The (trimetaphosphimato)hafnates and ‐zirconates Na4{Hf4(μ4‐O)(μ‐OH)6[(PO2NH)3]4} · 18 H2O [1, Pa3, a = 22.687(3) Å, Z = 8], Na4{Hf4(μ4‐O)(μ‐OH)6[(PO2NH)3]4} · 21 H2O [2, R3, a = 14.350(2), c = 50.348(10) Å, Z = 6], Na4{Zr4(μ4‐O)(μ‐OH)6[(PO2NH)3]4} · 18 H2O [3, Pa3, a = 22.693(3) Å, Z = 8], and Na4{Zr4(μ4‐O)(μ‐OH)6[(PO2NH)3]4} · 21 H2O [4, R3¯, a = 14.303(2), c = 50.284(10) Å, Z = 6] were obtained by the stoichiometric reaction of HfOCl2 · 8 H2O and ZrOCl2 · 8 H2O with an aqueous solution of Na3(PO2NH)3 · 4 H2O, followed by the diffusion‐controlled addition of methanol. During these reactions compounds 1 and 2, or 3 and 4, crystallized simultaneously and the hafnium and zirconium complexes 1 and 3, as well as 2 and 4, were found to be isostructural and isomorphous. The characteristic structural feature which is central to 1, 2, 3, and 4 is the complex tetranuclear anion {M4(μ4‐O)(μ‐OH)6[(PO2NH)3]4}4− with M = Zr or Hf. The anion consists of five corner‐sharing adamantanoid cages. The central cage, {M4(μ4‐O)(μ‐OH)6}8+, has a tetracoordinated oxygen atom in the middle, and the other cages are formed by the trimetaphosphimate ions acting as tridentate ligands which coordinate to Hf or Zr. The water content of the compounds 1−4 could not be determined unequivocally by chemical analyses since the compounds are always obtained as mixtures of the rhombohedral (2/4) and cubic (1/3) phases. Thermal decomposition of compounds 1−4 starts above 120°C and leads to the formation of HfP2O7 and ZrP2O7/NaZr2(PO4)3, with the evolution of H2O and NH3. DSC measurements gave no evidence that the compounds 1 and 2, or 3 and 4, might be transformed into each other by heating.
N-Acetylstizolobsaureester 5 wurde iiber die N-Chlor-Verbindung 13 in die ct,P-ungesattigten (2)-und (E)-Dehydroderivate 14 und 17 sowie das Isocyclostizolobsaure-Derivat 20 umgesetzt. Auch die Dehydrohalogenierung des 3-Brom-a-pyrons 30 mit Natriumhydrid und Kupfer(1)-iodid ergab die gleichea Produkte in geringer Ausbeute. Bei der Hydrierung der Pyrrol-Doppelbindung in 20 zum Isocyclostizolobsaure-Derivat 10 wurde teilweise auch der Pyronring zum Tetrahydroderivat 27 angegriffen und geoffnet. N-Acetylcyclostizolobsaureester 12 erhalt man schlieDlich bei der Thermolyse des gemischten Malonesters 34 mit der Azidgruppe in 3-Stellung am Pyronring durch eine selektive Esterspaltung und Decarboxylierung des cyclischen Malonesters 36. Eine Kristallstrukturanalyse bestatigt die Konstitution 12, nachdem die Enantiomeren durch Chromatographie an Cellulosetriacetat getrennt werden konnten. Synthesis of Dehydrostizalabic Acid DerivativesThe a,P-unsaturated ( Z ) -and @)-derivatives 14 and 17 as well as the derivativc of isocyclostizolobic acid 20 have been obtained from dimethyl N-acetylstizolobate 5 via the N-chloro compound 13. Dehydrohalogenation of the 3-bromo-a-pyrone 30 with sodium hydride and cuprous iodide resulted in low yields of the same products. During hydrogenation of the pyrrolic double bond in 20 leading to the isocyclostizolobic acid derivative 10, attack at the pyrone ring and formation of the tetrahydro derivative 27 could not be prevented. Dimethyl N-acetylcyclostizolobate 12 is isolated, when the 3-azido pyrone 34 is thermolyzed, and the unsymmetric malonic ester 36 is split and decarboxylated selectively. After resolution of racemic 12 by chromatography on triacetylcellulose, the structure is confirmed by A'-ray diffraction analysis of one of the enantiomers.Stizolobsiiure (4) kommt als ungewohnliche Aminosaure frei in tropischen Bohnen (Stizolobium hassjo)') und Pilzen ( A m a~t i t~ pantherind), muscaria3)) vor und wird in der Biosynthese durch Extradiolspaltung des aromatischen Ringes im Dihydroxyphenylalanin (1, DOPA) uber die Zwischenstufe 2 gebildet4.'). In der roten Huthaut des Fliegenpilzes wurde sie im orangefarbenen Musca-aurin 113) als Betalainfarb~toff~) an Betalaminsaure (3) gebunden entdeckt. Auch die Betalaminslure (3) geht im Stoffwechsel durch Recyclisierung der gleichen Zwischenstufe 2') hervor. Im Zuge der Konstitutionsermittlung anderer Farbstofiompocc)
334ChemInform Abstract The N-acetylstizolobate (Ia) is converted, via the in termediate (Ib), to the (Z)-dehydro derivative (II) which can be in part isomerized to its (E)-isomer (III). Treatment of (II) with tBuOCl and decomposition of the product (V) formed gives rise to the compounds (II), (III), (VI) and a small amount of (IV). Dehydrohalogenation of the bromopyrone (VII) with NaH and CuI results only in low yields of (II), (III), and (IV). The desired compound (IV), however, can be obtained from (VI) by treatment with DBU. During hydrogenation of (IV) the formation of the ring-opened product (IX) cannot be prevented. The compound (XIV) is obtained from the unsym. malonic ester (XIIb) which, in turn, is accessible from the dibromide (X) via the intermediate (XIIa). The structure of (XIV) is confirmed by X-ray analysis of one enantiomer (P21; Z=2) obtained by resolution.
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