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21Author    Otto Mündt, Heinz Riffel, Gerd Becker, Arndt SimonRequires cookie*
 Title    Element—Element-Bindungen, IV [1] Molekül-und Kristallstruktur des Tetramethyldiphosphans und -diarsans Element—Element Bonds, IV [1] Molecular and Crystal Structure of Tetramethyldiphosphane and -diarsane  
 Abstract    The molecular and crystal structures of the isotypic compounds tetramethyldiphosphane 1 and -diarsane 2 have been determined by single crystal X-ray diffraction (monoclinic; C2/m; Z = 2; 1/2: -155/-144 °C\a = 540.6(2)/555.8(2); b = 1131.0(6)/l 136.7(6); c -602.5(2)/612.8(2) pm;/? = 97.31(3)/95.24(3)°;P-P 221.2(1)/As-As 242.9(1) pm). In accordance with the crystallographically imposed symmetry 2/m, the molecules adopt antiperiplanar conformation. Their crystal structures are closely related to those of the homologues tetramethyldistibane 3 [1] and -dibismuthane 4 [3]. As found for the latter compounds, the E —E units (E = P, As) are also aligned in linear chains, but the intermolecular E---E contacts (P-P 381/As---As 370 pm) do not allow any extended interaction between molecules, which otherwise would result in thermochromic effects. 
  Reference    Z. Naturforsch. 43b, 952—958 (1988); eingegangen am 29. Februar 1988 
  Published    1988 
  Keywords    Tetramethyldiphosphane, Tetramethyldiarsane, Conformation, Molecular Structure, Crystal Structure 
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 TEI-XML for    default:Reihe_B/43/ZNB-1988-43b-0952.pdf 
 Identifier    ZNB-1988-43b-0952 
 Volume    43 
22Author    Alexander Lichtblau, Hans-Dieter Hausen, Wolfgang KaimRequires cookie*
 Title    First Structural Characterization of an Easily Oxidized Derivative o f 1,4-Dihydroquinoxaline  
 Abstract    The first crystal structure analysis o f a 1,4-dihydroquinoxaline is described by example o f the l,4-bis(re/-/-butyldimethylsilyl) derivative. In the solid state, this molecule exhibits a non-planar heterocycle with a dihedral angle o f 156.3° along the N -N axis in the boat-shaped 87r electron ring system. The alkyl groups o f the Si(/er/-Bu)M e2 substituents are arranged as to minimize steric repulsion. Despite the reduced n electron conjugation due to non-planarity, the com pound is oxidized reversibly to an EPR detectable radical cation at -0 .5 9 V vs. ferro­ cene in dichloromethane. However, the second oxidation to the fully aromatic dication is elec-trochemically irreversible. A comparison with previously obtained results illustrates the struc­ tural flexibility o f the non-aromatic 1,4-dihydro-1,4-diazine ring system which is strongly affected by rather weak non-bonded interactions. 
  Reference    Z. Naturforsch. 48b, 713 (1993); eingegangen am 21. Dezember 1992 
  Published    1993 
  Keywords    Heterocycles, Organosilicon Compounds, Crystal Structure, Cyclic Voltammetry, Conformation 
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 TEI-XML for    default:Reihe_B/48/ZNB-1993-48b-0713.pdf 
 Identifier    ZNB-1993-48b-0713 
 Volume    48 
23Author    Steffen Runge, M. Athias, O. SengeRequires cookie*
 Title    Electron Donor-Acceptor Compounds. Synthesis and Structure of 5-(l,4-Benzoquinone-2-yl)-10,15,20-trialkylporphyrins  
 Abstract    A series of 5-(benzoquinone)-10,15,20-trialkylporphyrins was synthesized via cross conden­ sation of the respective aldehydes, 2,5-dimethoxybenzaldehyde and pyrrole followed by de-methylation with BBr3 and oxidation with P b 0 2. This method worked reasonably well for compounds bearing the benzoquinone substituent and butyl, isopropyl, 1 -methylpropyl and 2-ethylpropyl residues (2a-d). The free base porphyrin quinones were converted into the zinc(II) complexes (3a-d) all of which showed remarkable stability for porphyrin quinones. The zinc(II) complex 3c bearing isopropyl residues was investigated by X-ray crystallography and showed a supramolecular structure consisting of polymeric chains facilitated by coordina­ tion of a benzoquinone oxygen to a neighboring zinc(II) center. Attempts to synthesize a 5-(benzoquinone)-10,15,20-tris(terr-butylporphyrin) resulted in the formation of a yellow por-phomethene (4), which could not be oxidized further. A crystal structure analysis of 4, the first for a free base porphomethene, shows an extremely twisted conformation with syn-orientation of the three rm-butyl groups. The results indicate that new methods will have to be developed for the synthesis of nonplanar porphyrin quinones. 
  Reference    Z. Naturforsch. 53b, 1021—1030 (1998); received June 15 1998 
  Published    1998 
  Keywords    Porphyrins, Quinones, Electron Transfer Compounds, Crystal Structure, Conformation 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-1021.pdf 
 Identifier    ZNB-1998-53b-1021 
 Volume    53 
24Author    Steffen Runge3, MathiasO. Senge3, Karin Ruhlandt-SengebRequires cookie*
 Title    5,10,15,20-Tetrakis(diphenylmethyl)porphyrin -A Nonplanar Porphyrin with Intermediate Degree of Ruffling  
 Abstract    The title compound was prepared by condensation of pyrrole and diphenylacetaldehyde in 16% yield. Based on spectroscopic data, the free base porphyrin exhibits a nonplanar macrocycle in solution with a degree of distortion between that of 5,10,15,20-tetracyclohexyl-porphyrin and 5,10,15,20-tetra(r-butyl)porphyrin. A crystal structure determination of the cobalt(II) complex reveals a ruffled macrocycle conformation with an average out-of-plane displacement of the m eso carbon atoms by 0.55 A. 
  Reference    Z. Naturforsch. 54b, 662 (1999); received February 17 1999 
  Published    1999 
  Keywords    Porphyrins, Steric Strain, Cobalt Porphyrins, Crystal Structure, Conformation 
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 TEI-XML for    default:Reihe_B/54/ZNB-1999-54b-0662.pdf 
 Identifier    ZNB-1999-54b-0662 
 Volume    54 
25Author    Hugo Scheer, W. Erner KuferRequires cookie*
 Title    Conformational Studies on C-Phycocyanin from Spirulina platensis  
 Abstract    The chromophore-protein interactions of C-phycocyanin (C-PC) from Spirulina platensis have been studied by following the partial and complete denaturation with UV-Vis spectroscopy. From comparison with published MO calculations, an elongated conformation of the chromophore is sug­ gested for native C-PC, a cyclic one for denatured C-PC. By means of partial denaturation, a step­ wise unfolding of the protein has been demonstrated. The presence of at least two sets of spectro­ scopically different diromophores is suggested from the partial denaturation and low temperature experiments. 
  Reference    (Z. Naturforsch. 32c, 513 [1977]; received April 25 1977) 
  Published    1977 
  Keywords    Bile Pigments, Protein Interaction, Conformation, Denaturation 
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 TEI-XML for    default:Reihe_C/32/ZNC-1977-32c-0513.pdf 
 Identifier    ZNC-1977-32c-0513 
 Volume    32 
26Author    A. O., W.J SRequires cookie*
 Title    Axial Preference of Methylthio Substituent in Dioxaphosphorinanyl Ring System  
 Abstract    The spatial disposition of a 2-methvlthio group in the 4-m ethyl-1,3,2-dioxaphosphorin­ anyl ring system was studied by stereochemical correlation, X H, 13C and 31P NMR. It has been established that a CH3S-group prefers an axial orientation much more strongly than does a m ethoxy group. 
  Reference    (Z. Naturforsch. 30b, 430—436 [1975]; received February 4 1975) 
  Published    1975 
  Keywords    ) 2-Methylthio-l, 3, 2-dioxaphosphorinans, Synthesis, Spectral Characteristics, Conformation 
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 TEI-XML for    default:Reihe_B/30/ZNB-1975-30b-0430.pdf 
 Identifier    ZNB-1975-30b-0430 
 Volume    30 
27Author    M. Biddlestone, R. Keat, H. Rose, D. S. Rycroft, R. A. ShawRequires cookie*
 Title    Stereospecific Four-Bond Phosphorus-Phosphorus Spin Couplings in Phosphazenyl-Phosphazenes  
 Abstract    Four-bond phosphorus-phosphorus cou-pling constants have been measured from the 
  Reference    (Z. Naturforsch. 31b, 1001—1002 [1976]; received March 4 1976) 
  Published    1976 
  Keywords    31 P NMR Spectra, Four-Bond Phosphorus-Phosphorus Coupling, Conformation, Phosphazenylcyclophosphazenes 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1001_n.pdf 
 Identifier    ZNB-1976-31b-1001_n 
 Volume    31 
28Author    Heinz Falk, Karl Grubmayr, Klaus ThirringRequires cookie*
 Title    Beiträge zur Chemie der Pyrrolpigmente, XXIII [1] Die Struktur eines Bilatrien-abc-Derivates im gelösten Zustande On the Chemistry of Pyrrole Pigments, XXIII [1] The Structure of a Bilatriene-abc Derivative in the State of Solution  
 Abstract    The (Z,Z,Z)-configuration of the mono-lactim-ether of an alkyl substituted bilatriene-abc, Etiobiliverdin-IV-y, was established for chloroform solutions. Moreover the confor-mation of this molecule is a helical one (syn-syn-syn) with a twist along the single bonds at the methine groups of approximately 20°. The two tautomeric lactam-forms with a proton on one or the other nitrogen atom of the pyrromethene subsystem are indistin-guishable by the methods used in this investigation: *H NMR pattern, Lanthanide induced shift technique and Nuclear Overhauser Effect measurements. 
  Reference    Z. Naturforsch. 33b, 924—931 (1978); eingegangen am 30. Januar 1978 
  Published    1978 
  Keywords    *H NMR, Lanthanide Shifts, Configuration, Conformation, Tautomeric Equilibrium 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0924.pdf 
 Identifier    ZNB-1978-33b-0924 
 Volume    33 
29Author    Karl Folkers, CyrilY. Bowers, Frank Momany, KlausJ. Friebel, Teresa Kubiak, Joseph MaherRequires cookie*
 Title    Antiovulatory Potency and Conformation of an Antagonist of the Luteinizing Hormone-Releasing Hormone Having Six D-Amino Acids  
 Abstract    Thr 1 ,D-Phe 2 ,D-Trp 3 > 6 ]-LHRH was the model antagonist of LHRH, which was the basis for tho design, synthesis and bioassay of seven peptides having four, five and six D-amino acids, which resulted from three single, three double, and one triple introductions of D-amino acids in positions 4, 5 and 8 of the model. Only the analog with six D-amino acids, [N-Ac-Thr 1 ,D-Phe 2 ,D-Trp 3 ,D-Ser^D-Tyr 5 ,D-Trp 6 ,D-Arg 8 ]-LHRH, had antiovulatory activity which was higher than that of the model antagonist, i.e., 70% antiovulatory activity at 25 //g/rat compared with 50% activity at 50 //g/rat, respectively. Empirical energy calculations gave a conformational structure for [N-Ac-Thr 1 ,D-Phe 2 ,D-Trp 3 , D-Ser 4 ,D-Tyr 5 ,D-Ar£' 6 ,D-Arg 8 ]-LHRH which is similar to that calculated for previous potent antagonists. These results are a basis of new designs of antagonists having D-sub-stituents in up to ten positions toward effective inhibitors of ovulation by the parenteral and oral routes of administration. 
  Reference    Z. Naturforsch. 37b, 872—876 (1982); received February 23 1982 
  Published    1982 
  Keywords    Luteinizing Hormone-Releasing Hormone, Antagonist, Antiovulation, Conformation, Contraception [N-Ac- 
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 TEI-XML for    default:Reihe_B/37/ZNB-1982-37b-0872.pdf 
 Identifier    ZNB-1982-37b-0872 
 Volume    37 
30Author    Gerhard Hägele, Peter Reinemer3, Michael Batzb, DietrichM. OotzRequires cookie*
 Title    Kristallstruktur und molekulare Dynamik eines  
 Abstract    Stereoisomeren von (P,P,P",P"-Tetraphenyl)-l,l,2,2-ethan-tetrakisphosphinsäuretetraisopropylester Crystal Structure and M olecular Dynamics of a Stereoisomer of (P,P',P",P'"-Tetraphenyl)-l,l,2,2-ethane-tetraphosphinic Acid Tetraisopropylester The crystal and molecular structure o f (P,P',P",P"'-tetraphenyl)-1,1,2,2-ethane-tetraphos-phinic acid tetraisopropylester has been determined from single-crystal M oK a diffractometer data. The crystals are monoclinic with space group C2/c, Z = 4, a = 2054.5(9), b = 1189.8(5), c = 1800.8(8) pm, ß = 110.07(3)°. The structure was solved by direct methods and refined to R -0.046. A 250 ps-vacuo-trajectory was calculated using the Molecular Dynamics program G R O M O S. Structural data and M D results are compared to N M R spectroscopic data. A Karplus-type relation was confirmed for coupling constants 3ypp. 
  Reference    Z. Naturforsch. 47b, 725—7 (1992); eingegangen am 31. Juli 1991 
  Published    1992 
  Keywords    Crystal Structure, Conformation, Configuration, M D Analysis, N M R Spectra 
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 TEI-XML for    default:Reihe_B/47/ZNB-1992-47b-0725.pdf 
 Identifier    ZNB-1992-47b-0725 
 Volume    47 
31Author    Z. NaturforschRequires cookie*
 Title    Indium Triiodide Complexes of Bis(diphenyIphosphino)ethane (dppe) and its Disulfide (dppeS2)  
 Abstract    Bis(diphenylphosphino)ethane (dppe) and its disulfide (dppeS2) react with two equivalents of indium triiodide to give high yields of the corresponding 1:2 adducts. According to crys­ tal structure determinations, both compounds are molecular bis-terminal complexes with the ligands in an all-trans conformation. Contrary to previous findings for complexes of the indium trihalides and of G aB r3 and G al3 with ditertiary phosphines in fixed cis-structure [bis(diphenylphosphino)ethene or -benzene], no iodide redistribution is observed to give the ionic species [(dppe)Inl2]+ [InL ]-. The molecular structures are also retained in solution. 
  Reference    (Z. Naturforsch. 54b, 21—25 [1999]; received October 10 1998) 
  Published    1999 
  Keywords    Indium Triiodide, Phosphine Complexes, Phosphine Sulfide Complexes, Conformation, Crystal Structure 
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 TEI-XML for    default:Reihe_B/54/ZNB-1999-54b-0021.pdf 
 Identifier    ZNB-1999-54b-0021 
 Volume    54 
32Author    Ryszard Stolarskia, JaroslawM. Cieslab, David ShugarabRequires cookie*
 Title    Monophosphates and Cyclic Phosphates of Some Antiviral Acyclonucleosides: Synthesis, Conformation and Substrate/Inhibitor Properties in Some Enzyme Systems  
 Abstract    Chemical and enzymatic procedures are described for the synthesis o f the m onophosphates and cyclic phosphates o f the antiviral acyclonucleoside 9-(1,3-dihydroxy-2-propoxym ethyl)-guanine (D H PG), its 3-hydroxymethyl-4-hydroxybutyl analogue, the (/?)-and (S)-epimers o f 9-(3,4-dihydroxybutyl)guanine, and 9-(2,3-dihydroxypropyl)guanine. The structures, and some conform ational features, o f all the foregoing, were determined by 'H and 3IP N M R spectroscopy. Their substrate/inhibitor properties have been examined in several enzyme systems, including ribonucleases, snake venom phosphodiesterase, beef heart and higher plant cyclic nucleotide phosphodiesterases, nuclease P I, and 3'-and 5'-nucleo-tidases. The enzymatic results are considered in relation to the mechanism o f the antiviral ac­ tivity o f the cyclic phosphate o f D H PG . 
  Reference    Z. Naturforsch. 45c, 293 (1990); received October 31 1989 
  Published    1990 
  Keywords    Acyclonucleosides, M onophosphates, Cyclic Phosphates, Conformation, Substrate/Inhibitor Properties 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0293.pdf 
 Identifier    ZNC-1990-45c-0293 
 Volume    45 
33Author    Requires cookie*
 Abstract    M alco lm B id d l e st o n e a n d R o b e rt A. S h a w D epartm ent The title compound was synthesized and its structure determined by X -ra y crystallo­ graphy. The NPPI13 substituent adopts a type I conformation with its nitrogen and phosphorus atom s coplanar w ith the ring. The compound, the first asymm etric 1,3,5-triazine to be crystallographically investi­ gated, shows significant variations in ring bond lengths and angles; these are discussed. 
  Reference    (Z. Naturforsch. 30b, 973—974 [1975]; received August 4 1975) 
  Published    1975 
  Keywords    Asym m etric 1, 3, 5-Triazine, X -ray, Crystal Structure, Conformation, Triphenylphosphazenyl Group 
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 TEI-XML for    default:Reihe_B/30/ZNB-1975-30b-0973_n.pdf 
 Identifier    ZNB-1975-30b-0973_n 
 Volume    30 
34Author    Michael Morr, Ludger Ernst, Lutz GrotjRequires cookie*
 Title    2' ,3' -Dideoxy-3' -C-(phosphonomethyl)adenosine, the Phosphonate Analogue of 2'-Deoxyadenosine 3'-Phosphate  
 Abstract    The title compound 7 is prepared in a five-step synthesis starting from l,2-di-0-acetyl-5-0-benzoyl-3-deoxy-3-0-(diethoxyphosphonomethyl)-/3-D-ribofuranose (2). The preferred conformation of 7 is derived from its X H and 13 C NMR data. 
  Reference    Z. Naturforsch. 38b, 1665—1668 (1983); received July 6 1983 
  Published    1983 
  Keywords    Nucleotide Analogue, Phosphonate, !H NMR Spectra, 13 C NMR Spectra, 31 P NMR Spectra, Conformation 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1665.pdf 
 Identifier    ZNB-1983-38b-1665 
 Volume    38 
35Author    Lech Dudycz, Ryszard Stolarski, Reynaldo Pless, David ShugarRequires cookie*
 Title    A 1H NM R Study of the Syn-Anti Dynamic Equilibrium in Adenine Nucleosides and Nucleotides with the Aid of Some Synthetic Model Analogues with Fixed Conformations  
 Abstract    The syn-anti equilibrium about the glycosidic bond in adenosine and some related analogues was studied by means of *H NMR spectroscopy, with the aid of several model analogues fixed in given conformations either by intramolecular bonding, or by introduction of a bulky substituent. A model unambiguously and exclusively in the syn conformation is 8-(a-hydroxyisopropyl) adenosine; while one fixed in the a n ti conformation is 8,5'-anhydro-8-oxoadenosine. A new analogue, fixed in the high an ti conformation, is 8,2'-0-isopropylidenearabinofuranosyladenine. Several additional new model compounds were synthesized and their properties are described. With the aid of these models, the syn-anti dynamic equilibrium was examined for adenosine and some related compounds in different solvent systems, and the conformer populations evaluated quantitatively. The validity of the procedure applied, and the accuracy of the results, are critically examined, and compared with findings obtained by other procedures. Available literature data on the syn-anti equilibrium in other 8-substituted adenosines are re analyzed in the light of the present results. An analysis is also presented of the interdependence of the various conformational parameters, i. e. conformation about the glycosidic bond and those of the sugar ring and exocyclic carbinol group, in adenosine and 2',3'-0-isopropylideneadenosine. 
  Reference    Z. Naturforsch. 34c, 359 (1979); received November 21 1978 
  Published    1979 
  Keywords    NMR Spectroscopy, Conformation, S yn -A n ti Equilibrium, Purine Nucleosides and Nucleotides, Chemical Syntheses 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0359.pdf 
 Identifier    ZNC-1979-34c-0359 
 Volume    34 
36Author    Reynaldo Pless, Lech Dudycz, Ryszard Stolarski, David ShugarRequires cookie*
 Title    Purine Nucleosides and Nucleotides Unequivocally in the Syn Conformation' .Guanosine and 5-GM P with 8-ter/-Butyl and 8-( ß-Hydroxyisopropyl) Substituents  
  Reference    Z. Naturforsch. 33c, 902 (1978); received July 3 1978 
  Published    1978 
  Keywords    8 -Substituted Purines, Purine Nucleosides, Nucleotides, NMR Spectroscopy, Conformation, S yn -A n ti E quilibrium, 5'-Nucleotidase 
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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0902.pdf 
 Identifier    ZNC-1978-33c-0902 
 Volume    33