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71.
Separation of the Diastereomers (6R)- and (6S)-5,6,7,8-Tetrahydro-L -biopterin The mixture of the diastereomers of the tetraacetylderivative IV of (6RS)-5,6,7,8-tetrahydro-L -biopterin could be separated by fractional crystallisation in methanol into the diastereomers IV A and IV B. Hydrolysis with hydrochloric acid gives the pure, diastereomeric, (6R)- and (6S)-5,6,7,8-tetrahydro-L -biopterins. 相似文献
72.
Max Robba Michel Cugnon De Sevricourt Anne-Marie Godard 《Journal of heterocyclic chemistry》1979,16(6):1175-1180
The cleavage of the pyridazine ring of the acyltetrahydro [1] benzofuro [2,3-d] pyridazones was carried out by hydrolysis, alcoholysis or aminolysis reactions and they affect the lactam 3,4-bond. They lead chiefly to benzofuran derivatives with acid, ester, amide or hydrazide groups in the 2-position and eventually an acylated methylhydrazine group in the 3-position. The cyclization reactions of 3-hydrazinomethylbenzofuran-2-carboxylic acid and its derivatives or ethyl 3-bromome thylbenzofuran-2-carboxylate affords tetrahydrobenzofuropyridazones. The nmr spectra were studied. 相似文献
73.
Teh-Chang Chou Holger Lange Rolf Gleiter Tibor Ggh Miroslav Krí Max H. Pfenninger Marian Valentíny Camille Ganter 《Helvetica chimica acta》1995,78(8):2011-2025
Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano ( 4 ), one ethano and one propano ( 5 ), and two propano bridges ( 6 ) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane ( 7 ) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4–6 . 相似文献
74.
Reactions of Ferrocenol and 1,1′-Ferrocendiol with Cyclotriphosphazenes, P3N3F6 and P3N3Cl6 The hexahalogeno-cyclotriphosphazenes, P3N3X6 (X ? F ( 1 a ), Cl ( 1 b )), react with ferrocenol (FcOH) in a molar ratio 1 : 1 to give the ferrocenoxy derivatives, FcO[P3N3X5] (X ? F ( 3 a ), Cl ( 3 b )); in an analogous manner the tetrameric ring P4N4Cl8 ( 2 b ) is converted to FcO[P4N4Cl7] ( 4 b ). 1 Abkürzungen: Fc = Ferrocenyl, (C5H5)Fe(C5H4?); fc = 1,1′-ferrocendiyl, Fe(C5H4?)2; rc = 1,1′-ruthenocendiyl, Ru(C5H4?)2. Fluorphosphazene werden mit a , Chlorphosphazene mit b gekennzeichnet. With 1,1′-ferrocenediol, (fc(OH) 2 ), the cyclo triphosphazenes react in a molar ratio 1 : 1 to produce fcO 2 [P 3 N 3 X 4 ] (X ? F ( 5 a ), Cl ( 5 b )). According to the x-ray structure analysis, the 1,1′-ferrocenediolato group in 5 a , b is bound to two different phosphorus atoms. On the contrary, the 1,1′-ferrocenedithiolato- and 1,1′-ferrocenediselenolato units in fcS 2 [P 3 N 3 X 5 ] (X ? F ( 6 a ), Cl ( 6 b )) and fcSe 2 [P 3 N 3 X 5 ] (X ? F ( 7 a ), Cl ( 7 b )) are attached to only one phosphorus atom, and spirocyclic 1,3-dichalcogena-2-phospha-[3]ferrocenophanes are formed. All new products have been characterized on the basis of their 1 H, 13 C and 31 P NMR as well as EI mass spectra. The molecular structures of 5 a , b and 6 a have been determined by x-ray structure analyses. 相似文献
75.
Brown crystals of [PMePh3]2[TeBr6(SeBr2)2] ( 1 ) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr6(SeBr2)2]2— anion contains a nearly regular [TeBr6] octahedron where the four equatorial bromo ligands each have developed a bond to the SeII atom of a SeBr2 molecule. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The TeIV—Br distances are in the range 2.67—2.72Å, and the SeII—Br bond lengths in coordinated SeBr2 molecules in the range 2.33—2.34Å. 相似文献
76.
Esam Khalifa Hans-Jürg Furrer Jost H. Bieri Max Viscontini 《Helvetica chimica acta》1978,61(7):2739-2743
Regiospecific deuteriation of folic acid Introduction of a nitroso function at the N (10)-position of folic acid activates the C(9)-hydrogen atoms in such a way, that the exchange of H with D at this position, in NaOD-solution, is extremely facilitated. This fact is utilized in the synthesis of 9,9-dideuterio-folic acid (IV), 7,9,9-trideuterio-folic acid (VII) and 7-deuterio-folic acid (IX). These three products are necessary for the 1H-NMR.-spectroscopical determination of the conformation of 5,6,7,8-tetrahydrofolic acid and its derivatives. 相似文献
77.
Max Ziegler und Hans -Georg Horn 《Fresenius' Journal of Analytical Chemistry》1959,166(5):362-364
Zusammenfassung Aus einem Gemisch von Molybdän- und Vanadyl-thioglykolat wird beim pH-Wert 2 der Molybdänkomplex als Tributylammoniumsalz mit Methylenchlorid selektiv extrahiert. Das Molybdän läßt sich nach erfolgter Teilveraschung des Eindampfrückstands der nichtwäßrigen Phase als Bleimolybdat bestimmen.Herrn Prof. Dr. O. Glemser, Direktor des Anorganisch-Cliemischen Instituts der Universität Göttingen, danken wir für die Unterstützung der Arbeit durch Institutsmittel. — Dem Herrn Bundesminister für Atomkernenergie und Wasserwirtschaft sowie der Deutschen Forschungsgemeinschaft danken wir sehr für ihre Unterstützung. 相似文献
78.
Lahboub Bouyazza Jean-Charles Lancelot Sylvain Rault Max Robba Marie Anne Quermonne 《Journal of heterocyclic chemistry》1991,28(2):373-377
Cyclization of 2-(1-pyrrolyl)piperonylcarboxamide derivatives gave iminium perchlorates which afforded 9-(N-substituted-imino) and 9-(N-substituted amino)-6,7-methylenedioxypyrrolo[1,2-a]indoles. 相似文献
79.
Max F. Bechtold Walter Mahler Robert A. Schunn 《Journal of polymer science. Part A, Polymer chemistry》1980,18(9):2823-2855
Linear relationships among molecular weight, polymerization time, and gelation for the condensation of any monomer, including those of unknown size and functionality, are developed and applied to data on soluble silicic acids generated from tetraethyl silicate and from sodium silicate. The results suggest the formation of monomers containing ca. 12–15 ? OSi units with functionality of ca. 2.05 that condense with a rate constant of ca. 10?4 liter/mole sec and an activation energy of 40–70 kJ/mole. One model compatible with these characteristics and the stoichiometry involved is a ladder polymer ca. 3 ? SiO units wide. Polymer isolation was achieved by replacing residual ? OH with (CH3)3Sio? , as well as by freezing of of aqueous solutions, which yielded fibers under special conditions. Solutions of the uncapped and capped polymers and melts of the latter had low viscosity even for fractions with M?n ~100,000. This implies a coiled or globular nature for the polymers, which is supported by their limited propensity for film and fiber formation. Attemps to improve this situation by copolymerization, the use of other capping agents, and by the polymerization of precapped monomers were unsuccessful. 相似文献
80.
Anthony D. Wright Gabriele M. Knig Otto Sticher Paolo Lubini Patrick Hofmann Max Dobler 《Helvetica chimica acta》1991,74(8):1801-1807
Reinvestigation of the brown alga Dictyota pardalis f. pseudohamata CRIBB led to the crystallization of 1 and to the isolation of the two new dolabellane derivatives 2 and 3 . X-Ray analysis of 1 and 2 , together with detailed 1D-and 2D-NMR studies on 2 and 3 , allowed their structures to be elucidated as (1R*,3S*,7S*,11R*,4Z)-dolabella-4,8(17), 12(18)-triene-3,7-diol ( 1 ), (1R*,3S*,4S*,7S*,8S*,11R*,14R*,12E)-3,4:7,8-diepoxydolabe11-12-ene-14, 18-diol ( 2 ), and (1R*,3S*,4S*,7S*,8S*,11R*,14R*)-3,4:7,8-diepoxy-l,4,8,12,12-pentamethylbicyclo[9. 3. 0]tetra-decan-14-ol( 3 ). 相似文献