bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoinduzierte Reaktionen von 3‐Phenyl‐2H‐azirinen mit Carbonsäureestern 40. Mitteilung über Photoreaktionen
Authors: Gilgen Paul , Hansen Hans‐Jürgen , Heimgartner Heinz , Sieber Willi , Uebelhart Peter , Schmid Hans , Schönholzer Peter , Oberhänsli Willi E. 
Published: December 2004

AbstractIrradiation (280–350 nm light) of a benzene solution of 3‐phenyl‐2H‐azirines 1a–e in the presence of carboxylate esters, whose carbonyl groups are activated by electron withdrawing groups situated in the acyl or alkyl moiety, produces 5‐alkoxy‐3‐oxazolines (Tab. 1 and 4, Scheme 2) isolated in 18–82% yield. These heterocycles undoubtedly originate by regiospecific addition of the ester carbonyl group to the azirine‐derived benzonitrile‐methylide ‘dipole’ (Scheme 1). The 5‐(2,′ 2′, 2′‐trifluoroethoxy)‐3‐oxazolines, derived from 2′, 2′, 2′‐trifluoroethyl carboxylic esters, on treatment with methanolic hydrogen chloride at low concentration, are smoothly transformed into the corresponding 5‐methoxy‐3‐oxazolines (e.g. 16 → 17, Tab. 5). Utilizing this process, various hitherto relatively unknown 9. 5‐alkoxy‐3‐oxazolines become accessible.The constitution of the adducts is based essentially on spectral data. The structure of trans‐5‐methoxy‐2,4‐diphenyl‐5‐trifluoromethyl‐3‐oxazoline (trans‐14), the addition product of methyl trifluoroacetate and the benzonitrile‐benzylide from 2,3‐diphenyl‐2H‐azirine (1d), was determined by X‐ray crystallography (Section 5).Benzonitrile‐isopropylide (22), resulting from the photochemical transformation of 2,2‐dimethyl‐3‐phenyl‐2H‐azirine (1a), also reacts with S‐methyl thiobenzoate to give 2,2‐dimethyl‐5‐methylthio‐4,5‐diphenyl‐3‐oxazoline (26). Ethyl cyanoacetate protonates predominantly the dipolar species derived from 1a at the nitrile C‐atom and yields after work‐up ethyl α‐cyano‐cinnamate (29) and ethyl isopropylidene‐cyanoacetate (30) (Scheme 4).The relative rate of addition (krel) of benzonitrile‐isopropylide (22) to methyl α‐haloacetates and dimethyl oxalate was determined by competition experiments (Section 6). Log krel correlated satisfactorily (r = 0.97) with the pKa of the acide derived from the ester reactant: log krel = − 1.72 pKa + 2.58 or with Taft's substituent constants σ*: log krel = 2.06 σ* − 4.11 [krel(methyl dichloroacetate) = 1; Section 7.1].On the basis of the results obtained, the mode of reaction of the so‐called benzonitrile‐methylide ‘dipole’ is discussed and a model for the transition state of addition of ester‐carbonyl groups is proposed that accounts for the observed regiospecifity and steroselectivity.
An Efficient Photosensitizer: O‐Ethyl‐1‐thionaphthoate
Authors: Gisin Markus , Wirz Jakob 
Published: December 2004

AbstractThe title compound is recommended as a photosensitizer for excitation by visible light of up to 500 nm due to the following properties: high triplet yield, low singlet‐triplet splitting (ET = 55 kcal/mol), low photochemical reactivity.
Zum Lumineszenzverhalten von 9‐Fluorenon
Authors: Huggenberger Christian , Labhart Heinrich 
Published: December 2004

On the Luminescence of 9‐FluorenoneThe fluorescence of 9‐fluorenone has been measured in various solvents. At room temperature and for non‐hydrogen bonding solvents an emission with 19.3 ⩽ \documentclass{article}\pagestyle{empty}\begin{document}$ \widetilde\nu $\end{document}max ⩽ 21.4 · 103 cm−1 is found, whereas the fluorescence for hydrogen bonding solvents is broad and strongly red shifted, 16.7 ⩽ \documentclass{article}\pagestyle{empty}\begin{document}$ \widetilde\nu $\end{document}max ⩽ 17.5 · 103 cm−1. For these solvents also a strong temperature dependence of the emission characteristics is observed. The effects are attributed to hydrogen bonding of excited singlet fluorenone. Further, the phosphorescence of 9‐fluorenone is detected for ethanol and EPA (diethyl ether/2‐methyl‐butane/ethanol (99.5%) 5:5:2) solutions, locating the lowest triplet ππ* state at 17,600 cm−1.
The Synthesis of (S)‐(+)‐2‐Amino‐3‐(1‐adamantyl)‐propionic Acid (L‐(+)‐Adamantylalanine, Ada) as a ‘Fat’ or ‘Super’ Analogue of Leucine and Phenylalanine
Authors: Do Kim Quang , Thanei Peter , Caviezel Mario , Schwyzer Robert 
Published: December 2004

AbstractBecause of its overall steric resemblance to the phenylalanine analogue, carboranylalanine, the title compound was prepared by the modified Strecker synthesis of Patel & Worsley. The use of (S)‐(−)‐α‐methylbenzylamine in the synthesis, the positive trend of [α]D with increasing protonation, and the thin‐layer chromatographic behaviour of synthetic diastereomeric dipeptides are strong indications that the configuration at the asymmetric carbon atom is S (natural L). Its optical purity was ascertained by purification via the quinine and ephedrine salts of t‐butoxy‐carbonyl‐adamantylalanine. The new amino acid shall be used for studies of structure‐activity relationships of phenylalanine and leucine residues in biologically active peptides. In addition, a convenient synthesis in excellent yield of the starting material, 2‐(1‐adamantyl)‐ethanal, by Pfitzner‐Moffat oxidation of 2‐(1‐adamantyl)‐ethanol is described.
Nucleotide. X. Synthese und Eigenschaften von Dinucleosidmonophosphaten mit 2′‐Desoxyadenosin und 1‐(2′‐Desoxy‐β‐D‐ribofuranosyl)‐lumazinen als Bausteine
Authors: Charubala Ramamurthy , Pfleiderer Wolfgang 
Published: December 2004

Nucleotides. X. Synthesis and properties of dinucleoside monophosphates with 2′‐deoxyadenosine and 1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐lumazines as building blocksThe synthesis of various dinucleoside monophosphates 16‐‐20 consisting of 2′‐deoxyadenosine and 1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐lumazines via the triester approach is described. The fully protected phosphotriesters 6‐‐10 as well as the partially deblocked intermediates 11‐‐15 have also been isolated and characterized by physical means. Intramolecular interactions in 16‐‐20 have been investigated by the determination of the hypochromicities and CD. spectra revealing a more or less distinct stacking effect in dependence of the 6,7‐substituents in the lumazine moiety as well as the polarity of the internucleotidic linkage. Enzymatic degradations of the dinucleoside monophosphates with snake venom and spleen phosphodiesterase are depending strongly on various structural features indicating a much lower substrate specificity especially in presence of 6,7‐diphenyl‐lumazine as an aglycone with the latter enzyme.
Formation of Dichloro Oxiranes from Ketones under Phase Transfer Conditions,
Authors: Greuter Hans , Winkler Tammo , Belluš Daniel 
Published: December 2004

AbstractCompounds 2, 5 and 9 represent the first examples of isolable dichlorooxiranes formed by formal addition of dichloro carbene to a carbonyl group under phase transfer conditions. On heating, 2, 5 and 9 rearrange into α‐chloroacid chlorides 3, 6 and 10, respectively.
Die Synthese von 3β‐Acetoxy‐24‐aza‐24‐desoxa‐xysmalogenin,. Partialsynthetische Versuche in der Reihe der Herzgifte. 12. Mitteilung,
Authors: El‐Dine Shams , Faust Karin , Güntert Theodor W. , Hauser Emil , Linde Horst H. A. , Spengel Sigrid 
Published: December 2004

Synthesis of 3β‐acetoxy‐24‐aza‐24‐desoxa‐xymalogeninStarting from the pregnenolone‐derivative 1 we report the synthesis of the possibly cardiac‐active compound 24‐aza‐24‐desoxa‐xysmalogenin 15.
Two Furanosesquiterpene Marine Metabolites with Antifeedant Properties
Authors: Schulte Gary , Scheuer Paul J. , McConnell Oliver J. 
Published: December 2004

AbstractTwo new sesquiterpenoids, nakafuran‐8 (1) and −9 (8), have been isolated from the marine sponge Dysidea fragilis and from its prey, the nudibranchs Hypselodoris godeffroyana and Chromodoris maridadilus. The structures were established by spectral analysis and chemical transformations. Both compounds possess antifeedant properties when assayed in the laboratory against common reef fishes, Chaetodon spp.
Regioselektive Metallierung des Phenylcyclopropans sowie leichte Anlagerung des 1‐Phenylcyclopropyl‐kaliums an Äthylen
Authors: Schlosser Manfred , Schneider Philippe 
Published: December 2004

Regioselective Metalation of Phenylcyclopropane and Smooth Addition of 1‐Phenylcyclopropyl Potassium onto EthyleneWhereas pentyl sodium in pentane mainly promotes a hydrogen/metal exchange reaction at the m‐ and p‐position of phenylcyclopropane, both the butyllithium/potassium t‐butoxide reagent and trimethylsilylmethyl potassium in tetrahydrofuran convert phenylcyclopropane exclusively into 1‐phenylcyclopropyl potassium. The latter organometallic derivative adds smoothly onto the double bond of ethylene at temperatures around −40°.
Regio‐ and Stereoselective Functionalizations of Tricyclo [3.3.0.02,8]octan‐3‐one, a Potential Synthon for Polycyclopentanoid Terpenes and Prostacyclin Analogs. Preliminary Communication
Authors: Demuth Martin , Chandrasekhar Sosale , Nakano Koichi , Raghavan Palaykotai R. , Schaffner Kurt 
Published: December 2004

AbstractChemical transformation of tricyclo [3.3.0.02,8]octan‐3‐one (1) have been carried out in order to explore its potential utility as a versatile synthon for polycyclopentanoid terpenes and prostacyclin analogs. Various functionalizations of rings A and B and annulation of a third ring C were achieved in generally high yields. The system provides for a large measure of regio‐ and stereoselective reaction control.
Unambiguous Proof for Alcoxycarbonyl‐group Migration in Wagner‐Meerwein Rearrangements
Authors: Berner Daniel , Dahn Hans , Vogel Pierre 
Published: December 2004

AbstractIn HSO3F/SO2ClF the β‐hydroxy esters Ph‐CHOH‐CMe2‐COOR (1, RMe, Et) are doubly protonated, then transformed into the fluorosulfates 7 and (partly) into the fluorides 8. At −15°, both 7 and 8 undergo a rearrangement, forming derivatives of Me2CC(Ph)COOR (2). By labelling 1 with 13C, singly (13C(3)) and doubly (13C(1,3)), it could be shown that exclusively the ROOC groups undergo a 1,2‐shift. Compound 2 is also formed in HSO3F/SO2ClF from the isomeric Me2COH‐CHPh‐COOR (3) by elimination, and less easily from the α‐hydroxy ester Ph‐CMe2‐CHOH‐COOR (5) via a phenyl 1,2‐shift. Another isomer, Ph‐C(OH)Me‐CHMe‐COOR (4) gives products different from 2.Using more acidic systems containing SbF5, the free carbenium ions 13 (Ph‐CH+‐CMe2‐COOR) can be stabilized; they do not form 2, possibly because of complexation of the ester group with SbF5. The energy profile and the mechanism of the rearrangement 1 → 2 are discussed.
Persistance of the Cyclopnane Radical Anions and its Relation to Structure
Authors: Gerson Fabian , Lopez Javier , Boekelheide Virgil , Hopf Henning 
Published: December 2004

AbstractReactions of [2N]cyclophanes (N = 2, ⃛6) with solvated electrons in 1,2‐di‐methoxyethane at 193 K have been studied by ESR. and ENDOR. spectroscopy. All but the two most highly bridged cyclophanes (N = 5 and 6) are reduced to paramagnetic species under these conditions. Whereas the radical anions of [2.2]‐paracyclophane and [23](1,2,4)‐ and [24](l,2,4,5)cyclophanes are sufficiently persistent to be characterized by their hyperfine data, those of the remaining five cyclophanes undergo a rapid cyclization to the radical anions of 4,5,9,10‐tetrahydropyrenes. These have been identified as the unsubstituted tetrahydropyrene (from [2.2]‐metacyclophane and [23](l,2,3)cyclophane), the 2,7‐dimethyl‐derivative (from [23](1,3,5)‐ and [24](l,2,3,5)cyclophanes) and the 1,8‐dimethyl‐derivative (from (24l,2,3,4)cyclophane). The persistence of the cyclophane radical anions seems to depend on the numbers, nmeta and npara, of the meta‐and para‐positions of the bridging ethano groups in the two benzene rings. The prerequisite for the radical anion to be persistent is nmeta⩽npara.
Steric Effects on Reaction Rates. IV. Evaluation of the Ketone Model for the Solvolysis Transition State of Secondary p‐Toluenesulfonates
Authors: Müller Paul , Blanc Jacky , Pcrlberger Jean‐Claude 
Published: December 2004

AbstractThe rates of solvolysis of secondary p‐toluenesulfonates in acetic acid or 97% trifluoroethanol are interpreted in terms of strain changes between substrate and the corresponding ketone. Such strain changes are obtained from force‐field calculations (ΔEst) and from equilibration of alcohols and ketones (ΔGox). This simple model reproduces the behaviour of substrates reacting by kc‐pathways to afford unstrained carbenium ions. Anchimeric assistance and leaving group hindrance in the transition state are recognized in clear‐cut cases by deviations from the expected reactivity. However, the model breaks down when highly strained carbenium ions of the cyclobutyl or 7‐norbornyl type are involved.
Acid‐Catalyzed Rearrangements of Vinylketene/Cyclopentadiene Adducts
Authors: Huston Rima , Rey Max , Drieding André S. 
Published: December 2004

Säurekatalysierte Umlagerungen von Vinylketen/Cyciopentadien‐AdduktenVier Alkyl‐vinylketene (7b–e), in situ durch 1,4‐Eleminierung von HCl aus den entsprechenden α,β‐ungesättigten Acylchloriden hergestellt, wurden mit Cyclopen‐tadien umgesetzt. Durch [2 + 2]‐Cycloaddition entstanden 7‐alkyl‐7‐vinylsubstituierte Bicyclo[3.2.0]hept‐2‐en‐6‐one 8/9. Das Stereoisomerenverhältnis 8:9 hängt von der relativen Grösse der Ketensubstituenten ab. Die Vinylketen/Cyclopen‐tadien‐Addukte 8/9 enthalten ein α‐Vinylcyclobutanon‐, ein Cope‐ und (bei 8f) ein Allylchlorid‐System. Unter dem Einfluss von Säuren (meistens BF3‐Ätherat) wurden bei 8/9 vier verschiedene Typen von Umlagerungsreaktionen beobachtet, nämlich, je nach dem Substitutionsmuster: [l,3]‐Alkyl‐Wanderungzu Bicyclo[4.3.0]‐nonadienonen 12, [l,2]‐Acyl‐Wanderung zu Bicyclo[3.3.0]octenonen 13, [3,3]‐Cope‐Umlagerung zu Bicyclo[4.2.1]nonadienonen 14 oder [l,3]‐Halogen‐Wanderung zu 7‐AlkylidenbicycIo[3.2.0]heptenonen 15. Die [l,3]‐Alkyl‐ und [l,2]‐Acyl‐Wanderun‐gen konkurrieren mit der Cope‐Umlagerung, wobei auch die Konfiguration an C(7) der Vinylketen/Cyclopentadien‐Addukte (8 bzw. 9) und das Lösungsmittel eine Rolle spielen können.
Isolierung und Strukturermittlung der neuen Cyclosporine E, F, G, H und I
Authors: Traber René , Loosli Hans‐Rudolf , Hofmann Hans , Kuhn Max , Wartburg Albert Von 
Published: December 2004

Isolation and Structure Determination of the New Cyclosporins E, F, G, H und IThe cyclosporins, a new group of biologically active metabolites, are produced by the fungus Tolypocladium inflatum GAMS (formerly designated as Trichoderma polysporum [LINK EX PERS.] RIFAI). They represent neutral cyclic oligopeptides composed of 11 amino acids. In addition to the already described cyclosporins A–D new minor compounds, cyclosporins E–I, have now been isolated from the crude cyclosporin‐complex by applying extensive chromatographical separation procedures. The structures of the new compounds have been determined by spectroscopical evidence, hydrolytic cleavage and chemical correlation reactions as well as by X‐ray analysis of suitable derivatives. Cyclosporins A, B, C, D and G differ from each other only in the nature of the amino acid no. 2. Cyclosporins E and I are N‐demethylated congeners of cyclosporins A and D respectively, Cyclosporin F has been recognized as deoxycyclosporin A, whereas Cyclosporin H represents an epimeric form of cyclosporin A and contains N‐methyl‐D‐valine in position 11.
15N‐NMR Spectroscopic Characterization of Triaziridines
Authors: Hilpert Hans , Hollenstein Roger 
Published: December 2004

AbstractThe 15N‐NMR spectra of cis‐ and trans‐2,3‐dialkyl‐substituted triaziridines are reported. The assignment of the 15N‐NMR resonances is described, and the chemical‐shift and coupling data are compared with those of aziridines and diaziridines. The 1J(N,H) coupling constants allow one to deduce the relative configuration of the involved N‐atom. In CDCl3, a 1J(N,H) value of 58.1 ± 0.5 Hz is assigned to an NH bond cis to two lone‐pairs of electrons at neighboring N‐atoms, i.e. to the cis,trans‐triaziridinesThe first stereodescriptor denotes the relative configuration of the two equal alkyl substituents, the second the relative configuration of one alkyl substituent and the H‐atom.
, and a value of 51.7 ± 0.5 Hz is assigned to a NH bond cis to only one lone‐pair of electrons, i.e. to trans, cis‐triaziridines.
Formation of Cyclic ‘ortho’‐Anhydrides of Heptalene‐1,2‐dicarboxylic Acids
Authors: Weber Roland H. , Brügger Paul , Arnold Wolf , Schönholzer Peter , Hansen Hans‐Jürgen 
Published: December 2004

Abstract1‐(Alkoixycarbonyl)heptalene‐2‐carboxylic acids as well as 2‐(alkoxycarbonyl)heptalene‐1‐carboxylic acids react with the iminium salt formed from N,N‐dimethylformamide (DMF) and oxalyl chloride, in the presence of an alcohol, to yield the corresponding cyclic ‘ortho’ ‐anhydrides (ψ‐esters; cf. Schemes 2,3,6, and 8). When the alkoxy moiety of the acids and the alcohols is different, then diastereoisomeric ‘ortho’ ‐anhydrides are formed due to the non‐planarity of the heptalene skeleton. The approach of the alcohol from the β‐side is strongly favored (cf. Scheme 5 and Table 1). This effect can be attributed to the bent topology of the heptalene skeleton which sterically hinders the approach of the nucleophile from the α‐side of the postulated intermediates, i.e. the charged O‐alkylated anhydrides of type 19 (cf. Scheme 6). Whereas the ‘ortho’‐anhydrides with four substituents in the ‘peri’ ‐positions of the heptalene skeleton are configurationally stable up to 100°, the ‘ortho’ ‐anhydrides with only three ‘peri’ ‐substituents slowly epimerize at 100° (cf. Scheme 7) due to the thermally induced inversion of the configuration of the heptalene skeleton.
Catalytic Intramolecular Palladium‐Ene Reactions. Preliminay Communication
Authors: Oppolzer Wolfgang , Gaudin Jean‐Marc 
Published: December 2004

AbstractPd(dba)2[dba = dibenzylideneacetone]/PPh3‐or Pd(PPh3)4‐catalyzed cyclizations of acetoxy‐dienes 2 → 3 and 10 → 11 gave 1‐vinyl‐2‐methylidene‐subsituted cyclopentances and cyclohexanes in high yield, consistent with a palladium‐ene/β‐elimination mechanism (D → E → F, Scheme 2). The efficient and highly stereoselective cyclizations 7 → 7 and 8 → 9 illustrate intramolecular allylpalladium insertions into 1,2‐dialkyl‐, trialkyl‐, trialkyl‐, and cyclic alkenes followed by elimination of the exocyclic β–H giving 1,2‐divinylcyclopentanes. These new olefin insertions proceed faster in AcOH (compared to THF) and occur preferentially cis relative to the Pd (13 → 14 → 15).
Nucleophile Ringöffnung von α‐Nitrocyclopropancarbonsäure‐arylestern mit sterisch geschützter, aber elektronisch wirksamer Carbonyl‐ und Nitro‐Gruppe. Ein neues Prinzip der α‐Aminosäure‐Synthese (2‐Aminobutansäure‐a4‐Synthon)
Authors: Seebach Dieter , Häner Robert , Vettiger Thomas 
Published: December 2004

Nucleophilic Ring Opening of Aryl α‐Nitrocyclopropanecarboxylates with Sterically Protected but Electronically Effective Carbonyl and Nitro Group. A New Principle of α‐Amino Acid Synthesis (2‐Aminobutanoic Acid a4‐Synthon)The readily available 2,4,6‐tri(tert‐butyl)‐and 2,6‐di(tert‐butyl)‐4‐methoxypahenol esters 2 of α‐nitrocyclo‐propanecarboxaylic acid ring opening with C‐, N‐, O‐, and S‐nucleophiles (cyanide, malonate, azide, anilines, alkoxides, phenoxides, thiolates) in DMF or alcohol solvents (80–95% yield). The products 6–14 are 2‐nitrobutanoates with the newly introduced substituent in the 4‐position. Reduction of the NO2 group with Zn/AcOH/Ac2O gives N‐acetyl‐α‐amino acid esters 16–22 (40–90% yield). Subsequent oxidative cleavage (H2O2/HCOOH) of The p‐methoxy‐phenyl esters 18 and 20 produces free amino acids (65% 23 and 67% 24, respectively). Thus, the nitro ester 2 corresponds to a 2‐aminobutanoic‐acid a4‐synthon, it is a ‘homo‐Michael acceptor’ producing γ‐substituted α‐amino acids.
Notiz über die Verwendung von 3‐(Arylsulfonyl)‐2‐cycloalkenonen als 2‐Cycloalkinon‐Synthese‐Equivalente
Authors: Kienzle Frank , Minder Rudolf E. 
Published: December 2004

Note on the Use of 3‐(Arylsulfonyl)‐2‐cycloalkenones as Synthesis Equivalents of 2‐Cycloalkynones3‐(Arylsulfonyl)‐2‐cyclopentenones and 3‐phenylsulfonyl‐2‐cyclohexnone undergo Diels‐Alder reactions with cyclopentadiene. Elimination of arylsulfinic acid leads to products, which would have been obtained directly from a Diels‐Alder reaction of 2‐cyclopentynone or 2‐cyclohexynone.
Cyclodimerization of 1‐(Dimethoxyniethyl)‐5,6‐dimethylidene‐7‐oxa‐bicyclo[2.2.1]hept‐2‐ene Induced by Nonacarbonyldiiron. Crystal Structure of (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)‐ Tricarbonyl[C, 2,3, C‐η‐(1,4‐epoxy‐1,5‐bis(dimethoxymethyl)‐2,3‐dimethylidene‐1,2,3,4,4a,9,9a,10‐octahydroanthracene)]iron
Authors: Bonlantini Edia , Vogel Pierre , Pinkerton Alan A. 
Published: December 2004

AbstractThe transition‐metal‐carbonyl‐induced cyclodimerization of 5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene is strongly affected by substitution at C(1) While 5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]hept–2‐ene‐l‐methanol (7) refused to undergo [4 + 2]‐cyclodimerization in the presence of [Fe2(CO)9] in MeOH, 1‐(dimethoxymethyl)‐5,6‐di‐methylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene (8) led to the formation of a 1.7:1 mixture of ‘trans’ (19, 21, 22) vs. ‘cis’ (20, 23, 24) products of cyclodimerization together with tricarbonyl[C, 5,6, C‐η‐(l‐(dimethoxymethyl)‐5,6‐di‐methylidenecyclohexa‐1,3‐diene)]iron (25) and tricarbonyl[C,3,4, C‐η‐(methyl 5‐(dimethoxymethyl)‐3,4‐di‐methylidenecyclohexa‐1,5‐diene‐l‐carboxylate)]iron (26). The structures of products 19 and of its exo (21) and endo (22) [Fe(CO)3(1,3‐diene)]complexes) and 20 (and of its exo (23) and endo (24) (Fe(CO)3(1,3‐diene)complexes) were confirmed by X‐ray diffraction studies of crystalline (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)‐tricarbonyl[C, 2,3, C‐η‐(1,4‐epoxy‐1,5‐bis(dimethoxymethyl])‐2,3‐dimethylidene‐1,2,3,4,4a,9,9a,10‐octahydroanthracene)iron (21). In the latter, the Fe(CO)3(1,3‐diene) moiety deviates significantly from the usual local Cs symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η‐alkyl, η3‐allyl bonding mode due to the acetal unit at the bridgehead centre C(1).
Biologically Active Natural Acetylenic Compounds from Eutypa lata (Pers: F.) TUL
Authors: Renaud Jean‐Marc , Tsoupras Georges , Tabacchi Raffaele 
Published: December 2004

AbstractEight new acetylenic compounds have been isolated and identified from the culture medium of the fungus Eutypa lata. Structural elucidation and biological activity are discussed.
Novel Prenylated Xanthones from Garcinia gerrardii HARVEY
Authors: Sordat‐Diserens Isabelle , Marston Andrew , Hamburger Matthias , Hostettmann Kurt , Rogers Colin 
Published: December 2004

AbstractThree novel prenylated xanthones, 1–3, have been isolated from the root bark of Garcinia gerrardii HARVEY ex T. R. SIM (G. natalensis SCHLECHTER; G. transvaalensis BURTT DAVY; Guttiferae). Structure elucidation was achieved by a combination of one‐ and two‐dimensional NMR spectroscopic techniques, including long‐range HETCOR, mass spectroscopy, and chemical methods. Garcigerrin A (1) and B (2) are pyrano derivatives of 3. They all show a rare 1,4,5 oxygenation pattern of the xanthone nucleus. Xanthone 3 is fungicidal against Cladosporium cucumerinum.
Conversion of Campholene‐ to Necrodane‐Type Monoterpenes. A short stereoselective synthesis of (−)‐(R, R)‐β‐necrodol and its three stereoisomers
Authors: Schulte‐Elte Karl H. , Pamingle Hervé 
Published: December 2004

AbstractApplication of a stereoselective Prins/retro‐Prins rearrangement sequence from (−)‐(R)‐campholenyl acetate((−)‐4) opens a new access to the naturally occurring (−)‐(R, R)‐β‐necrodol ((−)‐1) and its three stereoisomers with high optical purity.
Highly Regioselective Nitration of Hexamethylbenzene and Its Derivatives to Dinitroprehnitene with Excess Nitronium Tetrafluoroborate
Authors: Surya Prakasb G. K. , Wang Qi , Li Xing‐Ya , Olah George A. 
Published: December 2004

AbstractHexamethylbenzene and its derivatives undergo very clean regioselective dinitration to dinitroprehnitene (1, 2, 3, 4‐tetramethyl‐5, 6‐dinitrobenzene) with excess of nitronium tetrafluoroborate in dry CH2C12 solution. The mechanism of this unexpected new nitration is also discussed.