Triphenanthro‐anellierte [18]Annulene mit Alkoxy‐Seitenketten — Eine neue Klasse discotischer Flüssigkristalle

Triphenanthro-Anellated [18]Annulenes with Alkoxy Side Chains - A Novel Class of Discotic Liquid Crystals Two different types 6 and 16 of [18]annulenes condensed with phenanthrene systems were prepared by cyclocondensation reactions (Schemes 2 and 3). The central 18-membered rings do not show a macrocyclic diamagnetic ring current. Conformational analyses and X-ray analyses in the solid state reveal non-planar structures in which aromatic “islands” are connected by (E)-configurated olefinic bridges. The introduction of long alkoxy side chains yields a new class of discotic liquid crystals; either ND or hexagonal columnar phases are generated, which were characterized by DSC, microscopy with…

Isolation, structure elucidation, and biological evaluation of the unusual heterodimer chrysoxanthone from the ascomycete IBWF11-95A

Chrysoxanthone, an unusual heterodimer of blennolide A and 2-hydroxychrysophanol linked through a diaryl ether bridge, was isolated from mycelia of the ascomycete IBWF11-95A grown in submerged culture. Its structure was elucidated by two-dimensional NMR spectroscopy. The metabolite shows antibacterial activity against different species with MIC values between 2.5 and 20 μg/mL while also inhibiting the growth of several fungi.

Omphalotins E-I, Five Oxidatively Modified Nematicidal Cyclopeptides fromOmphalotus olearius

Omphalotins E–I, oxidatively modified cyclic dodecapeptides, were isolated from mycelial extracts of the basidiomycete Omphalotus olearius, and their structures were determined by NMR spectroscopic and MS methods. Four of the five omphalotins contained an unprecedented N-hydroxylated tricyclic tryptophan derivative. All compounds exhibited strong and selective nematicidal activity against the plant pathogen Meloidogyne incognita with LD90 values between 2 and 5 μg mL–1. Cytotoxic activities were not detected up to 50 μg mL–1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Oligo(phenylenevinylene)s with Terminal Donor–Acceptor Substitution This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.

Cyclooctadienine — hoch gespannte C 8 H 8 ‐Kohlenwasserstoffe

Mit Hilfe der MNDO-Methode werden die energiearmsten Konformationen der vier strukturisomeren Cyclooctadienine 1–4 berechnet. Aus ihren Bildungswarmen ΔHf konnen durch Bezug zu den Cyclooctatrienen 5 und 6 die geometrischen Ringspannungen Eg abgeschatzt werden. Als experimentelle Sonde fur die Ringspannung dienen die UV-, IR (Raman)- und 13C-NMR-Spektren. Cyclooctadienynes — Highly Strained C8H8-Hydrocarbons Applying the MNDO-method the conformations with lowest energy of the isomeric cyclooctadienynes 1–4 are calculated. The geometrical ring strains Eg can be evaluated from the enthalpies of formation ΔHf in relation to the cyclooctatrienes 5 and 6. UV, IR (Raman) and 13C NMR spectra serve…

ChemInform Abstract: Sterelactones: New Isolactarane Type Sesquiterpenoids with Antifungal Activity from Stereum sp. IBWF 01060.

Four members of a new family of tetracyclic sesquiterenoids possessing the isolactarane skeleton have been isolated from mycelial cultures of Stereum sp. IBWF 01060. Their structure elucidation and their antifungal activity against several plant pathogens as well as other microorganisms are reported.

Step growth polymerization via tandem ene and diels-alder reactions

In contrast to other electron deficient enophiles or dienophiles which react with 1,4-cyclohexadiene (1,4-CHD) under aromatization, 1,2,4-triazoline-3,5-diones react in a defined reaction sequence. In a first step the 1,4-cyclohexadiene reacts via an ene-reaction. The intermediately formed substituted 1,3-cyclohexadiene immediately reacts in a Diels-Alder reaction. The regiochemistry of the Diels-Alder reaction is controlled by the solvent polarity. This reaction sequence can be used to synthesize polymers. Low-molar-mass model compounds were synthesized to elucidate the stereochemistry of the polymers. By varying the bistriazolinedione, polymers with backbones of different rigidity are ava…

Preparation of 2-amino-5-methyl-7H-1,3,4-thiadiazolo[3,2-α]pyrimidin-7-ones

2-Amino substituted 7H-1,3,4-thiadiazolo[3,2-α]pyrimidin-7-ones 11a-e were prepared by the reaction of 2-bromo-5-amino-1,3,4-thiadiazole (1b) and diketene (8), subsequent cyclocondensation (9b 3b) and displacement of the bromo substituents by the reaction with primary or secondary amines (3b 11a-e). The hydrogen atom 6-H in the heterobicycle 3b is replaced by a Cl or Br atom in the transformation of 3b 14a,b. The 2-bromo-6-chloro compound 14a reacts chemoselectively in the 2-position with dimethylamine (14a 15). The structure elucidations are based on one- and two-dimensional NMR techniques including a heteronuclear NOE measurement.

Introduction of unsaturated segments in the bridge of metacyclophanes

Abstract The cyclophanes 2a,b, which contain a triple bond in the meta-bridge, were transformed to the allenes 3a,b by the action of bases or acids. A further isomerization yielded the dienes 4a,b with ( E,Z )- or ( Z,Z )-configuration.

Isomerisierung der Dihydropentalene und Umsetzung mit Tetracyanethylen

Zwischen den sechs isomeren Dihydropentalenen 1–6 existieren eine Reihe von H-Verschiebungen (Schema 1), die in Gasphasenpyrolysen untersucht werden. Der thermodynamisch kontrollierte irreversible Ausgang aus den Gleichgewichten von 1–6 fuhrt uber 1-Vinylfulven (14) zu Styrol (15). Praparativ nutzlich ist besonders die katalytische Isomerisierung zwischen 1,5-DHP (4) und 1,2-DHP (1) bei Raumtemperatur. Die Umsetzung der Dihydropentalene mit Tetracyanethylen liefert bei 1 das [2+2]-Addukt 24, bei 3 und 5 die [4+2]-Addukte 25 bzw. 26 und bei 4 das doppelte [4+2]-Addukt 22.2 und 6 lassen sich unter Blitzpyrolyse-Bedingungen mit TCNE nicht abfangen. Isomerization of Dihydropentalenes and Reacti…

Ring-expansion of 5-methylene-thiazolidine-2-thione with hydrazine

ChemInform Abstract: 1-Alkyl- and Azeto[1,2-a][1,5]benzodiazepine Derivatives in the Reaction of o-Phenylenediamine with 3-(Dimethylamino)propiophenones.

The reaction of o-phenylenediamine (4) with one, two or three equivalents of p-substituted 3-dimethylaminopropiophenone hydrochlorides 5a−e was studied. 4-Aryl-2,3-dihydro-1H-1,5-benzodiazepine derivatives 6a−e were obtained in good yields, along with the 1:2-adducts 7c−e and the unexpected 1:3-adducts rac-8c−e. The type of adduct formed is determined by the molar ratio of the reactants 4 and 5 and by the nature of the substituent in the para position of the propiophenone 5.

Synthese von 9‐Oxabicyclo[6.1.0]non‐3‐in

Ausgehend von 1,5-Cyclooctadien (1) wird in einer siebenstufigen Synthese die Titelverbindung 9 gewonnen. Sie liegt in zwei Konformationen 9a und 9b vor, wobei in 9a eine starke sterische Wechselwirkung zwischen dem Sauerstoffatom und der gespannten Dreifachbindung auftritt. Zur Einfuhrung der Dreifachbindung dient die thermische Fragmentierung des 1,2,3-Selenadiazols 7. Der Strukturnachweis fur die regiospezifische Bildung von 7 wird mit 2D-NMR-Spektroskopie gefuhrt. Starting with 1,5-cyclooctadiene (1), the title compound 9 is gained in a synthesis of seven steps. 9 exists in two conformations 9a and 9b, of which 9a shows a strong interaction between the oxygen atom and the strained tripl…

Extension of Conjugation Leading to Bathochromic or Hypsochromic Effects in OPV Series

Four OPV series 1-4 (a-d) with a terminal dialkylamino group as electron donor were prepared by Wittig-Horner reactions. To study the influence of the push-pull effect on the long-wavelength absorption, three of the four series contained terminal acceptor groups (CN, CHO, NO(2)). The length of the chromophores strongly affects the intramolecular charge transfer (ICT)-an effect which superimposes upon the extension of the conjugation. Increasing numbers n of repeat units cause an overall bathochromic shift for the purely donor-substituted series 1 a-4 a and the series 1 b-4 b with CN as weak acceptor. The two effects annihilate each other in the series 1 c-4 c with terminal CHO groups, so th…

Red- and Blue-Shifts in Oligo(1,4-phenyleneethynylene)s Having Terminal Donor−Acceptor Substitutions

Four series of oligo(1,4-phenyleneethynylene)s (OPEs), 1−4 (a−d), each having a terminal dialkylamino group as their electron donor, were prepared by applying Sonogashira−Hagihara reactions and a protecting group strategy. To study the influence that the push−pull effect has on the long-wavelength absorption, three of the four series of OPEs contain terminal acceptor groups (CN, CHO, NO2). Extending the conjugation (increasing the number of repeat units, n) lowers the energy E(n) of the electron transition in the purely donor-substituted series 1a−4a (bathochromic shift). This effect is superimposed in the push−pull series 1−4 (b−d) by the effect of the intramolecular charge transfer (ICT),…

Dithiametacyclophane mit Dreifachbindungen

Dithiametacyclophanes with Triple Bonds Schemes 1 and 2 show the syntheses of dithia[8]metacyclo-phanes 4a-d and tetrathia[m.n]metacyclophanes 9, 10 by cyclization reactions applying the cesium effect. All these cyclophanes contain C—C triple bonds which influence the molecular dynamics; especially the halogen substituents in 4b-d obstruct the topomerization.

1-Alkyl- and azeto[1,2-a][1,5]benzodiazepine derivatives in the reaction of o-phenylenediamine with 3-(dimethylamino)propiophenones

The reaction of o-phenylenediamine (4) with one, two or three equivalents of p-substituted 3-dimethylaminopropiophenone hydrochlorides 5a−e was studied. 4-Aryl-2,3-dihydro-1H-1,5-benzodiazepine derivatives 6a−e were obtained in good yields, along with the 1:2-adducts 7c−e and the unexpected 1:3-adducts rac-8c−e. The type of adduct formed is determined by the molar ratio of the reactants 4 and 5 and by the nature of the substituent in the para position of the propiophenone 5.

Hirsutane-Type Sesquiterpenes with Uncommon Modifications from Three Basidiomycetes

From three basidiomycetes, Xeromphalina sp., Stereum sp., and Pleurocybella porrigens, six triquinane sesquiterpenes with unprecendented modifications and a rearranged sesquiterpene related to coriolin C have been isolated. Their isolation, structure elucidation, and biological evaluation are described.

ChemInform Abstract: Phenylethynyl- and Phenylethenylmetacyclophanes.

The cyclophanes 6,8,10 and 13–15 were synthesized by cesium assisted ring closure reactions. The main interest in these systems concerns the interaction of the unsaturated bridge with the tolan and the stilbene chromophores, respectively.

Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls

Summary Methyl methacrylate was polymerized with tert-butyl lithium in the presence of triethylaluminum or triisobutylaluminium at -78~ in toluene. As indicated by GPC and MALDI-TOF mass spectrometry, the polymerization is accompanied by side reactions. The lower oligomers were fractionated by distillation and characterised by NMR, FT-IR, UV and electron impact (EI) mass spectrometry. All these data show that part of the polymer chains are carrying exactly one tert-butyl isoprenyl ketone unit. In order to avoid the formation of tert-butyl isoprenyl ketone a molar ratio of A1/Li > 2 is necessary.

ChemInform Abstract: A Versatile Synthesis of 4,5-Dihydropyrrolo[1,2-a]quinoxalines.

The reaction of 1-(2-aminophenyl)pyrrole with aromatic or heteroaromatic aldehydes in ethanol and catalytic amounts of acetic acid leads to 4,5-dihydropyrrolo[1,2-a]quinoxalines in high yields. When aliphatic aldehydes were used under the same conditions, a slow oxidation to the corresponding pyrrolo[1,2-a]quinoxalines can occur; the oxidation can be avoided by preparing in situ the 5-acetyl derivatives of the 4,5-dihydropyrrolo[1,2-a]quinoxalines.

Generation and transformation of the [3.3.1]propellane skeleton by thermal rearrangements

Abstract In a sequence of unexpected thermal rearrangements the strained monocyclic alkyne 4 is transformed into the tricyclic system 5 which yields in a flash vacuum pyrolysis again a monocyclic compound 10 .

ChemInform Abstract: Ring-Expansion of 5-Methylene-thiazolidine-2-thione with Hydrazine.

ChemInform Abstract: Omphalotins E-I, Five Oxidatively Modified Nematicidal Cyclopeptides from Omphalotus olearius.

Omphalotins E–I, oxidatively modified cyclic dodecapeptides, were isolated from mycelial extracts of the basidiomycete Omphalotus olearius, and their structures were determined by NMR spectroscopic and MS methods. Four of the five omphalotins contained an unprecedented N-hydroxylated tricyclic tryptophan derivative. All compounds exhibited strong and selective nematicidal activity against the plant pathogen Meloidogyne incognita with LD90 values between 2 and 5 μg mL–1. Cytotoxic activities were not detected up to 50 μg mL–1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

On the basis of an extended series of monodisperse oligomers of the dialkoxy-substituted phenyleneethenylenes 1a–i the Eqs. (3) and (4) were conceived in order to determine the limiting values of the energies Ei and the wavelengths λi of the UV/vis absorption. The convergence of the Ei, and λi values with a growing number n of repeating units permits a precise prediction of the Ei,∞ and λi,∞ values of the corresponding polymer 1j as well as a statement about the overall effect of conjugation ΔEi and the effective conjugation length ECL. A great variety of different conjugated oligomers 2–14 can be evaluated by the same algorithm.

Oligo(phenylenvinylene) mit terminaler Donor-Acceptor-Substitution

New Alkaloids of the Sarpagine Group from Rauvolfia serpentina Hairy Root Culture

Three new monoterpenoid indole alkaloids, 19(S),20(R)-dihydroperaksine (1), 19(S),20(R)-dihydroperaksine-17-al (2), and 10-hydroxy-19(S),20(R)-dihydroperaksine (3), along with 16 known alkaloids 4-19 were isolated from hairy root culture of Rauvolfia serpentina, and their structures were elucidated by 1D and 2D NMR analyses. Taking into account the stereochemistry of the new alkaloids and results of preliminary enzymatical studies, the putative biosynthetical relationships between the novel alkaloids are discussed.

Monodisperse Dialkoxy-Substituted Oligo(phenyleneethenylene)s

Individual but connected synthetic routes for the preparation of the all-E-configured 2,5-dipropoxy-substituted oligo(1,4-phenyleneethenylene)s 1a–g were developed. An increasing number of conjugated stilbene units from n = 1 to n = 11 led to a convergent bathochromic shift (Δλ = λ∞ − λ1 = 127 nm) in the UV/Vis absorption. An exponential function for the convergence of the absorption energies (wavelengths) in conjugated systems is proposed. By a simple extrapolation of this function the effective chain length may be determined.

Isolation and Structure Elucidation of a New Indole Alkaloid from Rauvolfia serpentina Hairy Root Culture: The First Naturally Occurring Alkaloid of the Raumacline Group

A new monoterpenoid indole alkaloid, 10-hydroxy- N(alpha)-demethyl-19,20-dehydroraumacline ( 1), was isolated as a mixture of E- and Z-isomers from hairy root culture of Rauvolfia serpentina Benth. ex Kurz (Apocynaceae) and the structure was determined by 1D and 2D NMR analyses. The new indole alkaloid represents the first naturally occurring alkaloid of the raumacline group and its putative biosynthetical pathway is discussed.

Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls, 1. 13C NMR studies of model compounds in toluene

The bimetallic ate complex [(CH 3 ) 2 C=C(OEt)(O - AlR 3 )]Li + is regarded to be the model of the active centre of the polymerization of methyl methacrylate in the presence of aluminium alkyls. This complex is detectable by 13 C NMR up to 273 K. At ambient temperature irreversible decomposition takes place. Apart from the formation of the ate complex, excess aluminium chloride coordinates to the ester carbonyl groups of both the monomer and the polymer chain

Polymerization of Triazolinediones withtrans-3,3-Dichloro-1-phenyl-1-propene

The reaction of 4-phenyl-1,2,4-triazoline-3,5-dione (PhTD) (2) with trans-3,3-dichloro-1-phenyl-1-propene (4) was investigated at room and reflux temperatures in methylene chloride solution. Although the reaction is slow, it gives quantitative yield. This reaction leads to the formation of two 2:1 adducts via double Diels–Alder and Diels–Alder-Ene reactions in a ratio of about 1: 7. The major product was isolated by means of fractional crystallization as a pure compound and was characterized by infra-red (IR), 1H nuclear magnetic resonance (NMR), 13C NMR, mass spectra and elemental analysis. The structure of the minor product was determined by IR and 1H NMR. These compounds were used as mod…

Untersuchungen zur Konformerenvielfalt von mono- und 2,5-dialkoxysubstituierten Poly(1,4-phenylenethenylen)en

Investigations on the Conformational Variety of Mono- and 2,5-Dialkoxy Substituted Poly(1,4-phenyleneethenylene)s The alkoxy substituted poly(1,4-phenyleneethenylene)s 1 and 2 can principally exist in an enormous variety of conformers (table 1). However, force field calculations (MMX) reveal a far-reaching restriction to a relatively small number of non planar conformers with minimized steric energy. The decisive criterion is due to the interaction between the oxygen atoms and the olefinic hydrogens. An increasing steric hindrance should lead to higher twist angles θ in the main chain and hence to a shorter effective conjugation length. Such an effect could play a minor role between the uns…

Sterelactones: New Isolactarane Type Sesquiterpenoids with Antifungal Activity from Stereum sp. IBWF 01060

Four members of a new family of tetracyclic sesquiterenoids possessing the isolactarane skeleton have been isolated from mycelial cultures of Stereum sp. IBWF 01060. Their structure elucidation and their antifungal activity against several plant pathogens as well as other microorganisms are reported.

Oxacyclododecindione, a Novel Inhibitor of IL-4 Signaling from Exserohilum rostratum

In a screening program for new metabolites from fungi inhibiting the IL-4 mediated signal transduction, a novel chlorinated macrocyclic lactone, designated as oxacyclododecindione, was isolated from fermentations of the imperfect fungus Exserohilum rostratum. The structure was determined by a combination of spectroscopic techniques. Oxacyclododecindione inhibits the IL-4 induced expression of the reporter gene secreted alkaline phosphatase (SEAP) in transiently transfected HepG2 cells with IC50 values of 20-25 ng/ml (54-67.5 nM). Studies on the mode of action of the compound revealed that the inhibition of the IL-4 dependent signaling pathway is caused by blocking the binding of the activat…

On the anionic polymerization of dialkylaminoisoprenes, 3. A nuclear magnetic resonance study of the structure of oligo[5-(N,N-diisopropylamino)isoprenyllithium]

The structure of oligo[(5-N,N-diisopropylamino)isoprenyllithium] (number-average degree of polymerization Pn = 1-2) prepared by reaction of alkyllithium with 5-(N,N-diisopropylamino)-isoprene1 in nonpolar (benzene) and polar (tetrahydrofuran) solvents has been studied by 1H and 13C NMR spectroscopy. In tetrahydrofuran, as expected, the negative charge at the terminal chain unit is more delocalized than in benzene and, consequently, the carbon-lithium bond has a more ionic character. In both solvents the living chain end shows a cisoid-4, 1-structure. No cistrans isomerization could be detected. This independence of the carbanion structure of the solvent polarity is explained by the complexa…

Konvergenz von Absorption und Fluoreszenz bei gekreuzt konjugierten Oligomeren aus Chalkon-Bausteinen

The absorption and fluorescence spectra of two series of chalcone oligomers (1a–d) and (2a–d) are reported. Due to small or vanishing orbital coefficients (HMO calculation) within the cross-conjugated systems, the bathochromic shifts caused by the extension of the chains are modest. The effective conjugation lengths amount to 6 and 14 chalcone building blocks in the absorptions of the series 1 and 2. The convergence of the fluorescence bands is already reached in 1d and 2d with 4 and 8 enone units, respectively. Besides the uniform or alternate arrangement of the chalcone building blocks, the positions of the propoxy substituents show a considerable influence on the electronic transitions p…

A versatile synthesis of 4,5-dihydropyrrolo[1,2-a]quinoxalines

The reaction of 1-(2-aminophenyl)pyrrole with aromatic or heteroaromatic aldehydes in ethanol and catalytic amounts of acetic acid leads to 4,5-dihydropyrrolo[1,2-a]quinoxalines in high yields. When aliphatic aldehydes were used under the same conditions, a slow oxidation to the corresponding pyrrolo[1,2-a]quinoxalines can occur; the oxidation can be avoided by preparing in situ the 5-acetyl derivatives of the 4,5-dihydropyrrolo[1,2-a]quinoxalines.

The Creolophins: A Family of Linear Triquinanes fromCreolophus cirrhatus (Basidiomycete)

Complicatic acid and five novel linear triquinanes were isolated from mycelial cultures of Creolophus cirrhatus. The creolophins A, C, D, and E represent a novel type of highly oxidized triquinane sesquiterpenoids. Whereas those compounds with a secondary alcohol moiety in ring A are stable, the exomethylene ketone creolophin E (5) partly dimerized during workup to form the decacyclic 1,4-dioxepin-6-one neocreolophin (6). Compounds 5 and 6 display cytotoxic activities against several tumor cell lines.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)