Zur Chemie der Pyrrolpigmente, 62. Mitt.

Sixteen diastereomeric 2,3-dihydrobilatrienes-abc substituted in position 3 with various chiral ligands, seven chiral derivatives of a 2,3-dihydrobilatriene-abc-12-propionic acid and a chiral derivative of a 8,12-bilatriene-abc-dipropionic acid were prepared. The chiroptical properties (CD) of these compounds were used as a monitor for the conformational influence of the various ligands. Therefrom it could be deduced that steric effects play a minor role in determining the topology of the chromophore. On the contrary, dipole-dipole interactions of the various partial moments of bile pigments and of the attached ligands crucially influence the conformational situation of the chromophore. This fact may be significant for the stabilization of certain chromophore conformations in biliproteids.

Herrn Prof. Dr.K. Winsauer zum 60. Geburtstag gewidmet.     

Zur Chemie der Selen-Stickstoffverbindungen, 2. Mitt.

Zusammenfassung Darstellung und Eigenschaften von Ammonium-, Kalium-, Silber- und Thalliumsalzen des Triselenimides und der Diimidotriselensäure werden beschrieben, Infrarot-Spektren sowieDebye-Scherrer-Diagramme einiger dieser erstmalig dargestellten Verbindungen werden zu ihrer Charakterisierung mitgeteilt.Mit 3 Abbildungen1. Mitt.:A. Engelbrecht undF. Clementi, Mh. Chem.92, 555 (1961).     

Zur Chemie der Pyrrolpigmente, 56. Mitt.

From an investigation of the ICD of bilatrienes-abc and 2,3-dihydrobilatrienes-abc induced by mixtures of CCl₄ with (+)-cis-Pinane, (–)-lactic and (+)-tartaric acid esters it is concluded that specific interactions between chromophore and the chiral reagents afford a partial resolution of the labile racemate of helices. Attaching chiral residues covalently to the chromophore induces very low resolution of the same kind in case of apolar ligands like a cholesteryl-residue. However, with polar ligands as in the case ofBoc-lysyl derivatives enantiomeric excesses up to 90% are achieved depending on the solvent used.

Herrn Prof. Dr.Karl Schlögl zu seinem 60. Geburtstag gewidmet.     

Zur Chemie der Selen-Stickstoffverbindungen, 3. Mitt.

Zusammenfassung Darstellung und Eigenschaften von Silber- und Kaliumsalzen der Imido-diselensäure werden beschrieben; Infrarot-Spektren sowieDebye-Scherrer-Diagramme dieser erstmalig dargestellten Verbindungen werden zu ihrer Charakterisierung mitgeteilt.Mit 2 Abbildungen     

Zur Chemie der Pyrrolpigmente, 63. Mitt.

Using hexamethylphosphoric acid triamide (HMPT) as solvent for bilatrienesabc and mainly for 2,3-dihydrobilatrienes-abc (which serve as the most suitable models for the biliproteid chromophores) a small hypsochromic shift and a dramatic change of the relative intensities of short and long wavelength absorption bands, as compared to solutions in CCl₄, is observed. Applying NMR-spectroscopic techniques (¹⁵N-,¹³C-,¹H-) a predominance of the (4Z,9E,15Z) diastereomer forming a 5syn-, 10anti-, 14syn-periplanar orclinal conformation is deduced. The stabilisation of this configuration and conformation arises from strong hydrogen bonds between the acidic protons of the bilins andHMPT. Interactions of this kind seem to be the main source of energy to stretch the otherwise coiled bilin chromophore of (4Z,9Z,15Z)-5sp,10sp,14sp geometry. Stretched systems of the type bilin-HMPT may serve as a valuable model for the natural biliproteides.

Herrn Prof. Dr.A. Eschenmoser zum 60. Geburtstag gewidmet.116, 1065 (1985).     

Zur Chemie der Selen-Stickstoffverbindungen, 4. Mitt.

Zusammenfassung Die Anwendung der Zweidimensionalen Papierchromatographie zur Auftrennung der Umsetzungsprodukte von SeO₂F₂ mit NH₃ ermöglichte einen zusammenfassenden Überblick über die gesamten in dieser Reaktion gebildeten Verbindunge. Das hohe Trennvermögen der verwendeten Anordnung gestattete die weitgehende Auftrennung der einzelnen Poly-imido-selensäuren, ihrer Mono- und Diamide, neben den cyclischen Verbindungen Triselenimid und Tetraselenimid. Die Bildung des bisher unbekannten Selensäure-diamides konnte chromatographisch nachgewiesen werden. Ein Vergleich mit den analogen Schwefelverbindungen ergibt bei allgemein sehr ähnlichem Verhalten dennoch einige charakteristische Unterschiede.Mit 1 Abbildung3. Mitt.:A. Engelbrecht, Mh. Chem.92, 1269 (1961).     

Chemie der Seltenerdmetalle, 22. Mitt.*

Zusammenfassung Auf Grund der Löslichkeit des Ce(III)-Malonats in Perchlorsäurelösungen wurden die Dissoziationsgleichgewichte der gebildeten Komplexionen, d. h., von [CeMal ₂]^– und [CeMal]⁺ untersucht. Gleichzeitig wurden auch die Löslichkeitsprodukte des Ce(III)-Malonats, u. zw.: [Ce³⁺]² [Mal ^2–]^3**, [CeMal ⁺]² [Mal ^2–] und [CeMal ⁺] [CeMal _2–] bestimmt.

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Chemistry of the rare earth metals, XXII: Dissociation equilibria of Ce(III)-malonate in weakly acidic solution

The solubility of cerous malonate in perchloric acid solutions was investigated. The dissociation equilibria of the complex ions formed, i.e. [CeMal ₂]^– and [CeMal]⁺ were studied and the solubility products of the cerous malonates, i.e. [Ce³⁺]² [Mal ^2–]³, [CeMal ⁺]² [Mal ^2–] and [CeMal ⁺] [CeMal _2–] determined.

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21. Mitt.:R. Pastorek, Gleichgewichtskonstanten der Komplex-partikeln im sauren Bereich des SystemsLn ³⁺–H₄ Tart–KOH, Acta Univ. Palack., im Druck.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. 44. Trialkoxysilylthioderivate der Permethylpolysilane

Contributions to the Chemistry of Silicon-Sulphur Compounds. 44. Trialkoxysilylthio Derivatives of Permethylpolysilanes By reaction of (RO)₃SiSH · NEt₃ (R = i-Pr, t-Bu) with α,ω-Cl₂(SiMe₂)_n (n = 1, 2, 3, 4, 6) or with 1-Cl(SiMe₂)_nMe (n = 2, 4) trialkoxysilylthio derivatives of polysilanes of the two series α,ω-(RO)₃SiS(SiMe₂)_nSSi(OR)₃ and 1-(RO)₃SiS(SiMe₂)_nMe have been prepared. Some properties of obtained new compounds were given. The resistance of the Si? S bond on protolytic splitting has been characterized by half-life times of the alcoholysis reaction.     

Chemie in der Freskomalerei: Kunst,Computer, Chemie

Prehistoric cave paintings have been conserved for about 15000 to 20000 thousand years. As modern investigations have shown the applied pigments are covered with a surface film of crystallized lime.This is the principle used when fresco‐painting. The pigments are painted on freshly applied, wet lime‐water walls or ceilings. During the process of ripening carbon dioxide is absorbed from atmosphere. Lime mortar is hardening, the pigments dry with the plaster to become a permanent part of brickwork. Though fresco buono (= true fresco)is the most durable technique it depends sensitively on processes of acid‐base‐equilibria. Thus, fresco‐paintings are „in dialogue”︁ with environmental conditions for all times. The physico‐chemical principles of fresco‐painting are discussed and demonstrated.     

Zur Chemie der vicinalen Triketone, 4. Mitt.

o-Halogenated (o,o-dihalogenated) anilines react with phenalenetrione (PT) in boiling xylene or acetic acid to give 7H,8H-naphtho[1.8–bc]phenoxazin-7-one derivatives. The analogous reaction with 2.6-dimethyl-or 2.6-diethyl-aniline in xylene gives oxazepines, while in acetic acid preferential addition of the aniline with the para position to the NH₂-group to the central C=O-group ofPT occurs. It can be shown, that the first step in the ring closure reaction is the formation of semiaminales.Es wird gezeigt, daß Aniline, die in 2-bzw. 2,6-Stellung halogensubstituiert sind, mit Phenalentrion (PT) in Xylol oder Eisessig zu den entsprechenden 7H,8H-Naphtho[1,8–bc]-phenoxazin-7-on-derivaten reagieren. Die analoge Umsetzung mit 2,6-Dimethyl-bzw. 2,6-Diäthyl-anilin in Xylol führt zu Oxazepinen, während in Eisessig bevorzugt Addition des zur NH₂-Gruppe in p-Stellung befindlichen H-Atoms an die mittelständige C=O-Gruppe desPT stattfindet. Es wird experimentell bewiesen, daß diese Ringschlußreaktion über primär gebildete Halbaminale abläuft.

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Herrn Prof. Dr.O. Kratky, Graz, mit besten Wünschen zum 70. Geburtstag gewidmet.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXVIII. Trimethylsilylderivate der Trialkoxysilanthiole

Contributions to the Chemistry of Silicon-Sulphur Compounds. XXVIII. Trimethylsilylderivatives of Trialkoxysilanethiols The reactions of trialkoxysilanethiols and their salts with trimethylchlorosilane and hexamethyldisilazane were investigated. The preparation of trimethyltrialkoxydisilthianes has been described. Some properties of the obtained compounds were given and about their silylation ability has been considered.     

Zur Kenntnis der Chemie der Silazane. IV. Über ein Sulfurylphosphazo-silazan

Trichlorophosphazo-sulphurylchloride. Cl₃P?N? SO₂Cl, reacts with heptamethyldisilazane to yield the Si? N? P compound (I) formulated in ?Inhaltsübersicht”?. (I) reacts with PCl₅ or C₆H₅? PCl₄ forming the known 2,2,2,4,4,4-hexachloro-1,3-di-methylcyclo-diphosphazane(II), accompanied by the compound Cl₃P?N? SO₂Cl and C₆H₅? PCl₂?N? SO₂Cl, respectively, which were detected by means of ³¹P-NMR spectroscopy.     

Zur Chemie der vicinalen Triketone, 3. Mitt.

Zusammenfassung Es wird gezeigt, daß die Struktur der vonNeufville undPechmann als Azomethine formulierten Umsetzungsprodukte von 1,3-Diphenyl-1,2,3-propantrion (DPhPT) mit Anilin nicht zutreffend ist.DPhPT reagiert mit Anilin bzw. p-substit. Anilinen bei 20° zu den entsprechenden Halbaminalen. In sied. Äthanol bilden sich Vollaminale, die in Indolderivate umgelagert werden können.

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The chemistry of vicinal triketones, III: Syntheses of heterocycles, CLXVI

It has been shown, that the reaction products of 1.3-diphenyl-propan-1.2.3-trione (DPhPT) with aniline are not azomethines as proposed byNeufville andPechmann. Aniline and p-substituted anilines give semiaminales withDPhPT at 20°. In boiling ethanol aminales are obtained, these open-chain compounds can be turned to indole derivatives.

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Herrn Prof. Dr.Erich Ziegler, Universität Graz, mit besten Wünschen zum 60. Geburtstag gewidmet.     

Semisynthese. Chemie mit den Molekülen der Natur

In Semisynthesis complex molecules have to be manipulated in a chemoselective, regioselective, and stereoselective fashion, necessitating smart protective group operations and innovative synthesis development. Key are always easily accessible and suitable starting materials, especially intermediates which can be produced by biotechnological processes. An extensive synthetic construction of drug candidates carries high innovative and intellectual property protection potential, hence multistep semi‐ and even total syntheses are an integral part of modern industrial research and drug development. Not a long time ago, the complexity such realized would have been inconceivable, which profoundly illustrates the progress synthesis methodology has made. Semisynthesis always aims more toward focussed application, and hence its scientific contribution mostly cater to the elucidation of molecular correlations. Especially the study of cellular processes and their quantification will be stimulated in the future. Thereby semisynthesis will continue to bridge the key future areas of synthesis research and chemical biology.