Das Werk ist urheberredttlidt gesdtUtzt. Die dadurch begriindeten Rechte, insbesondere die der Db... more Das Werk ist urheberredttlidt gesdtUtzt. Die dadurch begriindeten Rechte, insbesondere die der Dbersetzung, des Nadtdruckes, der Entnahme von Abbildungen, der Funksendung, der Wiedergabe auf photomechanischem oder ahnlichem Wege und der Speicherung in Datenverarbeitungsanlagen, bleiben, auch bei nur auszugsweiser Verwertung, vorbehalten.
Proceedings of the National Academy of Sciences, 2010
Organic biomolecules that have retained their basic chemical structures over geological periods (... more Organic biomolecules that have retained their basic chemical structures over geological periods (molecular fossils) occur in a wide range of geological samples and provide valuable paleobiological, paleoenvironmental, and geochemical information not attainable from other sources. In rare cases, such compounds are even preserved with their specific functional groups and still occur within the organisms that produced them, providing direct information on the biochemical inventory of extinct organisms and their possible evolutionary relationships. Here we report the discovery of an exceptional group of boron-containing compounds, the borolithochromes, causing the distinct pink coloration of well-preserved specimens of the Jurassic red alga Solenopora jurassica . The borolithochromes are characterized as complicated spiroborates (boric acid esters) with two phenolic moieties as boron ligands, representing a unique class of fossil organic pigments. The chiroptical properties of the pigme...
Unsymmetriseh substituierte Ferrocene sind ehirM und k6nnen daher optisch aktiv erhMten werdenL 1... more Unsymmetriseh substituierte Ferrocene sind ehirM und k6nnen daher optisch aktiv erhMten werdenL 1965 haben wir crstmals fiber die Ermittlung der absoluten Konfiguration eines Ferrocenderivates [(+)-1] beriehtet 2. Dazu wurde Horeaus Methode der kinetisehen R~eematspaltung yon racem. ~-Phenylbutterss auf das yon (q-)-I abgeleitete exo-C~rbinol angewendet. Wie sp/iter dann aa anderen Ferroeenen, wie Methylderivatea yon 1 (vgl. 2) 3 und an verwandten Metalloeen-ketonen 1, 4 gezeigt werden konnte, is~ diese ernpirische Methode in der Metallocenreihe genauso verla.81ieh anwendbar, wie bei viele~ anderen Stoffklassen (z. B. Aryl-Mkyl-earbinolen !) *. Sparer wurden dann die (+)-Me~hyl-~-und-~-ferrocenearbons/~uren (3, 4) fiber (-)-7 eindeutig miteinander ehemisch verkn~ipR~; das dabei * Ein k~irzlich erhobener Einwand ~, die Horeaumethode w/~re bier unverliif31ich, well es sioh bei der vorliegenden Aeylierung ,,nicht um Paa.re korrespondierender l~eaktionen" h~ndeR, ist nach den Ergebnissen (s. auch unter~) nieht relevant; die Nichtbeschreibbarkeit eines empirischen Zu-sammenh~nges (der Horeausehen Methode) dm'ch einen Formalismus-das stereochemische AnMogiemodell 6 __ kunn ffir die Bra.uehbarkeR oder gar die
ABSTRACT The Syntheses of -(R)-menthyl and ,-bis-(R)-menthyl derivatives2 and3 of hypericin were ... more ABSTRACT The Syntheses of -(R)-menthyl and ,-bis-(R)-menthyl derivatives2 and3 of hypericin were achieved, and the corresponding diastereomers could be separated. The equilibria between the respective diastereomers are slightly displaced in favor of the chromatographically faster moving ones. Kinetic measurements on these easily equilibrating diastereomers of2 and3 provided anArrhenius activation energy for the interconversion barrier between the two propeller conformers of 83 and 89 kJ/mol. It could be shown that the -menthyl residues are of minor relevance to the height of this barrier, as is also the case for thebay hydroxyl ionization and quinone tautomerization equilibria. It was thus concluded that the intrinsic barrier for the propeller conformer enantiomerization of hypericin is in the order of 80 kJ/mol. These results are in accord with those obtained from semiempirical calculations.Nach Synthese der -(R)-Menthyl- und ,-bis-(R)-Menthylderivate2 und3 des Hypericins konnten die entsprechenden Diastereomerenpaare getrennt werden. Die Gleichgewichte sind etwas zugunsten der chromatographisch rascher wandernden Diastereomeren verschoben. Kinetische Messungen an diesen leicht quilibrierenden Diastereomeren von2 und3 fhrten zu einerArrheniusschen Aktivierungsenergie fr die Interkonversionsbarriere zwischen den beiden Propellerkonformeren von 83 und 89 kJ/mol. Es konnte gezeigt werden, da die -Menthylreste fr die Hhe dieser Barriere nur geringfgige Bedeutung haben, ebenso wie dasbay-Hydroxyl-Ionisierungsgleichgewicht und das Tautomeriegleichgewicht. Daraus wurde geschlossen, da die intrinsische Barriere fr die Enantiomerisierung der beiden Hypericinpropellerkonformeren in der Grenordung von 80 kJ/mol liegt. Dieses Resultat stimmt mit den Ergebnissen semiempirischer Rechnungen berein.
Stereochemistry and tautomerism of stentorin, isostentorin, and fringelit D were investigated usi... more Stereochemistry and tautomerism of stentorin, isostentorin, and fringelit D were investigated using an MM2 derived force field method. For these pigments, the 7,14-dioxo tautomers were derived to be the most stable ones, with a gap of about 50 kJ/mol separating them from the less stable species. The three quinones display propeller and double butterfly conformers. The double butterfly conformers were found to be slightly more stable than the propeller conformers. Compared to hypericin the interconversion barriers between these conformers and between enantiomeric conformers of the same type are lower. They were estimated to be in the order of 40 k J/tool; thus an isolation of enantiomers is improbable.
The charge densities on the nitrogen atoms of symmetrically substituted dipyrromethenes, porphins... more The charge densities on the nitrogen atoms of symmetrically substituted dipyrromethenes, porphins, chlorins and bacteriochlorins were determined by X-ray photoelectron spectroscopy of the N1s-levels. Calculation by means of a p-electron- and an all-valence-electron-method (SCF-LCAO-MO-PPP and CNDO/2) reveals good correlation of both methods with experiment. Both are comparable in predicting the energy of the highest occupied orbitals which were studied by
Using an MM2 derived force field the stereochemistry and tautomerism of isohypericin and several ... more Using an MM2 derived force field the stereochemistry and tautomerism of isohypericin and several bromohypericines, including gymnochrome D and isogymnochrome D, were investigated. The geometries of the "propeller" and "double butterfly" conformers of isohypericin were similar to those of hypericin. However, an interconversion barrier between the enantiomeric "propeller" conformers was found, which was 53kJ/mol lower in isohypericin. From the ten tautomers of isohypericin the 7,14-dioxo tautomer was calculated to be the most stable one by about 50kJ/mol. In the bromo derivatives and the gymnochromes the bromine substituents caused a ruffling of the biaryl fragments. The buttressing effect of the bromine led to an enhancement of the interconversion barriers between enantiomeric conformers. The "double butterfly" conformer was found to be more stable than the "propeller" conformer for tetrabromohypericin and the gymnochromes.
On treating xanthobilirubic acid methyl ester with bromine in methanol, a red bile pigment, which... more On treating xanthobilirubic acid methyl ester with bromine in methanol, a red bile pigment, which was assigned the hitherto unknown 16,24-dehydrobiladiene-ab constitution, is obtained in 20% yield. In addition, the corresponding mesobiliverdin-XIIIa, mesobilirubin-XIIIa, 14-formyl-tripyrrinone, and two diastereomeric 15,16-dimethoxybiladienes-ab could be isolated from the reaction mixture. The mechanistic aspects of this reaction are discussed.
Eine rasche und einfache Bestimmung des Isomerenverhaltnisses sowie die Strukturermittlung von su... more Eine rasche und einfache Bestimmung des Isomerenverhaltnisses sowie die Strukturermittlung von substituierten Methylmetallocenen ist mit Hilfe derKMR-Spektroskopie auf Grund der chemischen Verschiebungen und der relativen Intensitaten der Signale der Ringmethylprotonen moglich.
Die absolute Konfiguration von (+)-1,2-(α-Ketotetramethylen)-ferrocen (Ferroceno[1,2]cyclohexenon... more Die absolute Konfiguration von (+)-1,2-(α-Ketotetramethylen)-ferrocen (Ferroceno[1,2]cyclohexenon) wurde nach Uberfuhrung in dasexo-Carbinol (II) durch kinetische Racematspaltung von α-Phenyl-buttersaureanhydrid (Horeaus Methode) als (R) ermittelt. Eine Zuordnung der Konfigurationen fur die beiden isomeren (cis- bzw.trans-) Bis-(α-ketotetramethylen)-ferrocene war durch Spaltungsversuche moglich. Demnach handelt es sich beim tieferschmelzenden Bis-keton (Schmp. 160°) um das Racemat (trans-) und beim anderen Isomeren (Schmp. 170°) um dieMeso- (cis-) Form. Dem rechtsdrehenden Bis-keton, das in eine linksdrehende Bis-vinylverbindung (IX) uberfuhrbar ist, kommt sehr wahrscheinlich die(R),(R′)-Konfiguration zu.
Summary. A hypericin derivative was synthesized in which instead of the methyl groups two benze... more Summary. A hypericin derivative was synthesized in which instead of the methyl groups two benzene rings were condensed to the chromophoric system in order to extend its conjugation. This derivative showed lowered fluorescence and concomitantly enhanced sensitized production of active oxygen species as compared to hypericin. However, in contrast to intuition its long wavelength band remained unshifted in comparison to its
To screen for organic pigments, like fringelites or porphyrins, in sediments and fossil specimen,... more To screen for organic pigments, like fringelites or porphyrins, in sediments and fossil specimen, a simple diffuse reflectance UV-vis spectroscopic determination was developed. In contrast to common inorganic pigments, like Fe2O3, these pigments exhibit well-structured characteristic absorption peaks which allow their recognition. This method was then used to identify fringelite H in a non-crinoidSolenopora species from the Jurassic. Reflectance FTIR
Journal of Photochemistry and Photobiology B: Biology, 1993
The fluorescence and phosphorescence of hypericin and isohypericin were studied in an ethanol mat... more The fluorescence and phosphorescence of hypericin and isohypericin were studied in an ethanol matrix at 1.2 K. The prompt fluorescence spectra are mirror images of the absorption around the O-O transition, as expected. The O-O vibronic lines of the phosphorescence are found at 13190 and 13622 cm-', and the phosphorescence decay times are 2.79 and 6.6 ms at 1.2 K for hypericin and isohypericin respectively, The fluorescence excitation spectrum of isohypericin reveals a small trace of a different pigment, possibly a tautomeric form of isohypericin. The decay of the phosphorescence of isohypericin is biexponential. The slow component is attributed to an unknown contaminant with a high quantum yield of phosphorescence.
The (Z,Z,Z)-configuration of the mono-lactim-ether of an alkyl substituted bilatriene-abc, Etiobi... more The (Z,Z,Z)-configuration of the mono-lactim-ether of an alkyl substituted bilatriene-abc, Etiobiliverdin-IV-γ, was established for chloroform solutions. Moreover the conformation of this molecule is a helical one (syn-syn-syn) with a twist along the single bonds at the methine groups of approximately 20°. The two tautomeric lactam-forms with a proton on one or the other nitrogen atom of the pyrromethene subsystem are indistin-guishable by the methods used in this investigation: 1H NMR pattern, Lanthanide induced shift technique and Nuclear Overhauser Effect measurements.
Das Werk ist urheberredttlidt gesdtUtzt. Die dadurch begriindeten Rechte, insbesondere die der Db... more Das Werk ist urheberredttlidt gesdtUtzt. Die dadurch begriindeten Rechte, insbesondere die der Dbersetzung, des Nadtdruckes, der Entnahme von Abbildungen, der Funksendung, der Wiedergabe auf photomechanischem oder ahnlichem Wege und der Speicherung in Datenverarbeitungsanlagen, bleiben, auch bei nur auszugsweiser Verwertung, vorbehalten.
Proceedings of the National Academy of Sciences, 2010
Organic biomolecules that have retained their basic chemical structures over geological periods (... more Organic biomolecules that have retained their basic chemical structures over geological periods (molecular fossils) occur in a wide range of geological samples and provide valuable paleobiological, paleoenvironmental, and geochemical information not attainable from other sources. In rare cases, such compounds are even preserved with their specific functional groups and still occur within the organisms that produced them, providing direct information on the biochemical inventory of extinct organisms and their possible evolutionary relationships. Here we report the discovery of an exceptional group of boron-containing compounds, the borolithochromes, causing the distinct pink coloration of well-preserved specimens of the Jurassic red alga Solenopora jurassica . The borolithochromes are characterized as complicated spiroborates (boric acid esters) with two phenolic moieties as boron ligands, representing a unique class of fossil organic pigments. The chiroptical properties of the pigme...
Unsymmetriseh substituierte Ferrocene sind ehirM und k6nnen daher optisch aktiv erhMten werdenL 1... more Unsymmetriseh substituierte Ferrocene sind ehirM und k6nnen daher optisch aktiv erhMten werdenL 1965 haben wir crstmals fiber die Ermittlung der absoluten Konfiguration eines Ferrocenderivates [(+)-1] beriehtet 2. Dazu wurde Horeaus Methode der kinetisehen R~eematspaltung yon racem. ~-Phenylbutterss auf das yon (q-)-I abgeleitete exo-C~rbinol angewendet. Wie sp/iter dann aa anderen Ferroeenen, wie Methylderivatea yon 1 (vgl. 2) 3 und an verwandten Metalloeen-ketonen 1, 4 gezeigt werden konnte, is~ diese ernpirische Methode in der Metallocenreihe genauso verla.81ieh anwendbar, wie bei viele~ anderen Stoffklassen (z. B. Aryl-Mkyl-earbinolen !) *. Sparer wurden dann die (+)-Me~hyl-~-und-~-ferrocenearbons/~uren (3, 4) fiber (-)-7 eindeutig miteinander ehemisch verkn~ipR~; das dabei * Ein k~irzlich erhobener Einwand ~, die Horeaumethode w/~re bier unverliif31ich, well es sioh bei der vorliegenden Aeylierung ,,nicht um Paa.re korrespondierender l~eaktionen" h~ndeR, ist nach den Ergebnissen (s. auch unter~) nieht relevant; die Nichtbeschreibbarkeit eines empirischen Zu-sammenh~nges (der Horeausehen Methode) dm'ch einen Formalismus-das stereochemische AnMogiemodell 6 __ kunn ffir die Bra.uehbarkeR oder gar die
ABSTRACT The Syntheses of -(R)-menthyl and ,-bis-(R)-menthyl derivatives2 and3 of hypericin were ... more ABSTRACT The Syntheses of -(R)-menthyl and ,-bis-(R)-menthyl derivatives2 and3 of hypericin were achieved, and the corresponding diastereomers could be separated. The equilibria between the respective diastereomers are slightly displaced in favor of the chromatographically faster moving ones. Kinetic measurements on these easily equilibrating diastereomers of2 and3 provided anArrhenius activation energy for the interconversion barrier between the two propeller conformers of 83 and 89 kJ/mol. It could be shown that the -menthyl residues are of minor relevance to the height of this barrier, as is also the case for thebay hydroxyl ionization and quinone tautomerization equilibria. It was thus concluded that the intrinsic barrier for the propeller conformer enantiomerization of hypericin is in the order of 80 kJ/mol. These results are in accord with those obtained from semiempirical calculations.Nach Synthese der -(R)-Menthyl- und ,-bis-(R)-Menthylderivate2 und3 des Hypericins konnten die entsprechenden Diastereomerenpaare getrennt werden. Die Gleichgewichte sind etwas zugunsten der chromatographisch rascher wandernden Diastereomeren verschoben. Kinetische Messungen an diesen leicht quilibrierenden Diastereomeren von2 und3 fhrten zu einerArrheniusschen Aktivierungsenergie fr die Interkonversionsbarriere zwischen den beiden Propellerkonformeren von 83 und 89 kJ/mol. Es konnte gezeigt werden, da die -Menthylreste fr die Hhe dieser Barriere nur geringfgige Bedeutung haben, ebenso wie dasbay-Hydroxyl-Ionisierungsgleichgewicht und das Tautomeriegleichgewicht. Daraus wurde geschlossen, da die intrinsische Barriere fr die Enantiomerisierung der beiden Hypericinpropellerkonformeren in der Grenordung von 80 kJ/mol liegt. Dieses Resultat stimmt mit den Ergebnissen semiempirischer Rechnungen berein.
Stereochemistry and tautomerism of stentorin, isostentorin, and fringelit D were investigated usi... more Stereochemistry and tautomerism of stentorin, isostentorin, and fringelit D were investigated using an MM2 derived force field method. For these pigments, the 7,14-dioxo tautomers were derived to be the most stable ones, with a gap of about 50 kJ/mol separating them from the less stable species. The three quinones display propeller and double butterfly conformers. The double butterfly conformers were found to be slightly more stable than the propeller conformers. Compared to hypericin the interconversion barriers between these conformers and between enantiomeric conformers of the same type are lower. They were estimated to be in the order of 40 k J/tool; thus an isolation of enantiomers is improbable.
The charge densities on the nitrogen atoms of symmetrically substituted dipyrromethenes, porphins... more The charge densities on the nitrogen atoms of symmetrically substituted dipyrromethenes, porphins, chlorins and bacteriochlorins were determined by X-ray photoelectron spectroscopy of the N1s-levels. Calculation by means of a p-electron- and an all-valence-electron-method (SCF-LCAO-MO-PPP and CNDO/2) reveals good correlation of both methods with experiment. Both are comparable in predicting the energy of the highest occupied orbitals which were studied by
Using an MM2 derived force field the stereochemistry and tautomerism of isohypericin and several ... more Using an MM2 derived force field the stereochemistry and tautomerism of isohypericin and several bromohypericines, including gymnochrome D and isogymnochrome D, were investigated. The geometries of the "propeller" and "double butterfly" conformers of isohypericin were similar to those of hypericin. However, an interconversion barrier between the enantiomeric "propeller" conformers was found, which was 53kJ/mol lower in isohypericin. From the ten tautomers of isohypericin the 7,14-dioxo tautomer was calculated to be the most stable one by about 50kJ/mol. In the bromo derivatives and the gymnochromes the bromine substituents caused a ruffling of the biaryl fragments. The buttressing effect of the bromine led to an enhancement of the interconversion barriers between enantiomeric conformers. The "double butterfly" conformer was found to be more stable than the "propeller" conformer for tetrabromohypericin and the gymnochromes.
On treating xanthobilirubic acid methyl ester with bromine in methanol, a red bile pigment, which... more On treating xanthobilirubic acid methyl ester with bromine in methanol, a red bile pigment, which was assigned the hitherto unknown 16,24-dehydrobiladiene-ab constitution, is obtained in 20% yield. In addition, the corresponding mesobiliverdin-XIIIa, mesobilirubin-XIIIa, 14-formyl-tripyrrinone, and two diastereomeric 15,16-dimethoxybiladienes-ab could be isolated from the reaction mixture. The mechanistic aspects of this reaction are discussed.
Eine rasche und einfache Bestimmung des Isomerenverhaltnisses sowie die Strukturermittlung von su... more Eine rasche und einfache Bestimmung des Isomerenverhaltnisses sowie die Strukturermittlung von substituierten Methylmetallocenen ist mit Hilfe derKMR-Spektroskopie auf Grund der chemischen Verschiebungen und der relativen Intensitaten der Signale der Ringmethylprotonen moglich.
Die absolute Konfiguration von (+)-1,2-(α-Ketotetramethylen)-ferrocen (Ferroceno[1,2]cyclohexenon... more Die absolute Konfiguration von (+)-1,2-(α-Ketotetramethylen)-ferrocen (Ferroceno[1,2]cyclohexenon) wurde nach Uberfuhrung in dasexo-Carbinol (II) durch kinetische Racematspaltung von α-Phenyl-buttersaureanhydrid (Horeaus Methode) als (R) ermittelt. Eine Zuordnung der Konfigurationen fur die beiden isomeren (cis- bzw.trans-) Bis-(α-ketotetramethylen)-ferrocene war durch Spaltungsversuche moglich. Demnach handelt es sich beim tieferschmelzenden Bis-keton (Schmp. 160°) um das Racemat (trans-) und beim anderen Isomeren (Schmp. 170°) um dieMeso- (cis-) Form. Dem rechtsdrehenden Bis-keton, das in eine linksdrehende Bis-vinylverbindung (IX) uberfuhrbar ist, kommt sehr wahrscheinlich die(R),(R′)-Konfiguration zu.
Summary. A hypericin derivative was synthesized in which instead of the methyl groups two benze... more Summary. A hypericin derivative was synthesized in which instead of the methyl groups two benzene rings were condensed to the chromophoric system in order to extend its conjugation. This derivative showed lowered fluorescence and concomitantly enhanced sensitized production of active oxygen species as compared to hypericin. However, in contrast to intuition its long wavelength band remained unshifted in comparison to its
To screen for organic pigments, like fringelites or porphyrins, in sediments and fossil specimen,... more To screen for organic pigments, like fringelites or porphyrins, in sediments and fossil specimen, a simple diffuse reflectance UV-vis spectroscopic determination was developed. In contrast to common inorganic pigments, like Fe2O3, these pigments exhibit well-structured characteristic absorption peaks which allow their recognition. This method was then used to identify fringelite H in a non-crinoidSolenopora species from the Jurassic. Reflectance FTIR
Journal of Photochemistry and Photobiology B: Biology, 1993
The fluorescence and phosphorescence of hypericin and isohypericin were studied in an ethanol mat... more The fluorescence and phosphorescence of hypericin and isohypericin were studied in an ethanol matrix at 1.2 K. The prompt fluorescence spectra are mirror images of the absorption around the O-O transition, as expected. The O-O vibronic lines of the phosphorescence are found at 13190 and 13622 cm-', and the phosphorescence decay times are 2.79 and 6.6 ms at 1.2 K for hypericin and isohypericin respectively, The fluorescence excitation spectrum of isohypericin reveals a small trace of a different pigment, possibly a tautomeric form of isohypericin. The decay of the phosphorescence of isohypericin is biexponential. The slow component is attributed to an unknown contaminant with a high quantum yield of phosphorescence.
The (Z,Z,Z)-configuration of the mono-lactim-ether of an alkyl substituted bilatriene-abc, Etiobi... more The (Z,Z,Z)-configuration of the mono-lactim-ether of an alkyl substituted bilatriene-abc, Etiobiliverdin-IV-γ, was established for chloroform solutions. Moreover the conformation of this molecule is a helical one (syn-syn-syn) with a twist along the single bonds at the methine groups of approximately 20°. The two tautomeric lactam-forms with a proton on one or the other nitrogen atom of the pyrromethene subsystem are indistin-guishable by the methods used in this investigation: 1H NMR pattern, Lanthanide induced shift technique and Nuclear Overhauser Effect measurements.
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