Beiträge zur Chemie der Pyrrolpigmente, 39. Mitt.: Ein Kraftfeldmodell zur konformationsanalytischen Untersuchung von Gallenfarbstoffen

A force field model was designed with respect to the special needs of bile pigments. It is parametrized and tested using partial structures of bile pigments as well as an integral pigment; the solution structures of the molecules were previously deduced using independent experimental methods.

38. Mitt::Falk, H., Schlederer, T., Wolshann, P., Mh. Chem.112, 199 (1981).     

Beiträge zur Chemie der Pyrrolpigmente, 38. Mitt.: Zur Assoziation von Gallenpigmenten

The long standing problem of solvent dependent absorption spectra of certain bile pigments such as bilirubindimethylester has been solved by measurement of molecular masses by means of vapour pressure osmometry. Using this method and the investigation of the concentration and temperature dependence of the absorption spectra on several model compounds an association equilibrium for pigments of the rubinoid structural type could be confirmed. Moreover the optical properties of the coexisting species and the corresponding equilibrium constants could be deduced by spectroscopic techniques. Verdinoid pigments lacking free carboxylic functions on the other hand tend to be monomeric in solution. A heteroassociated species involving equimolar amounts of a verdinoid and a rubinoid pigment could be verified existing on adsorbents like silicagel.

37. Mitt.:Falk, H., Thirring, K., Tetrahedron, im Druck.     

Beiträge zur Chemie der Pyrrolpigmente, 42. Mitt. Kraftfeldrechnungen an Gallenfarbstoffen: Die Energiehyperfläche rubinoider Pigmente

The energy hypersurface of rubinoid bile pigments is calculated using a force field model previously described. Two cases are observed. I: The pigment is substituted symmetrically or unsymmetrically by apolar groups. This results in a very shallow energy valley containing several enantiomeric conformers of approximately equal energies. II: Substitution by polar groups, especially in position 8 and 12 of the rubin skeleton, (e.g.–CH₂–CH₂–COOH) is followed by a lock in bonding between such groups and the lactam ring functions. Thereby only two enantiomeric conformers, which are energetically stabilized, are possible. The barrier between these species amounts to about 40 kJ/mol. These results are compared with the experimental facts available so far. An analysis of the corresponding energy hypersurfaces of the diastereomeric forms of (Z,Z)-, (E,Z)-, (Z,E)- and (E,E)-configurations is given as well.

41. Mitt.:Falk H., Müller N., Mh. Chem.112, 791 (1981).     

Beiträge zur Chemie der Pyrrolpigmente, 26. Mitt.: Zur anaeroben Photochemie von Gallenpigmenten: Die Lumineszenz von Gallenpigment-Partialstruktursystemen und integralen Farbstoffen

The luminescence properties of about twentyfive model compounds representing the three main partial structures of bile pigments (namely pyrromethenes, pyrromethenones and methylenepyrrolylmethylenepyrrolinones) as well as tripyrrines and the geometrical isomers of aetiobiliverdin-IV- are reported. In these compounds there is usually only a very faint or even no fluorescence and phosphorescene as the pathway of deexcitation. Vibrational internal conversion and photoisomerizations at the exocyclic double bonds are the main anaerobic paths of radiationless decay of the excited states.

H. Falk, K. Grubmayr, E. Haslinger, T. Schlederer undK. Thirring, Mh. Chem.109, 1451 (1978).     

Beiträge zur Chemie der Pyrrolpigmente, 40. Mitt.: Azafulvene,Schlüsselstellen beim Aufbau von Pyrrolpigmenten? —Eine neue Synthese von verdinoiden und rubinoiden Gallenfarbstoffen

Substituted azafulvenes were generated by dehydrogenation of 5-methyl-substituted pyrromethenones withDDQ and characterized by UV- and¹H-NMR-spectroscopy. Their electrophilic properties were demonstrated using several quenchers and furthermore they were used for a synthesis of verdinoid bile pigments (which easily can be converted to rubinoid systems by the action of NaBH₄) with nearly any desired unsymmetrical alkyl substitution patter: The azafulvene spezies was generated by the action ofDDQ on a 5-methylpyrromethenone and was quenched by an 5-unsubstituted pyrromethenone. The resulting rubinoid adduct was dehydrogenated immediatly byDDQ — yields were good to high.

39. Mitt.:Falk, H., Höllbacher, G., Hofer, O., Müller, N., Mh. Chem.112, 391 (1981).     

MO-Berechnungen an Heterocyclen, 19. Mitt.: Zum Einfluß unterschiedlicher Orbitalexponenten für 2 s-und 2 p-STO auf die Sequenz der Orbitalenergien in CNDO-Typ-Rechnungen

CNDO-typ calculations based on a different choice of orbital exponents for 2s- and 2p-STO are able to reproduce almost exactly the order ofHartree-Fock orbital energies from high-accuracyab initio calculations. A uniform symmetry consideration for monocyclic molecules represents a useful method to correlate and compare the results. Some comments are given concerning the interpretation of UPS by means ofKoopmans theorem.

18. Mitt.:G. Kluge, undM. Scholz, Z. Chem., im Druck.     

Umsetzung von Metall- und Metalloidverbindungen mit mehrfunktionellen Molekülen, 22. Mitt.: Die Reaktion von Trimethylsilylcarbonsäureamiden mit Halogen(diorganyl)boranen

Trimethylsilylacetamide and trimethylsilyltrifluoroacetamide react with halogenodiorganylboranes to monomeric or dimeric amidoboranes depending on the organyl substituents. The compounds were characterized analytically and spectroscopically (NMR:¹H,¹⁹F,¹¹B; MS; IR).

21. Mitt.:A. Meller, W. Maringgele, K. Hennemuth undU. Sicker, J. Z. anorg. allg. Chem., im Druck.     

Beiträge zur Chemie der Pyrrolpigmente, 28. Mitt.: Die thermische Stabilität der geometrischen Isomeren von Bilatrienen-abc

In the equilibrium between the two diastereomeric (Z, Z, Z) and (E, Z, Z) forms of aetiobiliverdine-IV- the former is preferred by about 20kJ/mol. For the thermal isomerization a barrier of 108kJ/mol has to be surmounted—as measured for the latter isomer. A value of 12.4 for the logarithm of the preexponential factor leads to a polar singlet mechanism, which was deduced previously for pyrromethenones and arylmethylenepyrrolinones, but a much more positive activation entropy for the verdinoid system indicates a pronounced delocalisation of charge over the entire conjugated system in the corresponding transition state.

27. Mitt.:H. Falk, K. Grubmayr undF. Neufingerl, Mh. Chem.110, 1027 (1979).     

Umsetzungen von Metall- und Metalloidverbindungen mit mehrfunktionellen Molekülen, 16. Mitt.

The reaction of trimethylsilylcarbonamides with halogeno-diorganyl-boranes resp. trihalogenoboranes or organodihalogenoboranes gives monomeric resp. dimeric amidoboranes (borylcarbonamides) and derivatives of 4,8-diaza-1,5-dibora-2,6,9-trioxabicyclo[3.3.1]nonadienes. By reaction of the free acylamides with halogenoboranes in most cases the imide halides could be isolated as the only products. By reaction of the hydrochloride of bis(dimethylamino)-hydroxyborane withn-butyl-lithium followed by addition of the imide halides, the corresponding imidoylamines were formed.¹H,¹¹B, and¹⁹F-nmr spectra, mass spectra and characteristic ir group frequencies are reported.

15. Mitt.:W. Maringgele undA. Meller, Z. anorg. allg. Chem., im Druck.     

Beiträge zur Chemie der Pyrrolpigmente, 27. Mitt.

Pyrromethenones are isomerized into their diastereomers at the exocyclic double bond by light, whereas dipyrromethenes and methylenepyrrolylmethyllenepyrrolinones as well as integral bile pigments containing these two partial structures (biliviolines, biliverdines) are not. The reason for this dichotomy was shown by investigation of model compounds to be neither the thermodynamically and kinetically instable product nor the availability of low states of lone pair character. Instead the very efficient radiationless decay of the excited singlet proceeds via a desactivation process being a tunneling between excited and ground state potential surfaces. Calculations according to this theory ofFormosinho affords quantitative results which are in excellent agreement with experimental data. Another desactivation mode comes from the crossing of the potential surfaces of the ground state of one tautomeric form with those of the excited state of another, leading to a proton transfer process. The molecular basis of these processes is shown to be inter—as well as intramolecular hydrogen bonding.

H. Falk undF. Neufingerl, Mh. Chem.110, 987 (1979).     

Beiträge zur Chemie der Pyrrolpigmente, 32. Mitt.: Zum diagnostischen Wert der13C-Kernresonaz-spektroskopie bei diastereomeren Bilatrienen-abc

All¹³C-NMR signals of (Z, Z, Z)-Aetiobiliverdin-IV- could be assigned to the corresponding positions of the molecular framework using double resonance experiments. In the (Z, Z, E)-isomer the methine carbon signals of the terminal moieties are shifted in a dramatically different manner. Thus they represent an ideal tool for labelling experiments aiming at an experimental support of the photoisomerization hypothesis of the photoreaction of phytochrome.

     

Das Schwingungsspektrum von Barium-Divanadat

The infrared and laser-Raman spectra of crystalline Ba₂V₂O₇ are reported and discussed by means of a Site Symmetry analysis.

28. Mitt. der Reihe Orthovanadate und verwandte Verbindungen. 27. Mitt.:E. J. Baran undM. E. Escobar, J. Phys. Chem. Solids, im Druck; 26. Mitt.:E. J. Baran, I. L. Botto, J. F. Ramos undP. J. Aymonino, Mh. Chem.109, 1139 (1978); 25. Mitt.:E. J. Baran, J. Mol. Struct.48, 441 (1978); 24. Mitt.:E. J. Baran undI. L. Botto, J. inorg. nucl. Chem.40, 1603, (1978); 23. Mitt.:M. E. Escobar undE. J. Baran, Z. Anorg. allg. Chem.,441, 273 (1978).     

Über Reaktionen mit Betain, 13. Mitt.: Darstellung von trihalogenacetyl-methyliden und ihrer Salze aus Betainen

Reaction of the betaine1 and pyridinebetaine8 with trifluoroacetic anhydride yields the salts4a or9a and the yellow ylide5, respectively. In an analogous manner8 reacts with trichloroacetic anhydride to give11a. In a competitive reaction the trifluoroacetates6 and10 are also formed. Pyridinebetaine hydrochloride reacts similarily with trichloroacetic anhydride.

12. Mitt.:Wittmann H., Sobhi D., Petio F. A., Z. Naturf.31 b, 850 (1976).     

Ylide von Heterocyclen,III Pyridinium-Ylide von Malonylheterocyclen

Reaction of isatoic anhydride with the betaine esters2 or3 represents a new synthesis of pyridinium ylides of type5, which have been previously obtained by several other ways. Treatment of the ylide5 with inorganic acids results in the formation of their pyridinium salts5 a–d. Hydrogenation or dehydrogenation of5 with Pd/C give the piperidylquinoline9 or the betaine10, respectively. Both of them can be prepared by an alternative way. ThepK values of some pyridinium ylides were determined.

II. Mitteilung:Kappe Th., Korbuly G., Stadlbauer W., Chem. Ber.111, 3857 (1978).     

Polarographische Untersuchung der Kinetik der Polymerisation von Methylvinylketon

The homogeneous polymerization of methyl-vinyl ketone in diluted methanol solutions in presence of proton donors is studied using the polarographic method. The effect of the cation of the indifferent electrolyte is investigated as well as the influence of small quantities of H₂O. Suggestions were made about the possible mechanisms of these influences in the general scheme of the process proposed byHolleck et al.

     

Beiträge zur Chemie der Pyrrolpigmente, 35. Mitt.: Eine regioselektive,reversible Addition an Bilatriene-abc

Using spectroscopic methods (UV-VIS,¹H-NMR) the reversible addition of donors (alcohols, amines, thiols, HCN, bisulfit and C-H acidic compounds) to bilatrienes-abc was investigated. This equilibrium is in close analogy to the addition of donors to a carbonyl group (as was deduced from thermodynamic and kinetic measurements) and is also the basis for understanding the photochemical isomerization of bilatrienes-abc in the adsorbed state. Based thereon a recipe for the isomerization of bilatrienes-abc in homogeneous phase giving high yields of the (E, Z, Z)-diastereomer is presented; in addition the (E, Z, E)-diastereomer of aetiobiliverdin-IV- was isolated and characterized for the first time. A model compound representing the intramolecular addition of a donor attached to a side chain (mimicking a peptide unit) was synthesized and studied with respect to its photochemical behaviour.

34. Mitt.:H. Falk undK. Thirring, Z. Naturforsch. im Druck.     

Zur Synthese von Human-Big-Gastrin I

The synthesis of the tetratriacontapeptide amide corresponding to the revised primary structure of human big gastrin I is described. For this purpose the fragments were designed in view of the maximum use of those utilized in our previous synthesis of human big gastrin I according to the first sequence proposal. Consequently the key tripeptide-Pro-Pro-His- (sequence 7–9) was prepared in suitably protected form to be used as amino or carboxyl component for assembly of the segments 1–9 and 1–14, respectively. Final condensation of the latter nona- and tetradecapeptide derivatives with the C-terminal segments 10–34 and 15–34 via the azide and the dicyclohexylcarbodiimide/N-hydroxysuccinimide procedure, respectively, leads to crude fully protected human big gastrin I. Upon deprotection by exposure to trifluoroacetic acid in presence of ethanedithiol-(1,2) as scavanger, ion exchange chromatography and partition chromatography, the desired tetratriacontapeptide amide was isolated in satisfactory yield with a high degree of purity. The identical immunological behaviour of the synthetic material, if compared with that of natural human big gastrin I, represents ulterior strong evidence for the correctness of the newly proposed structure for this putative prohormonal form of the gastrins.

Kurzmitteilung:Wünsch E., Wendlberger G., Mladenova-Orlinova L., Göhring W., Jaeger E., Scharf R., Gregory R. A., Dockray G. J., Hoppe-Seyler's Z. Physiol. Chem.362, 179 (1981).     

Hochdruckuntersuchungen zur Löslichkeit von Stickstoff in Wolfram

The paper reports investigations about the solubility of nitrogen in tungsten at nitrogen pressures up to 30 MPa (300 bar). The solubility of nitrogen obeysSieverts' law in the whole pressure range and can be represented by the equation logC _N=1/2 logp _{N 2}+4.0–9520/T (C _N in wt·ppm.p _{N 2} in bar,T in K).

     

Magnetische Eigenschaften von Hf2Fe und Hf2FeH x

The weakly temperature dependent paramagnetic compound Hf₂Fe becomes ferromagnetic by hydrogen absorption, theCurie-temperature of the resulting hydrides depends on the hydrogen content.

     

Die Verteilungskoeffizienten von Dysprosium-, Erbium- und Yttriumnitrat zwischen Tributylphosphat und 8 bis 1M-Salpetersäure

The distribution coefficientsK for Dy-, Er-, and Y-nitrate betweenTBP and 8 to 1M-HNO₃ were determined for a wide range of concentrations.K _Er was higher thanK _Y for the whole range investigated, the separation coefficient reaching its maximum at lowest acidities. The relative place of Dy changed with acidity. On addition of 1M-NH₄NO₃ all distribution coefficients were raised.