On the synthesis of hypericin by oxidative trimethylemodin anthrone and emodin anthrone dimerization: Isohypericin

Summary The base catalyzed oxidative dimerization of emodin anthrone exclusively yields hypericin. However, on oxidative dimerization of trimethylemodinanthrone a mixture of hexamethylhypericin and hexamethylisohypericin was obtained. Chromatographic separation of the hexabenzoyl derivatives was achieved, and by saponification about equal amounts of hypericin and isohypericrin were produced. Isohypericin could be characterized for the first time by its spectroscopic data and its protonation and deprotonationpK _a andpK _a ^* values.

---

Zur Synthese von Hypericin durch oxidative Dimerisierung von Trimethylemodinanthron und Emodinanthron: Isohypericin

Zusammenfassung Die basenkatalysierte oxidative Dimerisierung von Emodinanthron liefert ausschließlich Hypericin. Oxidative Dimerisierung von Trimethylemodinanthron ergibt jedoch ein Gemisch von Hexamethylhypericin und Hexamethylisohypericin. Die Hexabenzoylderivate wurden chromatographisch getrennt, und Hypericin und Isohypericin konnten aus diesen Derivaten durch Verseifung freigesetzt werden. Isohypercin konnte erstmals durch seine spektroskopischen Daten und seine Protonierungs- und Deprotonierungs-pK _aundpK _a ^* -Werte charakterisiert werden.

     

2-Amino-1-cyan-glutaconsäureamid-1-methylester,ein Dimeres des Cyanessigesters und Cyanacetamid

Synthesis of methyl 3-amino-4-carbomyl-2-cyano-2-butenoate is described and2 a classified as a dimer of methyl cyanoacetate and cyanoacetamide. By ammonolysis of the dimer of methyl cyanoacetate with dimethylamine and anilines, resp. the dimethylamide and anilides, resp. (2 b and3 a–j) are obtained. Condensation with salicylaldehyde to the pyrone derivative4 proves the structure of2 a, ring closure reactions in basic or acidic medium yield the pyridones6 a and7 a,b, coupling with diazonium salts the pyridazines8 a–d. The amides2 and the anilides3 show hindered rotation of the enamino- and the amide-group by hydrogen bonds between the nitrogen functions and the ester carbonyl (Z-form). The G values are reported.

     

Über Triäthanolaminkomplexe

Zusammenfassung Kristallstrukturelle Untersuchungen an Zinkchlorid-Triäthanolaminverbindungen haben innermolekulare Triäthanolaminkomplexe mit koordinativer Metall-Stickstoffbindung ergeben. Dieses Resultat kann bei bestimmten Verbindungen verallgemeinert werden.

---

Triethanolamine complexes

Crystal structures of ZnCl₂-triethanolamine compounds have been determined. The triethanolamine complexes contain atrans-anular donor-acceptor bond between metal and nitrogen. It is possible to apply this result to different triethanolamine compounds.

---

---

Mit 4 Abbildungen

---

Nach einem Vortrag auf der 11. Diskussionstagung der Sektion für Kristallkunde der Deutschen Mineralogischen Gesellschaft in Saarbrücken 1970.     

Simple diffuse reflectance UV-vis spectroscopic determination of organic pigments (fringelites) in fossils

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 spectroscopy proved not to be useful for this purpose.     

Recent developments in the maytansinoid antitumor agents

Maytansine and its congeners have been isolated from higher plants, mosses and from an Actinomycete, Actinosynnema pretiosum. Many of these compounds are antitumor agents of extraordinary potency, yet phase II clinical trials with maytansine proved disappointing. The chemistry and biology of maytansinoids has been reviewed repeatedly in the late 1970s and early 1980s; the present review covers new developments in this field during the last two decades. These include the use of maytansinoids as "warheads" in tumor-specific antibodies, preliminary metabolism studies, investigations of their biosynthesis at the biochemical and genetic level, and ecological issues related to the occurrence of such typical microbial metabolites in higher plants.     

Über die Reaktion von Nb3Cl3 mit HCl

On the Reaction of Nb₃Cl₈ with HCl The greenish-blue gas phase which is formed at 500–600°C by reaction of Nb₃Cl₈ with HCl, is caused by an equilibrium reaction, in which small amounts of NbCl₅ and larger amounts of NbCl₄ are formed. This is shown by photometric measurements and by thermodynamic calculations.     

Zur Photochemie von Allylaryläthern. 55. Mitteilung über Photoreaktionen

The photochemical reactions of different allyl aryl ethers (Scheme 3) were investigated in hydrocarbons (Chap. 3.1) and in alcoholic solvents (Chap. 3.2). The composition of the photoproducts depended very much on the nature of the solvent. Irradiation (3–95 h) of different methyl substituted allyl aryl ethers ( 1, 3, 5, 7 and 11 ) with a low pressure mercury lamp (λ_Emiss. = 254 nm; 6 or 15 Watt) under argon (quartz vessel) resulted in the formation of 2-, 3– and 4-substituted phenols, dienones and products of consecutive reactions (Tables 1–4 and 6). The results suggested that all products were formed by homolytic cleavage of the C? O bond in the singlet state of the ethers to intermediate radical-geminates (Scheme 5) followed by radical recombination of the two fragments. No products were formed by concerted processes (Table 5, Schemes 5 and 6). Upon irradiation of allyl aryl ethers lacking alkyl substituents at position 4 ( 1 and 5 ) in protic solvents, mainly 2- and 4-allylated phenols were obtained (Tables 1 and 4); 3-allylated phenols were formed only in small amounts (0.02%). However, in aromatic hydrocarbons or cyclohexane 3-allylated phenols were obtained from 1 , 5 and 11 in significant amounts (3–11%; Tables 1, 4 and 6). E.g., upon irradiation of allyl-2,6-dimethyl-2,4-cyclohexadien-1-one ( 6 ) besides 3- and 4-allyl-2, 6-dimethyl-phenol ( 23 and 24 ). Irradiation of 5 in methanol afforded 23 and 6 only in traces, whereas 24 was the main product.     

The Dynamic Behaviour and NMR Solution structures of complexes of the type (Bisphosphine)(cycloocta-1,5-diene)iridium(I) and the X-ray crystal structure of (cycloocta-1,5-diene)((−)-norphos)iridium(I) hexafluorophosphate

A square-planar coordination geometry was found for the complex [Ir(cod){(?)-norphos}][PF₆] ( 1b [PF₆]; cod = cylcoocta-1,5-diene and (?)-norphos = [(2R,3R)-8-9-10-trinorborn-5-ene-2,3-diyl]bis(diphenylphosphine)) in the solid state by X-ray diffraction. Crystal data: monoclinic, space group P2₁, a = 10.751 (6), b = 18.669(14), c = 12.037(8) Å, β = 114.82(5)°, Z = 2. A total structural assignment including the configurational and conformational aspects of this and the related compounds [Ir(bishosphine)(cod)]X (bisphosphine = (?)-chiraphos = (2S,3S)-2,3-bis(diphenylphosphino)butane and (?)-norphos, X = Cl, CF₃SO₃, or PF₆) was carried out in solution by one- and two-dimensional NMR spectroscopy. The complexes containing the CF₃SO₃^? and PF₆^? anions are four-coordinate cations with square-planar geometry, whereas the chlorides are five-coordinate neutral compounds showing solvent-dependent dynamic behaviour. In toluene, two diastereoisomers of [IrCl(cod){(?)-norphos}] ( 2b ) exist and interconvert slowly at room temperature. This interchange is fast in CDCl₃ solution, and it is likely to involve Cl dissociation and the formation of the cation [Ir(cod){(?)-norphos}]⁺ as an intermediate.     

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.