimultaneous injection of 2‐[14C]‐mevalonolactone (2‐[14C]‐1) and (E,E)‐11′,12‐[3H]‐farnesol (11′,12‐[3H]‐2) into Lytta vesicatoria L. (Coleoptera, Meloidae) yields doubly labelled cantharidin (3). The remainder of the precursor farnesol, re‐isolated from the insects after the incubation period, has incorporated 14C‐radioactivity. The labelling pattern in this farnesol, as determined by two independent degradative reaction sequences, is in agreement with the isoprene rule. Since specific incorporation of farnesol (2) into cantharidin (3), and of mevalonolactone (1) into both, farnesol (2) and cantharidin (3) is observed, the sesquiterpene alcohol 2 acts as an intermediate in the biosynthesis of the C10‐compound 3 (Scheme 1).
Carotinoide aus marinen Schwämmen (Porifera): Isolierung und Struktur von sieben Hauptcarotinoiden ausAgelas schmidtii
Authors: Buchecker Richard , Eugster Conrad Hans , Litchfield Carter 
Published: December 2004

Carotenoids from Marine Sponges(Porifera): Isolation and Structure of the Seven Main Carotenoids fromAgelas schmidtiiThe following carotenoids were identified in the marine spongeAgelas schmidtii: α‐carotene ((6′R)‐β, ε‐carotene (1)), isorenieratene (φ,φ‐carotene (2)), trikentriorhodin (3,8‐dihydroxy‐κ,χ‐caroten‐6‐one (3)) and zeaxanthin ((3R, 3′R)‐β, β‐carotene‐3, 3′‐diol (4)). In addition, three previously unknown carotenoids called agelaxanthin A, B and C were isolated. Spectroscopical and chemical structure elucidation showed agelaxanthin A to be (3R)‐β, φ‐caroten‐3‐ol (6) and agelaxanthin C to be a methoxy‐19,3′,8′‐trihydroxy‐7,8‐didehydro‐β, κ‐caroten‐6′‐one (7) with the methoxy group at C (2), C (3) or C (4). The limited data on age‐laxanthin B were compatible with the structure of a 19‐O‐methyl derivative of agelaxanthin C.
A Highly Stereoselective Synthesis of C(11)‐Functionalized Aromatic Steroids by an Intramolecular Benzocyclobutene‐Olefin ‐Cycloaddition. Preliminary Communication
Authors: Oppolzer Wolfgang , Petrzilka Martin , Bättig Kurt 
Published: December 2004

AbstractThe racemiccis‐anti‐trans‐steroids9to11have been synthesized in a highly stereoselective manner starting from 4‐methoxybenzocyclobutene carboxylic acidviathe key step8→9. (cf. Scheme 2).