bluuebunny/crossref_metadata_2025 huggingface dataset:
4‐Oxa(thia)‐9‐oxa‐2‐azabicyclo[4.2.1]nonane‐3‐on(thion) derivatives
Authors: Škarić Vinko , Hohnjec Marijan , Škarić Djurdjica
Published: December 2004

The synthesis of 7,8‐dihydroxy‐2‐(2‐methoxycarbonylethyl)‐4,9‐dioxa‐2‐azabicyclo[4.2.1]nonane‐ 3‐thione (16) and of its parents 9‐oxa‐4‐thia‐3‐thione 17, and 9‐oxa‐4‐thia‐3‐one 18 is described. The conversion of 5′‐deoxy‐5′‐iodo‐2′,3′‐O, O‐isopropylidene‐5,6‐dihydrouridin (1) into the 2‐O‐methyl‐5,6‐dihydrouridine 5, the 5′‐O‐acetyl‐5,6‐dihydrouridine 4, and into the N‐(5‐O‐acetyl‐2,3‐O, O‐isopropylidene‐β‐D‐ribofuranosyl)‐N‐(2‐methoxycarbonyl thyl)‐urea (6) invoked 2′,3′‐O, O‐isopropylidene‐2,5′‐anhydro‐5,6‐dihydrouridine (2) as the common intermediate.
Cyclobutanones via the (1‐Oxycyclopropyl)methanol Route
Authors: Wenkert Ernest , Golob Norman F. , Hatch Robert P. , Wenkert David , Pellicciari Roberto
Published: December 2004

A variety of alcohols of the 1‐oxycyclopropyl structure, prapared mostly from α‐alkoxy‐α,β‐unsaturated ketnnes and esters by way of reductinn and Simmons‐Smith reaction of the resultant α‐alkoxyallyl alcohols, are shown to rearrange into cyclobutanones on acid treatment (cf. Scheme 1).
Kinetik sehr schneller Methylquecksilber‐Übertragungsreaktionen zwischen pyridinhaltigen Chelatliganden und dem Hydroxid‐Ion
Authors: Geier Gerhard , Erni Isidor , Steiner René
Published: December 2004

Kinetics of very fast Methylmercury‐Transfer Reactions between Pyridine‐containing Chelating Ligands and the Hydroxide Ion

The kinetics of the reactions between methylmercury hydroxide and bipyridine, terpyridine, phenanthroline and pyridine‐2‐azo‐4‐dimethylaniline have been studied by means of the temperature jump relaxation method. These bi‐ and tridentate ligands form methylmercury chelates. Their formation is faster than the formation of the pyridine complex. The chelate complexes show an unusually high reactivity. Their reaction rates with hydroxide ions reach almost the diffusion controlled limit.
The photoenol tautomer of 5‐methyl‐1, 4‐naphthoquinone
Authors: Rommel Erika , Wirz Jakob
Published: December 2004

Irradiation of pale yellow 5‐methyl‐1, 4‐naphthoquinone (1, Scheme 1) yields the blue photoenol 4‐hydroxy‐5‐methylidene‐1(5H)‐naphthalenone (2) which is stable at 77 K. At room temperature the enol retautomerizes to starting material, the reaction rate being strongly dependent on the hydrogen‐bond‐acceptor basicity of the solvent. The enol is trapped in the presence of acid by protonation at the remaining carbonyl oxygen atom and subsequent electrophilic reaction of the exocylclic methylene group.
The Synthesis of Cycloalkenes by the Intramolecular Wittig Reaction
Authors: Becker Konrad B.
Published: December 2004

A simple synthesis of a series of bicyclo[m.n.0]‐1‐alkenes (m, n = 3,4,5) from 2‐oxocycloalkanecarboxylates by the intramolecular Wittig reaction is reported (see p. 70–72). The spectral properties (IR., 1H‐NMR. and 13C‐NMR.) of these annulated trisubstituted olefins are discussed.
Zur Kenntnis der nickel‐katalysierten Mischoligomerisation von Butadien mit Hydrazonen. Vorläufige Mitteilung
Authors: Blaser Hans‐Ulrich , Reinehr Dieter
Published: December 2004

Studies on the nickel‐catalysed reaction of butadiene with hydrazones

The nickel‐catalysed reaction of butadiene with methyl‐hydrazones yields a series of isomeric azo‐compounds identified as 2:1 adducts. The products are compared with those of the analogous reaction of butadiene with imines (cf. Scheme 1–3).
Über Pterinchemie. 60. vorläufige Mitteilung [1]. Eine neue, regiospezifische Synthese von L‐Biopterin
Authors: Schircks Bernhard , Bieri Jost H. , Viscontini Max
Published: December 2004

A new, regiospecific synthesis of L‐biopterine

Pure L‐biopterine (I) is obtained in 35–40% yield by condensation of 5‐desoxy‐L‐arabinose‐hydrazone acetate with 2,4,5‐triamino‐6‐hydroxy‐pyrimidine, followed by oxidation of the formed tetrahydro‐derivative and deacetylation of the L‐bioterine diacetate. Catalytic reduction of the L‐biopterine gives the expected mixture of two diastereomeric tetrahydro‐L‐biopterines.
Esters phosphoriques cycliques ou non cycliques de quelques O‐isopropylidène‐1,2‐α‐D‐pentofurannoses. Communication préliminaire
Authors: Tronchet Jean M. J. , Neeser Jean‐Richard , Charollais Etienne J.
Published: December 2004

Cyclic and acyclic phosphate esters of some 1,2‐O‐isopropylidene‐α‐D‐pentofuranoses

When treated with monophenyl phosphorodichloridate, 1,2‐O‐isopropylidene‐α‐D‐xylofuranose gave the two possible, isolable isomers of the corresponding 3,5‐cylic phenylphosphate. Upon phosphorylation of the same sugar derivative using bis (2,2,2‐trichloroethyl) phosphorochloridate only one isomer was formed. The same situation obtained when preparing 1,2‐O‐isopropylidene‐α‐D‐ribofuranose‐3,5‐cyclic phenylphosphate. The synthesis of a new kind of sugar phosphate with a branched‐chain unsaturated sugar moiety namely the trans‐3‐deoxy‐3‐C‐cyanomethylene‐1,2‐O‐isopropylidene‐D‐erytho‐pentofuranose 5‐bis(2,2,2‐trichloroethyl) phosphate is also described.
Carotenoids of Rhizobia. I. New Carotenoids from Rhizobium lupini
Authors: Kleinig Hans , Heumann Wolfram , Meister Walter , Englert Gerhard
Published: December 2004

The main pigments of Rhizobium lupini were 2,3,2′,3′‐di‐trans‐tetrahydroxy‐β,β‐caroten‐4‐one and 2,3,2′,3′‐di‐trans‐tetrahydroxy‐β,β‐carotene. As minor components 7,8,7′,8′‐tetrahydro‐ψ, ψ‐carotene (ζ‐carotene), β, β‐carotene (β‐carotene), and tentatively, a 2,3,2′(or 3′)‐trihydroxy‐β, β‐caroten‐4‐one and a 2,3,2′(or 3′)‐trihydroxy‐β, β‐carotene were identified.
Stereoselective in‐vitro aromatic‐ring oxygenations of chiral 1,4‐benzodiazepin‐2‐ones
Authors: Kolbah Dragutin , Blažević Nikola , Hannoun Mohammad , Kajfež Franjo , Kovač Tomislav , Rendić Slobodan , Šunjić Vitomir
Published: December 2004

Biological N(1)‐demethylation and C(3)‐hydroxylation of two enantiomeric 1,4‐benzodiazepin‐2‐ones 1 and 2 (cf. scheme 2) were found to be nonstereoselective. Aromatic‐ring hydroxylation, however, took place in the (S)‐series only, leading to 3′‐ and 4′‐hydroxylated, N(1)‐demethylated, metabolites (54 and 56, cf. scheme 5: these structures were unambiguously confirmed by comparing their UV., CD., and mass spectra with those of authentic specimens). Several compounds, theoretically conceivable as products of hydroxylation in the aromatic A‐ring of 1 and 2 by mechanisms including the NIH‐shift (cf. scheme 3), were synthesized but none of these compounds was yet isolated from in vitro incubation mixtures.
The Transmission of Polar Effects Polar Effects. Part II
Authors: Grob Cyril A. , Kaiser Ado , Schweizer Thomas
Published: December 2004

The pK values for nine acyclic, mono‐ and bicyclic α‐, β‐ and γ‐(trimethyl)ammonio acids, 1(α‐γ), 2(α‐γ) and 3(α‐γ), respectively, have been measured in 50% aqueous ethanol. The comparison of these values with those for the nine homomorphous α‐, β‐ and γ‐acids, 4(α‐γ), 5(α‐γ) and 6(α‐γ), respectively, permits an evaluation of the steric effect of the (trimethyl)ammonio groups which is super‐imposed on their polar effect in the former acids. The pK values, corrected for the steric effect, correlate very well with the reciprocal distance between the positive nitrogen atom and the dissociable proton. This confirms our earlier conclusion that the strength of these acids is determined by the field effect of the (trimethyl)ammonio groups only, the inductive model failing to account for the results. The distinction between two different transmission mechanisms for the polar effect therefore becomes unnecessary, the inductive model appearing as an atomistic description of the field effect.
13C‐ and 1H‐NMR. Studies on the Configuration of Tricarbonyliron Complexes of Oxa‐ and Aza[4.4.3]propellanes
Authors: Bachmann Kurt , Von Philipsborn Wolfgang , Amith Chaim , Ginsburg David
Published: December 2004

The configurations of a series of mono‐ and bis‐Fe(CO)3 complexes of 12‐oxa[4.4.3]‐propella‐2,4,7,9‐tetraene (1) and of 11,13‐dioxo‐12‐methyl‐12‐aza[4.4.3]propella‐2,4,7,9‐tetraene (7) as well as of a trienic aza‐propellane complex have been studied in solution by 13C‐ and 1H‐NMR. spectroscopy. Praseodymium‐induced 13C‐shifts of the metalcarbonyl carbon atoms and of the central carbon atom of the complexed diene systems are particularly sensitive and useful to prove exo‐ or endo‐configuration of the tricarbonyliron ligand. In addition, H,H‐ and C,H‐coupling constants of the complexes and parent compounds are reported and discussed.
The Electronic States of the Pentatetraene Radical Cation
Authors: Bieri Gerhard , Dill James D. , Heilbronner Edgar , Maier John P. , Ripoll Jean L.
Published: December 2004

HeIα excited photoelectron spectra of pentatetraene and the inferred ionization energies are reported. The first band has a characteristic Franck‐Condon envelope similar to the first photoelectron bands of allene and butatriene. The four bands found below 16 eV ionization energy have been assigned to the X̃2E, Ã2E, B̃2E and C̃2B2 states of the radical cation of pentatetraene by comparison with STO‐3G and SPINDO calculations on the cumulene series. The correlation scheme includes the 2s shell ionization energies of ethylene, allene and butatriene. The π‐orbital ionization trends of the cumulenes are discussed in the framework of localized orbitals calculated with the STO‐3G basis set.
Totalsynthese von Betalainen
Authors: Hermann Kurt
Published: December 2004

Total Synthesis of Betalaines

cis‐4‐Oxo‐2,6‐piperidinedicarboxylic acid dimethyl ester (10) was transformed (44%) into the semicarbazone of 2,3‐dihydrobetalamic acid dimethyl ester (13/14) by a modified Horner‐Wittig reagent 12. Oxidation of 13/14 afforded 41% of a mixture of stereoisomers of betalamic‐acid‐dimethyl‐ester semicarbazone (4), key intermediate for the synthesis of betalaine pigments. The utility of 4 in this respect was demonstrated on a small scale by its conversion to the dimethyl ester of indicaxanthine (9, 11%) and to the trimethyl ester of betanidine (7, 87%). Hydrolysis of 7 gave betanidine (6).

We further describe the synthesis of the trimethyl ester of an oxidized form of betalamic acid (20/21) as well as model condensation reactions on the carbonyl group of cyclohexanone, cis‐4‐oxo‐2,6‐diphenylpiperidine (23) and its N‐formyl derivative 27.

Reaction of 4‐oxo‐1,2,3,4‐tetrahydro‐2,6‐pyridinedicarboxylic‐acid dimethyl ester (40) with acetic anhydride or with triethyloxonium tetrafluoroborate resulted in O‐acylation or in O‐alkylation along with dehydrogenative aromatization to yield the derivatives 39 or 42, respectively, of chelidamic acid.
Photochemische Reaktionen. 93. Mitteilung. Zur Photochemie konjugierter Epoxy‐inone: Die UV.‐Bestrahlung von 5,6‐Epoxy‐5‐isopropyl‐6‐methyl‐hept‐3‐in‐2‐on
Authors: Eichenberger Herbert , Wolf Hans Richard , Jeger Oskar
Published: December 2004

The Photochemistry of Conjugated Epoxy‐Inones: Photolysis of 5,6‐Epoxy‐5‐isopropyl‐6‐methyl‐hept‐3‐in‐2‐on

This paper continues the series of investigations of the photochemistry of α,β‐unsaturated γ,δ‐epoxyketones by examining the hitherto unknown photochemical behaviour of α,β‐acetylenic‐γ,δ‐epoxy‐ketones. As model compound, the aliphatic epoxy‐ynone 7 (thermally stable at 180°) was synthesized (Scheme 1). It can be converted with BF3O (C2H5)2 in good yields to the 1,5‐diketone 8, the yne‐1,4‐diketone 49 and in small amounts to the fluorhydrine 50 (Scheme 1).

On n,π*‐ or π, π*‐excitation, 7 shows mainly cleavage of the C (γ)‐O‐bond to give a diradical a (Scheme 11), whose ultimate fate is strongly solvent dependent. In acetonitrile a mainly rearranges to the 1,5‐diketone 8 and, to a smaller extent, shows fragmentation to acetone and formation of polymers. Except for small amounts of the dimeric products 9A,9B and biphenyl, the same compounds are obtained in benzene. In cyclopentane, however, a gives only little of 8, and mainly a plethora of compounds formed by a radical process like H‐abstraction from solvent, incorporation of cyclopentylradicals, dimerization and fragmentation reactions (9A, 9B, 11–20) (Scheme 3). Irradiation of 7 in propan‐2‐ol or in dioxane yields products of analogous radical processes as well of photoreduction (Scheme 4). However, the analogous epoxyenone 32 gives mainly products of photoisomerizations without interference by the solvent [6].

On photochemical excitation in acetonitrile, the 1,5‐diketone 8 shows unspecific decomposition, but in cyclopentane it yields the reduction products 12, 26A, 26B, 27, 28 plus cyclopentylcyclopentane (15) (Scheme 6).
1H‐NMR.‐, 13C‐NMR.‐, UV.‐ und CD.‐Daten von synthetischem (3S, 3′S)‐Astaxanthin, seinem 15‐cis‐Isomeren und einigen analogen Verbindungen
Authors: Englert Gerhard , Kienzle Frank , Noack Klaus
Published: December 2004

1H‐NMR., 13C‐NMR., UV. and CD. spectral data of synthetic (3S, 3′S)‐astaxanthin, its 15‐cis isomer, and some related compounds

1H‐NMR., 13C‐NMR., UV. and CD. spectra are reported for synthetic (3S, 3′S)‐astaxanthin (1), its 15‐cis isomer (2), its diacetate (3), and the 15, 15′‐didehydro compound (5). These data prove the identity of the synthetic and the naturally occuring compound 1. A full interpretation of the 1H‐ and 13C‐NMR. spectra is given and confirms the configuration of all the double bonds. The conformation of the cyclohexene end group of all the compounds is shown to be identical. The signs of the different CD. maxima of 15‐cis‐astaxanthin are found to be opposite to those of the all‐trans compound.
Isomerization of the Radical Anions of 6a‐Thiathiophthenes
Authors: Gerson Fabian , Gleiter Rolf , Ohya‐Nishiguchi Hiroaki
Published: December 2004

The radical anions of 6a‐thiathiophthenes ([1,2]dithiolo[1,5‐b] [1,2]dithioles), I(R), convert into those of 4H‐thiapyran‐4‐thiones, III(R), via cis‐trans isomerization. The reaction is slowed down when the size of the substituent R in the 2,5‐positions of 6a‐thiathiophthene increases, and it is prevented by the introduction of a 3,4‐polymethylene bridge. The primary and the secondary radical anions, I(R)\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document} and III(R)\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, respectively, exhibit very similar hyperfine splitting patterns. E.g., in the case of the unsubstituted 6a‐thiathiophthene, I(H), and 4H‐thiapyran‐4‐thione, III(H), the proton coupling constants are aH2,5=6.72 and aH3,4=1.73 Gauss for I(H)\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, and aH2,6=6.35 and aH3,5=2.07 Gauss for III(H)\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. In contrast to I(H)\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, cis‐trans isomerization could not thus far be proved to occur with its 1,6‐dioxa‐analogue, IV(H)\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, since no ESR. spectrum of the radical anion of 4H‐pyran‐4‐thione, V(H), was detected upon reduction of IV(H).
The ESR. Spectrum of the Diphenylcyclopropenone Radical Anion
Authors: Fürderer Peter , Gerson Fabian , Krebs Adolf
Published: December 2004

The ESR. spectrum of the relatively unstable radical anion of diphenylcyclo‐propenone (II) has been observed upon electrolytic reduction of II in N,N‐di‐methylformamide and 1,2‐dimethoxyethane. Simple MO models account well for the π‐spin distribution and for the restricted rotation of the phenyl substituents in II\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. A rather facile loss of a CO molecule by II\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document} results in formation of the radical anion of tolane (diphenylacetylene; III). No ESR. spectra could be obtained for the radical anions of dialkylcyclopropenones which are even shorter‐lived than II\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, although decay by decarbonylation seems to be less favoured with them than with II\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. In presence of air, electrolytic reduction of either II or its dimethyl and di‐t‐butyl analogues yields the correspondingly disubstituted semidione anions.
Einbauversuche mit (3H und 14C)‐doppelmarkiertem Farnesol in Cantharidin. 5. Mitteilung zur Biosynthese des Cantharidins
Authors: Peter Martin G. , Waespe Hans‐Rudolf , Woggon Wolf‐Dietrich , Schmid Hans
Published: December 2004

Incorporation experiments with (3H and 14C) doubly labelled farnesols into cantharidin

After injection of 11′, 12‐[3H]‐7‐[14C]‐farnesol or 11′, 12‐[3H]‐5,6‐[14C]‐farnesol, the 3H‐label is located specifically in the C(9)‐methyl‐group of cantharidin, whereas the 14C‐labelling pattern follows an incorporation via acetic acid (Scheme 4). C‐Atoms 5, 6 and 7 from the middle part of the farnesol molecule are utilized for cantharidin biosynthesis to an extent that is about 2.1–11% of the incorporation rate of the methyl groups C(11′) and C(12), depending on the position of the 14C‐label in farnesol. These results confirm our earlier hypothesis [1] that the C10‐molecule cantharidin is biosynthesized from the C15‐precursor farnesol which is cleaved between C(1)–C(2), C(4)–C(5), and C(7)–C(8). The synthesis of 7‐[14C]‐farnesol and of 5,6‐[14C]‐farnesol is described.
Synthese und NMR.‐Spektren von neuartigen Lanthanoid‐Kobalt‐Sandwichkomplexen
Authors: Kläui Wolfgang
Published: December 2004

Synthesis and NMR. Spectra of Novel Lanthanide‐Cobalt Sandwich Compounds

The reaction of [(C5H5)Co{P(O)(OR)2}2{P(OH)(OR)2}] (3, R = CH3, C2H5) with lanthanide(III) compounds yields the cationic trinuclear complexes [{(C5H5)Co[P(O)(OR)2]3}2Ln]⊕X⊖ (2, R = CH3, C2H5; Ln = La, Eu, Pr; X = BF4, BPh4). According to thermogravimetric and NMR. studies these compounds do not contain additional coordinated water molecules. It is therefore supposed that the central lanthanide ion has a regular sixfold coordination of phosphoryl ligands. The 31P‐ and 1H‐NMR. spectra of 2 (R = CH3; Ln = La, Eu, Pr) and 3 are discussed. It can be shown that the Fermi contact shift as well as the coordination shift make significant contributions to the observed lanthanide induced shift of the cyclopentadienyl signal.The dominating influence of the Fermi contact interaction on the 31P chemical shift is in accord with theoretical considerations and comparable experimental values. The temperature dependence of the proton chemical shifts of 2 (R = CH3; Ln = Eu) is also discussed.
Contribution à la phytochimie du genre Gentiana, XX. Identification de nouveaux di‐O‐glucosides de C‐glucosylflavones dans Gentiana asclepiadeaL.
Authors: Goetz Michel , Jacot‐Guillarmod André
Published: December 2004

Phytochemistry of genus Gentiana, XX. Identification of new di‐O‐glucosides of C‐glucosylflavones in Gentiana asclepiadea L.

Two new O‐glucosides of C‐glucoside flavonic compounds [isoorientin‐2″,4′‐di‐O‐β‐D‐glucoside (1) and isovitexin‐2″‐4′‐O‐β‐D‐glucoside (2)] have been isolated from leaves of Gentiana asclepiadea L. This is the first case of di‐O‐glucosides of C‐glucoside flavones occurring in nature.
Ircinianin, a Novel Sesterterpene from a Marine Sponge
Authors: Hofheinz Werner , Schönholzer Peter
Published: December 2004

Ircinianin (2), a new furano‐sesterterpenetertronic acid, has been isolated from a marine sponge of the genus Ircinia. Structure 2 has been established by X‐ray diffraction methods.
Homoisoflavanones. V. Crystal and Molecular Structure of (−)‐7‐O,‐(p‐Bromophenacyl)‐eucomol. The Absolute Configuration of (−)‐Eucomol
Authors: Weber Hans Peter , Heller Werner , Tamm Christoph
Published: December 2004

Homoisoflavanone. V. Kristalline und molekulare Struktur von (−)‐7‐O,‐(p‐Bromphenacyl)‐eucomol. Absolute Konfiguration von (−)‐Eucomol

Zur Abklärung der absoluten Konfiguration von (−)‐Eucomol wurde eine Röntgenstrukturanalyse des 7‐O‐p‐Bromphenacylderivates durchgeführt. Auf Grund der anomalen Streuung von CuKα‐Strahlung durch Brom liess sich 3S‐Chiralität der Verbindung nachweisen. Die durch 372 Atomparameter beschriebene Struktur wurde mit 1745 Strukturfaktoren bis zu R = 0,071 verfeinert.
Synthesis and structure of fluorotricyanomethane
Authors: Britton Doyle , Farooq Saleem , Keese Reinhart
Published: December 2004

Fluorotricyanomethane is prepared from potassium tricyanomethanide and perchlorylfluoride. The crystal structure of this compound (orthorhombic, space group P212121, with a=6.270, b=6.734, c=11.776 Å) has been determined by X‐ray analysis. The results are discussed in relation to those of (NC)3CX (X=CH3, Cl, Br or CN).
The Crystal and Molecular Structure of Hydroxybenzylpindolol
Authors: Weber Hans Peter , Petcher Trevor J.
Published: December 2004

Kristalline und molekulare Struktur von Hydroxybenzylpindolol

Im Zusammenhang mit einer Studie über die Konformation von adrenergen β‐Blockern wurde die kristalline Struktur von Hydroxybenzylpindolol durch Röntgen‐analyse bestimmt. Die Kristalle sind triklin, Raumgruppe P1, a = 10,041(2), b = 11,386(2), c = 10,131(2) Å, α = 114,03(2), β = 107,82(3), γ = 99,32(3)°, mit zwei Molekeln pro Zelle. Die Struktur wurde nach dem «Multisolution»‐Prinzip gelöst und bis zu R=0,050 verfeinert. Die Molekeln sind im Kristall durch ein Netz von Wassertoffbrücken miteinander verbunden.
Reactions of 1,3,5,7‐Tetramethyl‐anti‐tricyclo[5.1.0.03,5] octane‐2,6‐diols and their 4,4,8,8‐Tetrachloro‐ and 4,8‐Dichloro‐Derivatives with Diphosphorus Tetraiodide
Authors: Dyllick‐Brenzinger Rainer , Oth Jean F. M. , Chapleo Christopher B. , Dreiding André S.
Published: December 2004

Reaktionen von 1,3,5,7‐Tetramethyl‐anti‐tricyclo[5.1.0.03,5]octan‐2,6‐diolen und deren 4,4,8,8‐Tetrachlor‐ und 4,8‐Dichlorderivaten mit Diphosphortetrajodid

Es wurden die P2I4‐Reaktionen mit 1,3,5,7‐Tetramethyl‐anti‐tricyclo[5.1.0.03,5]‐octan‐2,6‐diolen (3/6), mit dem 4,8‐Dichlorderivat 4 und mit den 4,4,8,8‐Tetrachlorderivaten 5/7 untersucht. Dabei entstanden die Styrolderivate 9 und 12, die anti‐Bishomobenzolderivate 8 und 11, ein Homotropylidenderivat 10, ein Cyclo‐octatetraenderivat 13 und ein 9‐Oxabicyclo[4.2.1]nona‐2,4,7‐trienderivat 15. Die Ausbeuten lagen zwischen 1 und 10%. Die Bildung aller dieser Produkte liess sich unter der Annahme der primären Umwandlung einer oder beider Hydroxylgruppen in Abgangsgruppen X oder X und Y (wahrscheinlich X=Y=I) mechanistisch deuten. Die Reaktion der Deschlorderivate 3/6 lieferte nach Substitution beider Hydroxyl‐gruppen durch X und Y: (a) unter Abspaltung von HX und HY das Styrolderivat 9 (Schema 2) und (b) unter Abspaltung von XY das Homotropylidenderivat 10 (Schema 3a) und das Bishomobenzolderivat 8 (Schema 3b). Die Reaktion des 4,8‐Dichlor‐derivates 4 lieferte nach Substitution beider Hydroxylgruppen durch X und Y: (a) unter Abspaltung von HX und HY das Styrolderivat 12 (Schema 2), und (b) unter Abspaltung von XY das Bishomobenzolderivat 11 (Schema 3b). Die Reaktion mit den 4,4,8,8‐Tetrachlorderivaten 5/7 lieferte: (a) nach Substitution beider Hydroxyl‐gruppen durch X und Y unter Abspaltung von XCl und YCl das Cyclooctatetraen‐derivat 13 (Schema 4), und (b) nach Substitution nur einer Hydroxylgruppe durch X unter Abspaltung von XCl und HCl das bicyclische Derivat 15 (Schema 5). Alle diese Reaktionen sind zusätzlich zu den angegebenen Fragmentierungen und Eliminierungen noch teilweise von Umlagerungen des Kohlenstoffgerüstes begleitet.

Die thermische Umlagerung von 1,5‐Dichlor‐2,4,6,8‐tetramethyl‐cycloocta‐1,3,5,7‐tetraen (13) in das Styrolderivat 12 wurde in Abhängigkeit der Lösungs‐mittelpolarität untersucht und mit der analogen thermischen Umlagerung von Brom‐cyclooctatetraen und Chlor‐cyclooctatetraen verglichen.
Verrucarin K, the First Natural Trichothecene Derivative Lacking the 12,13‐Epoxy Group. Verrucarins and Roridins. 34th Communication [1]
Authors: Breitenstein Werner , Tamm Christoph
Published: December 2004

A new metabolite, verrucarin K (C27H34O8) has been isolated from a strain of Myrothecium verrucaria (ALBERTINI et SCHWEINITZ) DITMAR ex FRIES. On the basis of spectral and chemical evidence structure 1 was assigned to the new compound. Base‐catalysed hydrolysis yielded verrucarinolactone (5), E,Z‐muconic acid (6) and trichotheca‐9, 12‐diene‐4,15‐diol (3). The implications of 1 in the trichothecane biosynthesis are discussed.
Synthesis and X‐Ray Analysis of 2‐(2‐2H‐benzotriazolyl)‐N‐(6‐quinoxalinyl)aniline, the Rearrangement Product from 1,2‐Bis(2‐aminophenylazo)benzene and Glyoxal. Macrocyclic Aza Compounds. IV
Authors: Luger Peter , Malkowski Jerzy , Skrabal Peter
Published: December 2004

The title compound 2 was synthesized from the intermediates 3 and 4. It is identical with the rearrangement product of 1 and glyoxal, of which the X‐ray structure analysis is described.
Acid‐Catalysed Dehydration of Tricyclic Unsaturated Alcohols
Authors: Hayakawa Kenji , Schmid Hans
Published: December 2004

The tricyclic alcohols 3–7, derived from the corresponding ketones 1 and 2 (Scheme 1), by action of acids underwent dehydration with skeletal rearrangements. Dehydration of 3 and 4 with POCl3/pyridine (procedure A) afforded the polycyclic hydrocarbons 9, 10, and 12, 13, respectively. With TsOH (procedure B), on the other hand, 3 and 4 gave homo‐triquinacenes 10 and 14 respectively, as well as the polycyclic ethers 11 and 15 (Scheme 2). Hydrocarbon 9 (or 12) was converted into 10 FSO3H to the tertiary alcohol 16 (Scheme 4). Plausible mechanisms for these transformations are summarized in Scheme 8. Dehydration of the secondary alcohols 5 and 7 was effected by procedure A. While treatment of alcohol 5 with POCl3/pyridine yielded two isomeric hydrocarbons 17 and 18, similar dehydration of its epimeric alcohol 7 afforded hydrocarbon 21 as the sole product. The tertiary alcohol 6 was dehydrated by both procedures to yield two isomeric hydrocarbons 19 and 20 (Scheme 5). Hydrocarbon 20 was converted into 19 by procedure B (mechanisms, Scheme 10). Reaction of ketone 2 with CF3COOH gave the addition product 22 converted into vinylsulfonyl fluorides 24 and 25 by treatment with FSO3H (Scheme 6). Homo‐triquinacenes 10 and 14 reacted smoothly with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione to give the ‘ene’‐reaction products 26 and 27, respectively.
Über Reaktionen oxygenierter Kobalt(II)‐Komplexe. IX. Oxydative Eigenschaften von Tetrakis(äthylendiamin)‐μ‐peroxo‐μ‐hydroxo‐dikobalt(III)
Authors: Brüstlein‐Banks Pauline , Fallab Silvio
Published: December 2004

Reactions of oxygenated cobalt(II) complexes. IX. Oxidative properties of tetrakis(ethylenediamine)‐μ‐peroxo‐μ‐hydroxo‐dicobalt(III)

VIII s. [1].

[(en)2Co(O2, OH)Co(en)2]3+ (a) reacts with I− in acidic aqueous solution according to: CoIII(O2, OH)CoIII + 21− + 5H+ ⇀ 2CoIII + 3H2O + I2. Using I− in excess first order rate constants are obtained which, to a first approximation, are independent of [I−]. Comparison with kinetic data of deoxygenation of [(en)2Co(O2, OH)Co(en)2]3+ under analogous conditions suggests that both reactions have the same rate determining step. The singly bridged species [(en)2(H2O)CoO2Co(H2O) (en)2]4+ is shown to be the reactive intermediate in the iodide oxidation (Schema 2).
Stereospecific Formation of Pentaamine Complexes of Co(III) with Terdentate 2,6‐Bis(aminomethyl)pyridine
Authors: Tinner Ursula , Marty Werner
Published: December 2004

Some pentaamine complexes of Co(III) with 2,6‐bis(aminomethyl)pyridine (bamp), a diamine ligand (or two ammonia ligands) and one unidentate ligand have been prepared (Table 1). In all these species, bamp remains coordinated meridionally under a variety of conditions as shown by 1H‐ and 13C‐NMR. spectroscopy and correlations by stereoretentive reaction cycles. The rates of amine proton exchange and of spontaneous aquation, Hg2+‐induced aquation and base hydrolysis of some chloropentaamine complexes have been determined. They essentially follow the patterns observed for complexes with purely aliphatic amine ligands; the presence of a pyridine donor in these complexes does not suggest deviations from the mechanistic schemes usually proposed for the solvolytic reactions investigated.
The Ionization Energies of Di‐n‐Alkyl Diacetylenes
Authors: Heilbronner Edgar , Jones Taylor B. , Maier John P.
Published: December 2004

The He(Iα) photoelectron spectra and the ionization energies of symmetrically substituted di‐n‐alkyl‐diacetylenes R‐(CC)2‐R (with R  CH3, C2H5, n‐C3H7, n‐C4H9) are presented. The effect of the alkyl substitutents is that the two acetylenic ionization energies, Iv,1 and Iv,2, shift by the same amount, i.e. their difference Iv,2 – Iv,1 remains constant (2.45 ± 0.05 eV). Between 12.5 eV and 17 eV the band system in the photoelectron spectrum of R‐(CC)2‐R is superimposable with that in the spectrum of the corresponding alkane, RH, with the exception of a uniformly small shift of all the bands to higher ionization energy.
Die Carotinoide der Blüten von Rosa foetida
Authors: Buchecker Richard , Eugster Conrad Hans
Published: December 2004

Carotenoids in petals of Rosa foetida

The petals of Rosa foetida, HERRM., a species of prime importance in the history of breeding true yellow garden roses, have been analysed for carotenoids for the first time. The following components were identified: β‐carotene (1, 4,5%), lutein (2, 8%), zeaxanthin (3, 17,4%), auroxanthin (4, 30,8%), luteoxanthin (5, 21,9%), violaxanthin (6, 9,2%) and neochrome (7, 4,1%). Not identified carotenoids (4,1%) contained probably mutatoxanthin, antheraxanthin and apocarotenals. Thus the brillant yellow colour of R. foetida flowers is due mainly to carotenoid epoxides.
Säurekatalysierte Umlagerungen von 1,5‐Dimethyl‐6‐methyliden‐tricyclo[3.2.1.02,7]oct‐3‐en‐8endo‐olen
Authors: Mukherjee‐Müller Gabriele , Gilgen Paul , Zsindely Janos , Schmid Hans
Published: December 2004

Acid Catalysed Rearrangement of 1,5‐Dimethyl‐6‐methyliden‐tricyclo[3.2.1.02,7]oct‐3‐en‐8endo‐ols

The tricyclic alcohols 2,3,4 and 6 (Scheme 1) are synthesized by the reaction of the tricyclic ketone 1 with sodiumborohydrid or metalloorganic reagents. Their configuration at C(8) is determined by NMR. in the presence of Eu(fod)3. The exo‐attack of 1 by the nucleophil forming the endo‐alcohol is favored, the π‐electrons of C(3) = C(4) hindering the endo‐attack. On treatment with sulfuric acid in dioxane/water at 25° the tertiary alcohols yield aryl‐substituted ketones. 3 gives in 78.5% yield a mixture of the 3‐(dimethylphenyl)‐2‐butanones 12 and 13, in addition to 16.5% of (2,3,4‐trimethylphenyl)‐2‐propanon (14) (Scheme 2). The alcohols 4 and 6 yield mixtures of the 2‐(dimethylphenyl)‐3‐pentanones 19 and 20 (72%), and 2‐(dimethylphenyl)‐propiophenones 21 and 22 (68%), respectively (Scheme 2). In the case of the secondary alcohol 2 mainly products derived from hydration at the C(6), C(9) double bond are formed, namely the mixture of diols 23 and 24 (21%), and the mixture of the isomeric 2‐(dimethylphenyl)propanals 25, 26 and 27 (3%) (Scheme 3). ‐ The structures of 12–14, 19/20, 21/22, 23/24 and 25/26/27 were established by spectroscopic data. In the case of 12 and 13 the degradation of their mixture to the known 1‐(dimethylphenyl)ethanols 17/18 confirmed the assignment. ‐ The most probable mechanism for the rearrangement of 3 is shown in Schemes 4 and 5. The reaction proceeds from 3 through a, b and g to 12 and 13; 14 is formed via e, f and i. In the case of 4 and 6 only the reaction analogue to 3 → a → b → g ⇉12/13 takes place. The isomeric aldehyds 25–27 formed from 2 could have the structures s, t, and v. The former two could be generated in a similar way as 12/13 from 3, the latter one as shown in Scheme 8.
Crystal Structure of Metal‐Ion Complexes with neutral noncyclic Ionophores
Authors: Neupert‐Laves Katarina , Dobler Max
Published: December 2004

Crystal structure determinations of two metal‐ion complexes with noncyclic ionophores are reported: (i) CaCl2 complex of N,N,N′,N′‐Tetrapropyl‐3,6‐dioxa‐octane diamide, space group Fddd, a = 14.659, b = 19.616, c = 33.173 Å; (ii) MnBr2 complex of N,N,N′,N′‐Tetrapropyl‐1,2‐cyclohexylenedioxydiacetamide, space group I4, a = b = 11.695, c = 21.299 Å.
Nucleophilicity and Basicity in the Quaternization of 4‐Substituted Quinuclidines. Polar effects. Part III
Authors: Grob Cyril A. , Schlageter Markus G.
Published: December 2004

The second order rate constants (k) for quaternization of thirty 4‐substituted quinuclidines (1) by methyl iodide in methanol have been measured. The effects of the substituents on rate are relatively small and indicate an early transition state with little charge separation. They also indicate less involvement of the nitrogen atom,i.e.a looser transition state, for quaternization by allyl halides than for the less reactive propyl halides. The logkvalues of 4‐substituted quinuclidines correlate moderately well with their pKavalues, the main reason being the imperfect correlation between nucleophilicity and basicity. The assumption that substituents exert equal effects on rates and equilibria is therefore only partly justified. Certain irregularities in the correlation can be attributed to a reduction of the nucleophilicity of nitrogen in1due to hydrogen bonding to the solvent methanol. Furthermore, quaternization is faster and responds more strongly to substituent effects in the aprotic solvent acetonitrile.
Nucleophilic Additions to Unactivated Carbon‐Carbon Double Bonds. Base‐Catalysed Ether Formation. Preliminary Communication
Authors: Ammann Willi , Ganter Camille
Published: December 2004

Several examples (3 → 5, 4 → 7, 6 → 7, 9 → 10) of base‐catalysed intramolecular ether formation involving nucleophilic attack on an unactivated carbon‐carbon double bond are described.
Reactions of Tricyclic Vinylcyclopropanes with Metal Carbonyls
Authors: Hayakawa Kenji , Schmid Hans
Published: December 2004

Irradiation of the tricyclic vinylcyclopropane 3 and Fe(CO)5 resulted in the formation of the s̀,π‐bonded iron complex 7 and the π,π‐bonded iron complex 8 (Scheme 2). Complex 8 was easily degraded with silica gel to give hydrocarbon 9, which reproduced 8 by photolysis in the presence of Fe(CO)5. Photolysis of 7 afforded a mixture of 3 (23%), 9 (27,5%), and three other hydrocarbons. Oxidative degradation of 7 with ceric ammonium nitrate in methanol gave the dimethoxy‐hydrocarbon 10. ‐ The tricyclic hydrocarbon 3 isomerized thermally to the bicyclic hydrocarbon 11 (with CH3C(9) in an exo position) via a homosigmatropic [1,5]‐H‐shift. On the other hand, 3 was converted into the other isomer 14 (with CH3C(9) in an endo position) by action of Mo(CO)6 or TsOH. Both isomers 11 and 14 reacted with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione to give the isomeric Diels‐Alder adducts 12 and 15, respectively, which were photochemically converted into the cage compounds 13 and 16, respectively (Scheme 3). ‐ Photochemical reaction of the tricyclic vinylcyclopropane 6 with Fe(CO)5 gave the σ,π‐bonded iron complexes 17 and 18. Heating of 17 at 80° resulted in a loss of one mol of carbon monoxide to give 18 in quantitative yield. Oxidative degradation of 17 with ceric ammonium nitrate in ethanol afforded the polycyclic lactones 19 and 20 by a novel type of reaction (Scheme 4). ‐ The tricyclic ketone 21 was thermally converted into the α,β‐unsaturated ketone 22 via a homosigmatropic [1,5]‐H‐shift. The configuration at C(7) of 22 was confirmed to be same as that of 11 (CH3C(9) in an exo position) by chemical conversions: 22 was reduced with NaBH4 to alcohol 23 which, in turn, was dehydrated with POCl3/pyridine to 11 (Scheme 5). Reaction of ketone 21 with Mo(CO)6 gave the α,β‐unsaturated ketone 25 and a cage compound X, whose structure was not fully elucidated. ‐ Reaction of the polycyclic epoxide 26 with Fe2(CO)9 or Mo(CO)6 yielded the allyl alcohol 27 in a novel type of reaction. The epoxides 29 and 32 were similarly converted into the corresponding allyl alcohols 30 and 33, respectively (Scheme 6).
Oxiranylmethyl‐Fragmentierung zur Bildung von Cyclopentadecan‐1,5‐dion‐Derivaten. Eine Musconsynthese
Authors: Gray Robert W. , Dreiding André S.
Published: December 2004

The Formation of Cyclopentadecane‐1,5‐dione Derivatives by an Oxiranylmethyl Fragmentation. A Synthesis of Muscone

A new method for the preparation of cyclopentadecane‐1,5‐dione (11) and its 3‐methylderivative 12, compounds with a musk fragrance, is described. Starting from the readily available bicyclic enones 9 and 10, the epoxy‐p‐toluenesulfonate 15 and its methylderivatives 20A and 20B were prepared by reduction with diisobutyl‐aluminium hydride or sodium borohydride (to 13 and 18A, 18B), epoxidation with m‐chloroperbenzoic acid (to 14 and 19A, 19B), followed by tosylation. Heating of 15 and 20A or 20B with calcium carbonate in water/dioxane under reflux caused fragmentation leading to the diketones 11 and 12 in high yields. The same fragmentation also occurred with sodium hydrogencarbonate in dimethylsulfoxide at 160°, but in lower yields. The conversion of 12 into rac‐muscone (2) was accomplished by developing a method for selectively forming the monotosylhydrazone 27. The latter was reduced with sodium borohydride and the crude alcohol 28 oxidized to 2.

Unexpectedly the pyrolysis of the epoxy‐acetate 29 at 350° in a sealed glass tube led to the bicyclic ketone 10. Treatment of 3‐methylcyclopentadecane‐1,5‐dione (12) with peracetic acid and boron trifluoride etherate gave the stable crystalline ozonide 33.
Un nouvel analogue synthétique de l'adénosine: La désoxy‐3′‐C‐dibromométhylidène‐3′‐adénosine
Authors: Tronchet Jean M. J. , Schwarzenbach Dominique
Published: December 2004

A novel synthetic analog of adenosine: the 3′‐deoxy‐3′‐C‐dibromomenthylidene‐adenosine

The title compound (7) has been prepared by a sequence of classical synthetic steps from 3‐deoxy‐3‐C‐dibromomethylidene‐1,2: 5,6‐di‐O‐isopropylidene‐α‐D‐ribo‐hexofuranose (1). The β‐configuration of the nucleoside was established by formation of a cyclonucleoside. 7 is very slowly deaminated by adenosine deaminase. In contrast with its dichloro analog, it does not inhibit the growth of Escherichia coli.
Contribution à la phytochimie du genre Gentiana XXI; Les cinnamoyl‐C‐glucosylflavones et leurs O‐glucosides dans Gentiana punctataL.
Authors: Luong Minh Duc , Jacot‐Guillarmod André
Published: December 2004

Phytochemistry of genus Gentiana XXI: The cinnamoyl‐C‐glucosylflavones and their O‐glucosides in Gentiana punctata L.

Three new (1–3) and three previously identified (4–6) cinnamoyl‐C‐glucosyl‐flavones have been isolated from the leaves of Gentiana punctata L. The structures of the new compounds were established as: trans‐cafeoyl‐2″‐iso‐orientin‐4′‐O‐β‐D‐glucoside (1), trans‐feruloyl‐2″‐isovitexin‐4′‐O‐β‐D‐glucoside (2) and trans‐feruloyl‐2″‐isovitexin (3). Isoscoparine (8) and O‐β‐D‐glucosyl‐2″‐iso‐orientin (7) were also isolated and identified.
Der Stoffwechsel von Verbindungen mit Dreifachbindung. VII. Verteilung und Abbau der 9‐Octadecinsäure bei Ratten, ein Beitrag zur α‐Oxydation der C‐Kette
Authors: Reichlmeier Klaus , Graf Peter , Kaempf Ekkehard , Bernhard Karl
Published: December 2004

Distribution and Metabolism of Octadec‐9‐ynoic acid in Rats

Octadec‐9‐ynoic acid (stearolic acid) fed to rats leads to the metabolic excretion of six dicarboxylic acids with retained triple bond. The main metabolic steps are ω‐, β‐, and presumably α‐oxidation. Feeding of 14C‐stearolic acid proves that the α‐oxidative steps involves the methyl end of the original acid. It could further be shown that this acid is incorporated partially in the body lipids. To a substantial degree it is totally oxidized and expired as 14CCO2.
A Simple Equivalent Bond Orbital Model for the Rationalization of the C2s‐Photoelectron Spectra of the Higher n‐Alkanes, in Particular of Polyethylene
Authors: Heilbronner Edgar
Published: December 2004

The higher homologues of n‐alkanes H(CH2)NH with N > ∽ 13 yield photoelectron spectra in which the C2s‐bands merge to form a double humped, unresolved C2s‐band system in the interval of I=15 to 25 eV [1]. It is shown that with the help of an equivalent bond orbital model one can derive a closed formula, which gives the individual C2s‐band positions I=−εj in function of N and j with sufficient accuracy, assuming the validity of Koopmans' approximation. The calculated I values (j=1 to N) folded with an appropriate shape function for the individual C2s‐bands reproduce the observed Franck‐Condon envelope of the C2s‐band system within narrow limits of error. However, a comparison of the observed total width of the C2s‐band system with the computed one, indicate that for large n‐alkanes (N≥ ∽ 13), the simplification which consists of taking into account only the interaction matrix elements between vicinal bond orbitals [2], is no longer a satisfactory one.
Experimente zum kompetitiven Einbau der Stereoisomeren des Farnesols in Cantharidin. 6. Mitteilung zur Biosynthese des Cantharidins
Authors: Woggon Wolf‐Dietrich , Peter Martin G. , Schmid Hans
Published: December 2004

Experiments on the competitive incorporation of farnesol‐stereoisomers into cantharidin

Farnesol (2) has been demonstrated to be an efficient precursor for cantharidin (1), into which it is transformed by elimination of C(1), C(5), C(6), C(7) and C(7′) [1]. The following incorporation experiments with doubly labelled (3H and 14C) stereoisomers of farnesol present strong evidence that (E,E)‐ farnesol ((E,E)‐2) in fact is the precursor for cantharidin, whereas (2E, 6Z)‐2 and (Z,Z)‐2 are not utilized for the biosynthesis of cantharidin. A possible mechanism for the incorporation of (2Z,6E)‐farnesol ((2Z,6E)‐2) to an extent of 56,8% relative to (E,E)‐2 is discussed.
Über Pterinchemie. 64. Mitteilung. Die Kristallstruktur von 6‐Methyl‐7,8‐dihydropterin‐monohydrochlorid‐monohydrat
Authors: Bieri Jost H.
Published: December 2004

The crystal structure of 6‐methyl‐7,8‐dihydropterine‐monohydrochloride‐monohydrate

The crystal structure of the title compound has been determined by X‐ray analysis (direct methods) and refined with 990 structure amplitudes to R = 0.025. The crystal system is triclinic, space group P1, with unit cell dimensions a = 5.859, b = 7.686, c = 12.107, α = 71.84, β = 76.35, γ = 85.80. The molecule is protonated at the N(5)‐position and is planar. The atoms H(19) and H(20) are with 0.818 Å above respectively with −0.705 Å under the plane.
Ionophore für Li+: Membranselektivität, Darstellung und Stabilitätskonstanten in Äthanol
Authors: Kirsch Norbert N. L. , Funck Robert J. J. , Pretsch Ernö , Simon Wilhelm
Published: December 2004

Membrane Selectivity and Syntheses of Ionophores for Li+. Stability Constants in Ethanol

Electrically neutral, lipophilic complexing agents were prepared which induce Li+ selectivity in solvent polymeric membranes. Stability constants for group IA and IIA cations of one such ligand in ethanol have been determined. The selectivity behaviour of this ligand in membranes as well as in extraction systems is studied and discussed in terms of model considerations.
A Flexible Stereoselective Synthesis of the Spirosesquiterpenes (±)‐β‐Acorenol, (±)‐β‐Acoradiene, (±)‐Acorenone‐B and (±)‐Acorenone via an Intramolecular Ene‐Reaction
Authors: Oppolzer Wolfgang , Mahalanabis Kumar K. , Bättig Kurt
Published: December 2004

The racemic spirosesquiterpenes β‐acorenol (1), β‐acoradiene (2), acorenone‐B (3) and acorenone (4) (Scheme 2) have been synthesized in a simple, flexible and highly stereoselective manner from the ester 5. The key step (Schemes 3 and 4), an intramolecular thermal ene reaction of the 1,6‐diene 6, proceeded with 100% endo‐selectivity to give the separable and interconvertible epimers 7a and 7b. Transformation of the ‘trans’‐ester 7a to (±)‐1 and (±)‐2 via the enone 9 (Scheme 5) involved either a thermal retro‐ene reaction 10 → 12 or, alternatively, an acid‐catalysed elimination 11 → 13 + 14 followed by conversion to the 2‐propanols 16 and 17 and their reduction with sodium in ammonia into 1 which was then dehydrated to 2. The conversion of the ‘cis’‐ester 7b to either 3 (Scheme 6) or 4 (Scheme 7) was accomplished by transforming firstly the carbethoxy group to an isopropyl group via 7b → 18 → 19 → 20, oxidation of 20 to 21, then alkylative 1,2‐enone transposition 21 → 22 → 23 → 3. By regioselective hydroboration and oxidation, the same precursor 20 gave a single ketone 25 which was subjected to the regioselective sulfenylation‐alkylation‐desulfenylation sequence 25 → 26 → 27 → 4.
Zur Stereochemie der aromatischen Claisen‐Umlagerung. Thermische Umlagerung von erythroiden und threoiden ortho‐Dienonen
Authors: Wunderli Alfred , Winkler Tammo , Hansen Hans‐Jürgen
Published: December 2004

On the Stereochemistry of the Aromatic Claisen Rearrangement. Thermal Rearrangement of erythroid and threoid ortho‐Dienones.

Erythro‐ and threo‐1‐methyl‐1‐(1′‐methyl‐2′‐propynyl)‐2‐oxo‐1,2‐dihydronaph‐thalene (erythro‐ and threo‐6) as well as erythro‐ and threo‐2,6‐dimethyl‐6‐(1′‐methyl‐2′‐propynyl)‐cyclohexa‐2,4‐dien‐1‐one (erythro‐ and threo‐8) were obtained together with the corresponding aromatic ethers 5 and 7 by alkylation of 1‐methyl‐2‐naphthol and 2,6‐dimethyl‐phenol, respectively in alcoholic potassium hydroxide solution with 1‐methyl‐2‐propynyl p‐toluenesulfonate (Scheme 2). The diastereoisomeric dienones 6 and 8 were easily separated by column chromatography on silica gel and its relative configuration at C(1) or C(6) and C(1′) deduced from the chemical shifts in their 1H‐NMR.‐spectra (Table 1). Hydrogenation of 6 and 8 using Lindlar catalyst yielded the corresponding erythro‐ and threo‐configurated (1′‐methyl‐2′‐propenyl)‐dienones 10 and 13, respectively (Scheme 3) the thermal rearrangement of which were studied. The following results were obtained: threo‐10 rearranged in benzene at 85–105° preferentially via a chair‐like (C) transition state to yield 99,5% (E)‐ and 0,5% (Z)‐(2′‐butenyl) 1‐methyl‐2‐naphthyl ether ((E)‐ and (Z)‐14; ΔΔG (C/B) = −4,0 kcal/mol). On the other hand, erythro‐10 when heated at 105‐125° in benzene gave 84,7% (E)‐ and 15,3% (Z)‐14, i.e. in this case a boat‐like (B) transition state is favoured (G (C/B) = + 1,3 kcal/mol) (Scheme 5 and Table 2). The thermal rearrangement of dienones 13 led to the corresponding ethers 12 as well as p‐allyl‐phenols 11. Thus, heating of threo‐13 at 20–42° in cyclohexane resulted in the formation of 2,5% of ether 12, consisting of 98% of the (E)‐ and 2% of the (Z)‐isomer, and 97,5% of (E)‐11 which contained, at a maximum, 0,5% of the (Z)‐isomer, (Scheme 6 and Table 3). This means that both rearrangements occurred with a strong preference of the C transition state (G (C/B, phenol) = −3,3 kcal/mol). On the contrary, erythro‐13 when heated at 42–68° in cyclohexane yielded a 3:2 mixture of ether 12 and phenol 11 (Scheme 6). The ethereal part consisted of 88,0% of the (E)‐ and 12,0% of the (Z)‐isomer which again shows that the B geometry predominated in the erythro transition state leading to the ether (G (C/B)= + 1,3 kcal/mol). In the phenolic part 36–40% of the (E)‐isomer and 64–60% of (Z)‐isomer were found which means that in the para‐Claisen rearrangement of erythro‐13 the C arrangement is only slightly favoured (ΔΔG (C/B)= −0,36 kcal/mol).
Synthese und IR.‐spektroskopische Identifizierung epimerer 3‐Äthinyl‐5 α‐cholestan‐3‐ole
Authors: Berbalk Hans , Eichinger Karl , Schuster Rudolf
Published: December 2004

Synthesis and IR. Spectroscopic Identification of Epimeric 3‐Ethinyl‐5α‐cholestan‐3‐ols

The syntheses of the 3β‐ethinyl‐5α‐cholestan‐3α‐ols 2a, 2b, 2c and of the corresponding epimeric 3α‐ethinyl‐5 α‐cholestan‐3 β‐ols 3a, 3b, 3c are described. Bands at 1000 cm−1 for the α‐alcohols and at 1030 cm−1 for the β‐alcohols are found to be useful for the IR. spectroscopic identification of epimeric 3‐ethinyl‐5α‐cholestan‐3‐ols.