Thomas Rosenau

Publications

• 5.50

  Impact points

  Chiroptical properties of an alternatingly functionalized cellotriose bearing two porphyrin groups.

  Keita Sakakibara, Fumiaki Nakatsubo, Alfred D French, Thomas Rosenau

  Chemical communications (Cambridge, England). 04/2012;

  Right-handedness derived from bisporphyrins attached to a cellotriose backbone at O-6 and O''-6 positions is revealed for the first time. This cellotriose is proposed as a model of alternatingly functionalized cellulosics, which have promising properties for applications in optoelectronics a... [more] Right-handedness derived from bisporphyrins attached to a cellotriose backbone at O-6 and O''-6 positions is revealed for the first time. This cellotriose is proposed as a model of alternatingly functionalized cellulosics, which have promising properties for applications in optoelectronics and molecular receptors owing to the chirality and rigid backbone effects.
• 4.19

  Impact points

  Determination of carbohydrate- and lignin-derived components in complex effluents from cellulose processing by capillary electrophoresis with electrospray ionization-mass spectrometric detection.

  Anna Bogolitsyna, Manuel Becker, Anne-Laurence Dupont, Andrea Borgards, Thomas Rosenau, Antje Potthast

  Journal of chromatography. A. 11/2011; 1218(47):8561-6.

  Degradation products from lignocellulosic materials receive increasing attention due to the continuously growing interest in their utilization. The inherent structural variance of lignocellulosics combined with the intricacy of lignocellulosic processing (e.g. pulping of wood and bleaching of cellul... [more] Degradation products from lignocellulosic materials receive increasing attention due to the continuously growing interest in their utilization. The inherent structural variance of lignocellulosics combined with the intricacy of lignocellulosic processing (e.g. pulping of wood and bleaching of cellulosic pulps) and the complexity of degradation processes occurring therein result in rather complex mixtures in the process streams and effluents that contain a large quantity of structurally different degradation products. This is true for most processing steps, but also for degradation reactions occurring during aging of lignocellulosic materials, such as paper, cellulosic tissue or textiles. In order to render such mixtures better analytically accessible than hitherto possible a CE-ESI-MS method was established for the simultaneous determination of aliphatic carboxylic acids from the degradation of (hemi)celluloses and aromatic compounds from lignin degradation. CE and ESI-MS parameters have been optimized towards sensitivity and good reproducibility. The method was tested in two real-world scenarios: the determination of major components in effluents from bleaching stages in the pulp and paper industry, and the analysis of degradation products in extracts of naturally aged papers. The advantages and drawbacks of this approach are critically discussed.
• 2.82

  Impact points

  Synthesis and characterization of 5-alkoxycarbonyl-4-hydroxymethyl-5-alkyl-pyrroline N-oxide derivatives.

  Anjan Patel, Natascha Rohr-Udilova, Thomas Rosenau, Klaus Stolze

  Bioorganic & medicinal chemistry. 10/2011; 19(24):7643-52.

  The syntheses, analytical properties, and spin trapping behavior of four novel EMPO derivatives, namely 5-ethoxycarbonyl-4-hydroxymethyl-5-methyl-pyrroline N-oxide (EHMPO), 5-ethoxycarbonyl-5-ethyl-4-hydroxymethyl-pyrroline N-oxide (EEHPO), 4-hydroxymethyl-5-methyl-5-propoxycarbonyl-pyrroline N-oxid... [more] The syntheses, analytical properties, and spin trapping behavior of four novel EMPO derivatives, namely 5-ethoxycarbonyl-4-hydroxymethyl-5-methyl-pyrroline N-oxide (EHMPO), 5-ethoxycarbonyl-5-ethyl-4-hydroxymethyl-pyrroline N-oxide (EEHPO), 4-hydroxymethyl-5-methyl-5-propoxycarbonyl-pyrroline N-oxide (HMPPO), and 4-hydroxymethyl-5-methyl-5-iso-propoxycarbonyl-pyrroline N-oxide (HMiPPO), towards different oxygen- and carbon-centered radicals are described.
• 11.83

  Impact points

  Ammonoxidised lignins as slow nitrogen-releasing soil amendments and CO₂-binding matrix.

  Falk Liebner, Georg Pour, José Maria de la Rosa Arranz, André Hilscher, Thomas Rosenau, Heike Knicker

  Angewandte Chemie (International ed. in English). 09/2011; 50(37):A34-9.

  Nitrogen (N) is a major nutrient element controlling the cycling of organic matter in the biosphere. Its availability in soils is closely related to biological productivity. In order to reduce the negative environmental impact, associated with the application of mineral N-fertilizers, the use of amm... [more] Nitrogen (N) is a major nutrient element controlling the cycling of organic matter in the biosphere. Its availability in soils is closely related to biological productivity. In order to reduce the negative environmental impact, associated with the application of mineral N-fertilizers, the use of ammonoxidised technical lignins is suggested. They can act as potential slow N-release fertilisers which concomitantly may increase C sequestration of soils by its potential to bind CO₂. The idea of our study was to combine an improved chemical characterisation of ammonoxidised ligneous matter as well as their CO₂-binding potential, with laboratory pot experiments, performed to enable an evaluation of their behaviour and stability during the biochemical reworking occurring in active soils.
• 2.82

  Impact points

  Tocotrienamines and tocopheramines: reactions with radicals and metal ions.

  Francesco Galli, Francesco Mazzini, Luca Bamonti, Lars Gille, Stefan Böhmdorfer, Marta Piroddi, Thomas Netscher, Frank J Kelly, Thomas Rosenau

  Bioorganic & medicinal chemistry. 08/2011; 19(21):6483-91.

  The antioxidant activity of vitamin E (VE) homologs α, γ and δ-tocotrienamines (4b-6b), never studied before, and α, γ and δ-tocopheramines (4a-7a) was investigated by means of different total antioxidant capacity (TAC) tests. In all the test model systems, compounds 4a-7a and 4b-6b showed similar o... [more] The antioxidant activity of vitamin E (VE) homologs α, γ and δ-tocotrienamines (4b-6b), never studied before, and α, γ and δ-tocopheramines (4a-7a) was investigated by means of different total antioxidant capacity (TAC) tests. In all the test model systems, compounds 4a-7a and 4b-6b showed similar or higher TAC values than the parental vitamin E forms and their physiological metabolites. α-Homologs of VE amines showed markedly higher activity than the VE congeners in the TEAC test, which is tailored for liposoluble antioxidants, while γ-homologs of the amine analogs showed higher activity in the FRAP tests. Kinetics analysis of the reaction with DPPH(·) showed higher second order rate k for 4a than for α-tocopherol (1a). α-Tocopherolquinone 1f was the common main oxidation product for both 1a and α-tocopheramine (4a) exposed to ferric ions or DPPH(·), and the implied oxidative deamination of 4a was accompanied by a nitration reaction of phenolic substrates that were added to the reaction medium. Possible mechanisms of these reactions were studied.
• 3.22

  Impact points

  Novel tocopherol derivatives. Part 32: On the bromination of pyrano[3,2-f]chromenes related to γ-tocopherol.

  Stefan Böhmdorfer, Elisabeth Kloser, Anjan Patel, Lars Gille, Kurt Mereiter, Thomas Rosenau

  Tetrahedron. 08/2011; 67(34):6181-6185.

  While bromination of γ-tocopherol (2) with elemental bromine affords 5-bromo-γ-tocopherol quantitatively (3), the analogous reaction of its truncated model compound, 2,2,7,8-tetramethylchromanol (2a) is known to be accompanied by side reactions and to produce hitherto unknown byproducts. These compo... [more] While bromination of γ-tocopherol (2) with elemental bromine affords 5-bromo-γ-tocopherol quantitatively (3), the analogous reaction of its truncated model compound, 2,2,7,8-tetramethylchromanol (2a) is known to be accompanied by side reactions and to produce hitherto unknown byproducts. These compounds originate from pyrano[3,2-f]chromene (6), a byproduct in the synthesis of model compound 2a, which affords bromochromene 7 as the major product. The reaction mechanism was shown to proceed via chromene 8 and its 1,2-dibromo addition compound 9, which eliminates HBr in an E1 process to finally afford 7. Analytical data including crystal structures of both 6 and 7 are reported.
• 4.50

  Impact points

  Dissolution behavior of different celluloses.

  Ute Henniges, Mirjana Kostic, Andrea Borgards, Thomas Rosenau, Antje Potthast

  Biomacromolecules. 03/2011; 12(4):871-9.

  Celluloses from different origins were dissolved stepwise in N,N-dimethylacetamide/lithium chloride (9% v/w; DMAc/LiCl) with the aim to study the time course of the dissolution process, completeness of dissolution in the dissolved fractions, possible discrimination effects, and differences between t... [more] Celluloses from different origins were dissolved stepwise in N,N-dimethylacetamide/lithium chloride (9% v/w; DMAc/LiCl) with the aim to study the time course of the dissolution process, completeness of dissolution in the dissolved fractions, possible discrimination effects, and differences between the celluloses. Cellulosic pulps from both annual plants and different wood species were analyzed. The obtained fractions were subject to gel permeation chromatography (GPC) with multiple detection to monitor the development of molecular mass distribution (MMD), molecular mass, and recovered mass. The dissolution behavior of accompanying xylans was followed by quantitative analysis of the uronic acids by fluorescence labeling--GPC. The morphological changes at the remaining fibers in the stepwise dissolution were addressed by SEM. The time needed to dissolve completely the cellulosic pulp differed from species to species, mainly between pulps from annual plants and pulps from wood. Annual plants generally needed much longer to dissolve completely. In the beginning of the dissolution, the dissolved fractions of annual plants showed a distinct discrimination effect because they were enriched in hemicellulose. By contrast, wood pulps dissolve fast and without distinct changes in the MMD of the dissolved fractions over time. Bagasse pulp is an exception to the observation for annual plants and rather resembled the behavior of wood celluloses. Prolonged dissolution times, as often practiced in cellulose GPC, do not lead to any improvements regarding the determination of molecular mass, MMD, and recovered mass of injected sample, so that the dissolution times required for reliable GPC analysis can be significantly shortened, which will be important for biorefinery analytics with high numbers of samples.
• 2.82

  Impact points

  Synthesis and characterization of 5-hydroxymethyl-5-methyl-pyrroline N-oxide and its derivatives.

  Klaus Stolze, Natascha Rohr-Udilova, Anjan Patel, Thomas Rosenau

  Bioorganic & medicinal chemistry. 01/2011; 19(2):985-93.

  Synthesis and spin trapping behavior of three novel DMPO derivatives, namely 5-hydroxymethyl-5-methyl-pyrroline N-oxide (HMMPO), 5-(2-furanyl)-oxymethyl-5-methyl-pyrroline N-oxide (FMMPO), and 5-(2-pyranyl)-oxymethyl-5-methyl-pyrroline N-oxide (PMMPO) towards different oxygen- and carbon-centered ra... [more] Synthesis and spin trapping behavior of three novel DMPO derivatives, namely 5-hydroxymethyl-5-methyl-pyrroline N-oxide (HMMPO), 5-(2-furanyl)-oxymethyl-5-methyl-pyrroline N-oxide (FMMPO), and 5-(2-pyranyl)-oxymethyl-5-methyl-pyrroline N-oxide (PMMPO) towards different oxygen- and carbon-centered radicals are described. The stabilizing effect of a series of cyclodextrins on the superoxide adducts was tested.
• 3.11

  Impact points

  Aerogels from unaltered bacterial cellulose: application of scCO2 drying for the preparation of shaped, ultra-lightweight cellulosic aerogels.

  Falk Liebner, Emmerich Haimer, Martin Wendland, Marie-Alexandra Neouze, Kerstin Schlufter, Peter Miethe, Thomas Heinze, Antje Potthast, Thomas Rosenau

  Macromolecular bioscience. 02/2010; 10(4):349-52.

  Bacterial cellulose produced by the gram-negative bacterium Gluconacetobacter xylinum was found to be an excellent native starting material for preparing shaped ultra-lightweight cellulose aerogels. The procedure comprises thorough washing and sterilization of the aquogel, quantitative solvent excha... [more] Bacterial cellulose produced by the gram-negative bacterium Gluconacetobacter xylinum was found to be an excellent native starting material for preparing shaped ultra-lightweight cellulose aerogels. The procedure comprises thorough washing and sterilization of the aquogel, quantitative solvent exchange and subsequent drying with supercritical carbon dioxide at 40 degrees C and 100 bar. The average density of the obtained dry cellulose aerogels is only about 8 mg x cm(-3) which is comparable to the most lightweight silica aerogels and distinctly lower than all values for cellulosic aerogels obtained from plant cellulose so far. SEM, ESEM and nitrogen adsorption experiments at 77 K reveal an open-porous network structure that consists of a comparatively high percentage of large mesopores and smaller macropores.
• 4.36

  Impact points

  Tocopheryl quinones and mitochondria.

  Lars Gille, Katrin Staniek, Thomas Rosenau, J Catharina Duvigneau, Andrey V Kozlov

  Molecular nutrition & food research. 02/2010; 54(5):601-15.

  In the past, the role of tocopherols and tocopheryl hydroquinones as antioxidants in mitochondria has been examined. However, structural properties of tocopherols and tocopheryl quinones (arrangement of polar/apolar moieties) have also been recognized as being crucial for the selective transport of ... [more] In the past, the role of tocopherols and tocopheryl hydroquinones as antioxidants in mitochondria has been examined. However, structural properties of tocopherols and tocopheryl quinones (arrangement of polar/apolar moieties) have also been recognized as being crucial for the selective transport of RRR-alpha-congeners compared with other tocopherols in the cell, suggesting that these properties might be generally important for the binding of vitamin E-related compounds to proteins and enzymes in mitochondria. Therefore, direct modulation of mitochondrial activities, such as bioenergetics, production of reactive oxygen species and apoptosis, not exclusively related to the redox activity of these compounds is increasingly studied. This overview focuses on the influence of alpha-/gamma-tocopheryl quinones and their parent alpha-/gamma-tocopherols on mitochondrial functions, including formation of tocopheryl quinones, their analytical aspects, their potential as alternative substrates and their inhibitory activity for some mitochondrial functions. It is shown that the understanding of how tocopheryl quinones and tocopherols interfere with mitochondrial functions on the molecular level is still incomplete and that a better comprehension requires further research activities.
• 3.74

  Impact points

  Modulation of the Mitochondrial Cytochrome bc(1) Complex Activity by Chromanols and Related Compounds.

  Andrea Müllebner, Anjan Patel, Werner Stamberg, Katrin Staniek, Thomas Rosenau, Thomas Netscher, Lars Gille

  Chemical research in toxicology. 12/2009;

  Tocopherols (alpha-, beta-, gamma-, and delta-Toc) and tocopheryl quinones (alpha-, beta-, gamma-, and delta-TQ) were recently suggested to modulate mitochondrial electron transfer in mammals. Intriguingly, Tocs and stigmatellin, a potent inhibitor of the mitochondrial cytochrome (cyt) bc(1) complex... [more] Tocopherols (alpha-, beta-, gamma-, and delta-Toc) and tocopheryl quinones (alpha-, beta-, gamma-, and delta-TQ) were recently suggested to modulate mitochondrial electron transfer in mammals. Intriguingly, Tocs and stigmatellin, a potent inhibitor of the mitochondrial cytochrome (cyt) bc(1) complex, possess a common structural feature: the chroman core. Therefore, we studied the interference of Tocs as well as synthetic model compounds (low molecular weight TQ analogues and tetramethyl chromanones) at the mitochondrial cyt bc(1) complex. Enzymatic experiments revealed that besides the inhibitor stigmatellin, among natural vitamin E-related derivatives, gamma-TQ/delta-TQ and, among synthetic compounds, TMC2O (6-hydroxy-4,4,7,8-tetramethyl-chroman-2-one) were most effective in decreasing the cyt bc(1) activities. Stopped-flow photometric and low-temperature electron paramagnetic resonance spectroscopic experiments showed for TMC2O an inhibition of electron transfer to cyt c(1) and a modulation of the environment of the Rieske iron-sulfur protein (ISP). Docking experiments suggest a binding interaction of the 6-OH group and 1-O atom/2-C( horizontal lineO) group of TMC2O with Glu-271 (cyt b) and His-161 (ISP) in the cyt bc(1) complex, respectively. This binding pose is similar but not identical to the potent inhibitor stigmatellin. The data suggest that chroman-2-ones are possible templates for modulatory molecules for the cyt bc(1) target.
• 2.82

  Impact points

  Synthesis and characterization of several carbamoyl- and methylcarbamoyl-substituted EMPO derivatives.

  Klaus Stolze, Natascha Rohr-Udilova, Andreas Hofinger, Thomas Rosenau

  Bioorganic & medicinal chemistry. 09/2009;

  The spin trapping behavior of four novel carbamoyl-substituted EMPO derivatives, namely 5-carbamoyl-3,5-dimethyl-pyrroline N-oxide (CADMPO), 3,5-dimethyl-5-methylcarbamoyl-pyrroline N-oxide (DMMCAPO), 5-carbamoyl-3-ethyl-5-methyl-pyrroline N-oxide (CAEMPO), and 3-ethyl-5-methyl-5-methylcarbamoyl-pyr... [more] The spin trapping behavior of four novel carbamoyl-substituted EMPO derivatives, namely 5-carbamoyl-3,5-dimethyl-pyrroline N-oxide (CADMPO), 3,5-dimethyl-5-methylcarbamoyl-pyrroline N-oxide (DMMCAPO), 5-carbamoyl-3-ethyl-5-methyl-pyrroline N-oxide (CAEMPO), and 3-ethyl-5-methyl-5-methylcarbamoyl-pyrroline N-oxide (EMMCAPO), towards different oxygen- and carbon-centered radicals is described, the half lives of the respective superoxide adducts ranging from about 10 to 20min. The most characteristic adducts were, however, formed from methyl, hydroxymethyl, hydroxyethyl, and carbon dioxide anion radicals.
• 4.50

  Impact points

  Synthesis of (13)C-Perlabeled Cellulose with more than 99% Isotopic Enrichment by a Cationic Ring-Opening Polymerization Approach.

  Christian Adelwöhrer, Toshiyuki Takano, Fumiaki Nakatsubo, Thomas Rosenau

  Biomacromolecules. 09/2009;

  (13)C-Perlabeled cellulose was obtained in a seven-step approach from (13)C(6)-labeled d-glucose with a cationic ring-opening polymerization as the key step. Isopropylidene protection, benzylation of the remaining free 3-O-position and subsequent deprotection afforded 3-O-benzyl-(13)C(6)-glucose (2)... [more] (13)C-Perlabeled cellulose was obtained in a seven-step approach from (13)C(6)-labeled d-glucose with a cationic ring-opening polymerization as the key step. Isopropylidene protection, benzylation of the remaining free 3-O-position and subsequent deprotection afforded 3-O-benzyl-(13)C(6)-glucose (2). Regioselective bis-pivaloylation followed by subsequent ortho-esterification provided the precursor for the cationic ring-opening polymerization, 3-O-benzyl-(13)C(6)-glucopyranose 1,2,4-orthopivalate (4). The actual polymerization step gave a stereo- and regioregular (13)C-perlabeled (1-->4)-beta-glucopyranan derivative, which was deprotected into fully labeled (13)C-cellulose, as the cellulose II allomorph with a DP of 40, in an overall 28% yield. All reaction steps were optimized beforehand with nonlabeled compounds toward high yields and high reproducibility and the final compound was comprehensively analytically characterized.

• Precipitation of Hemicelluloses from DMSO/Water Mixtures Using Carbon Dioxide as an Antisolvent

  Haimer Emmerich, Wendland Martin, Potthast Antje, Rosenau Thomas, Liebner Falk

  Journal of Nanomaterials. 01/2009;

  Supercritical antisolvent precipitation is a relatively recent technology which can be used for controlled preparation of polymer particles from solutions. This is done by the addition of an antisolvent to a polymer solution causing supersaturation of the polymer, especially under supercritical cond... [more] Supercritical antisolvent precipitation is a relatively recent technology which can be used for controlled preparation of polymer particles from solutions. This is done by the addition of an antisolvent to a polymer solution causing supersaturation of the polymer, especially under supercritical conditions. The particle size of the precipitates can be adjusted mainly by the rate of supersaturation. Spherical xylan or mannan particles having a narrow particle size distribution were precipitated from hemicellulose solutions in dimethyl-sulfoxide (DMSO) or DMSO/water mixtures by carbon dioxide as an antisolvent. By depending on the type of hemicellulose, the DMSO/H2O ratio, and the precipitation conditions such as pressure and temperature, the resulting particle size can be adjusted within a wide range from less than 0.1 to more than 5 μm. Nano- and microstructured native xylans and mannans as obtained can be used in many applications such as encapsulation of active compounds, slow release agents, or chromatographic separation materials.
• 8.58

  Impact points

  Van der Waals versus hydrogen-bonding forces in a crystalline analog of cellotetraose: cyclohexyl 4'-O-cyclohexyl beta-D-cellobioside cyclohexane solvate.

  Yuko Yoneda, Kurt Mereiter, Christian Jaeger, Lothar Brecker, Paul Kosma, Thomas Rosenau, Alfred French

  Journal of the American Chemical Society. 01/2009; 130(49):16678-90.

  Hydrogen bonding is important in cellulosic and other carbohydrate structures, but the role of interactions between nonpolar groups is less understood. Therefore, we synthesized cyclohexyl 4'-O cyclohexyl beta-D-cellobioside (8), a molecule that has two glucose rings and two nonpolar cyclohexyl ... [more] Hydrogen bonding is important in cellulosic and other carbohydrate structures, but the role of interactions between nonpolar groups is less understood. Therefore, we synthesized cyclohexyl 4'-O cyclohexyl beta-D-cellobioside (8), a molecule that has two glucose rings and two nonpolar cyclohexyl rings. Key to attaching the 4'-Ocyclohexyl group was making the 4'-O,6'-O-cyclohexylidene ketal. After peracetylation, the cyclohexylidene ketal ring was opened regioselectively, providing 65% of 8 after final deacetylation. Comparison of the crystal structure of 8, as the cyclohexane solvate, with those of cellulose and its fragments, especially cellotetraose with four glucose rings, revealed extensive effects from the cyclohexyl groups. Three conformationally unique molecules (A, B, and C) are in the triclinic unit cell of 8, along with two solvent cyclohexanes. When viewed down the crystal's a-axis, the array of C, A, and B looks like the letter N, with A inclined so that its cyclohexyl groups can stack with those of the reducing ends of the B and C molecules. The lower left and upper right points of the N are stacks of cyclohexyl rings on the nonreducing ends of B and C, interspersed with solvent cyclohexanes. Whereas cellotetraose has antiparallel (up-down) packing, A and B in 8 are oriented "down" in the unit cell while C is "up". "Down-down-up" (or, alternatively, "up-up-down") packing is rare for carbohydrates. Other unusual details include 06 in all three staggered orientations: one is tg, two are gg, and three are gt, confirmed with CP/MAS 13C NMR. The tg O6 donates a proton to an intramolecular hydrogen bond to O2', opposite to the major schemes in native cellulose I. A similar but novel O6B-H...O2'B hydrogen bond is based on a slightly distorted gg orientation. The hydrogen bonds between parallel molecules are unique, with linkages between O2'A and O2'B, O3'A and O3'B, and O6A and O6B. Other details, such as the bifurcated O3...O5' and ...O6' hydrogen bonds are similar to those of other cellulosic structures. C-H...O hydrogen bonds are extensive along the [110] line of quarter-staggering. The unusual features described here expand the range of structural motifs to be considered for as-yet undetermined cellulose structures.

• Oxidative modifications of cellulose in the periodate system – Reduction and beta-elimination reactions

  Antje Potthast, Sonja Schiehser, Thomas Rosenau, Mirjana Kostic

  Holzforschung. 01/2009; 63.

  The conversion of cellulose to dialdehyde cellulose (DAC) by treatment with aqueous periodate was studied by the CCOA method, which is a combination of gel permeation chromatography and carbonyl-selective fluorescence labeling. The beta-alkoxy-elimination reaction under alkaline conditions was used ... [more] The conversion of cellulose to dialdehyde cellulose (DAC) by treatment with aqueous periodate was studied by the CCOA method, which is a combination of gel permeation chromatography and carbonyl-selective fluorescence labeling. The beta-alkoxy-elimination reaction under alkaline conditions was used as a diagnostic tool to address the regioselectivity of the oxidation at low degrees of conversion. The oxidation proceeded by random oxidant attack; cluster-like or isolated oxidation patterns were excluded. The beta-alkoxy-elimination proceeded as a competitive process during reduction of DAC by sodium borohydride. Reduction was thus inevitably accompanied by a significant loss in molecular weight. The borohydride treatment decompacted the molecules by reducing the aldehyde groups and destroying hemiacetal crosslinks. As a result, highly flexible chains were produced.
• 2.82

  Impact points

  Spin trapping experiments with different carbamoyl-substituted EMPO derivatives.

  Klaus Stolze, Natascha Rohr-Udilova, Andreas Hofinger, Thomas Rosenau

  Bioorganic & medicinal chemistry. 10/2008; 16(17):8082-9.

  The spin trapping behavior of five carbamoyl-substituted EMPO derivatives, 5-aminocarbonyl-5-methyl-pyrroline N-oxide (CAMPO (AMPO)), 5-aminocarbonyl-5-ethyl-pyrroline N-oxide (CAEPO), 5-aminocarbonyl-5-propyl-pyrroline N-oxide (CAPPO), 5-aminocarbonyl-5-n-butyl-pyrroline N-oxide (CABPO), and 5-amin... [more] The spin trapping behavior of five carbamoyl-substituted EMPO derivatives, 5-aminocarbonyl-5-methyl-pyrroline N-oxide (CAMPO (AMPO)), 5-aminocarbonyl-5-ethyl-pyrroline N-oxide (CAEPO), 5-aminocarbonyl-5-propyl-pyrroline N-oxide (CAPPO), 5-aminocarbonyl-5-n-butyl-pyrroline N-oxide (CABPO), and 5-aminocarbonyl-5-n-pentyl-pyrroline N-oxide (CAPtPO), toward different oxygen- and carbon-centered radicals is described, the stabilities of the superoxide adducts ranging from about 8 to 17min.
• 0.91

  Impact points

  Ubichromanol: A prodrug to support mitochondrial ubiquinone functions?

  Lars Gille, Werner Stamberg, Wolfgang Gregor, Walter Jäger, Gottfried Reznicek, Thomas Netscher, Thomas Rosenau, Hans Nohl

  BioFactors (Oxford, England). 02/2008; 32(1-4):83-90.

  Ubichromanol-9 (UCa_{9}), with a side chain consisting of nine isoprene units) is a reductive cyclization product of ubiquinone-10 (UQ_{10}). It acts as a radical scavenging antioxidant and is about half as effective as alpha-tocopherol. Already decades ago its one-electron oxidation product, the ub... [more] Ubichromanol-9 (UCa_{9}), with a side chain consisting of nine isoprene units) is a reductive cyclization product of ubiquinone-10 (UQ_{10}). It acts as a radical scavenging antioxidant and is about half as effective as alpha-tocopherol. Already decades ago its one-electron oxidation product, the ubichromanoxyl radical had been identified. However, nothing was known so far about the two-electron oxidation product of this antioxidant and its bioactivity. This study proves that ubichromanol can be oxidized to a ubiquinone-like compound with a hydroxyl-substituted side chain (UQ_{10}OH), a metabolite that is naturally present in bovine liver mitochondria. The bioactivity of this ubiquinone derivative in its reduced form as substrate for mitochondrial complex III (cytochrome bc_{1} complex) was slightly below that of native ubiquinol, but significantly higher than that of reduced alpha-tocopheryl quinone. Since ubiquinone-like molecules (UQ_{10}OH, UQ_{10}) were identified as oxidation products of UCa_{9} during lipid peroxidation, this ubiquinone derivative could provide a possibility to combine antioxidant properties of chromanols and bioenergetic benefits of UQ_{10}.

• A Novel Dimer of α-Tocopherol

  Patel Anjan, Mazzini Francesco, Netscher Thomas, Rosenau Thomas

  Research Letters in Organic Chemistry. 01/2008;

  Decomposition of the complex 4, formed between the α-tocopherol ortho-quinone methide (2) and NMMO, by fast heating from −78∘C to 70∘C in inert solvents produces a novel α-tocopherol dimer with 6H,12H-dibenzo[b,f][1,5]dioxocine structure (5) which—in contrast to the well-kn... [more] Decomposition of the complex 4, formed between the α-tocopherol ortho-quinone methide (2) and NMMO, by fast heating from −78∘C to 70∘C in inert solvents produces a novel α-tocopherol dimer with 6H,12H-dibenzo[b,f][1,5]dioxocine structure (5) which—in contrast to the well-known spiro-dimer of α-tocopherol (3)—is symmetrical. This is the first example of a direct reaction of the highly transient zwitterionic, aromatic precursor 2a in the formation of the ortho-quinone methide 2.

• A Novel Dimer of α-Tocopherol

  Patel Anjan, Mazzini Francesco, Netscher Thomas, Rosenau Thomas

  Research Letters in Organic Chemistry. 01/2008;

  Decomposition of the complex 4, formed between the α-tocopherol ortho-quinone methide (2) and NMMO, by fast heating from −78∘C to 70∘C in inert solvents produces a novel α-tocopherol dimer with 6H,12H-dibenzo[b,f][1,5]dioxocine structure (5) which—in contrast to the well-known spiro-dimer of α-tocop... [more] Decomposition of the complex 4, formed between the α-tocopherol ortho-quinone methide (2) and NMMO, by fast heating from −78∘C to 70∘C in inert solvents produces a novel α-tocopherol dimer with 6H,12H-dibenzo[b,f][1,5]dioxocine structure (5) which—in contrast to the well-known spiro-dimer of α-tocopherol (3)—is symmetrical. This is the first example of a direct reaction of the highly transient zwitterionic, aromatic precursor 2a in the formation of the ortho-quinone methide 2.