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1Author    Klaus Praefcke, Dietmar SchmidtRequires cookie*
 Title    Synthese von eis-und traras-4-Cyanocyclohexanol Synthesis of eis-and Jraws-4-Cyanocyclohexanol  
 Abstract    The synthesis of eis-and £ran«-4-cyanocyclohexanol 2 a and 2 b is described for the first time. Their stereochemistry has been determined by X H NMR spectroscopy. 
  Reference    Z. Naturforsch. 35b, 1451—1454 (1980); eingegangen am 24. Juli 1980 
  Published    1980 
  Keywords    Cyclohexanols, Nitrils, Nitrogen Compounds, Stereochemistry 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-1451.pdf 
 Identifier    ZNB-1980-35b-1451 
 Volume    35 
2Author    Annegret LipkaRequires cookie*
 Title    Darstellung und Kristallstruktur des 2:3-Adduktes von Antimontrichlorid und 4-Phenylpyridin, 2 SbCl3 * 3 (CnH9N) Preparation and Crystal Structure of the 2:3 Adduct of Antimony Trichloride and 4-Phenylpyridine, 2SbCl3 * 3(CnH9N)  
 Abstract    A congruently melting phase of molar ratio 2:3 was identified in the system SbCl3/4-phenylpyridine. The structure consists of two different types of complex units: One SbCl3 molecule is bonded to one 4-phenylpyridine ligand only, whereas the other one forms a complex with two 4-phenylpyridine ligands. The SbCl3 unit in the 1:1 species is pyrami-dally shaped, whereas the SbCl3 unit in the 1:2 species displays a T-shaped geometry. The mean angle between the phenyl and pyridyl planes is 33.3°; mean bond lengths are <Sb-Cl> = 247.6 pm and <Sb-N> = 241.7 pm. 
  Reference    Z. Naturforsch. 38b, 341—346 (1983); eingegangen am 27. September 1982 
  Published    1983 
  Keywords    Antimony Trichloride, Crystal Structure, Stereochemistry 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-0341.pdf 
 Identifier    ZNB-1983-38b-0341 
 Volume    38 
3Author    Karl Peters3, Eva-M Aria Peters3, G.Erhard Bringmannb, O. La, F. SchuppbRequires cookie*
 Title    l,3-Dimethoxy-677- benzo[b]naphtho[l,2-d]pyran-6-thione, a Thionolactone-Bridged Axially Prostereogenic Biaryl  
 Abstract    The title compound was prepared from the cor­ responding " ordinary" oxolactone bridged biaryl using Lawesson's reagent. It crystallizes from di-chloromethane / petroleum ether in the mono­ clinic system, space group P2xla; a = 1115.7(2), 
  Reference    Z. Naturforsch. 51b, 431—432 (1996); received September 9 1995 
  Published    1996 
  Keywords    Crystal Structure, Stereochemistry, Biaryl Coupling 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0431_n.pdf 
 Identifier    ZNB-1996-51b-0431_n 
 Volume    51 
4Author    Requires cookie*
 Title    Zur Stereochemie der Phosphinoxydspaltung von R -Methyl -phenyl-a -naphthyl -allyl-phosphoniumbromid The Stereochemistry of the Phosphine Oxide Cleavage of R-( + )-Methyl-phenyl-a-naphthyl-allyl-phosphonium Bromide  
 Abstract    The stereochemical course of the 'phosphine oxide cleavage' of chiral R-(+)-methyl-phenyl-a-naphthyl-allyl-phosphonium bromide is reported. While the a-naphthyl group is cleaved by alkali with predominant retention of configuration at the central phosphorus atom, the allyl group is split off with predominant inversion. 
  Reference    (Z. Naturforsch. 30b, 119—123 [1975]; eingegangen am 11. September 1974) 
  Published    1975 
  Keywords    Phosphine Oxide Cleavage, Stereochemistry, Chiral Phosphonium Salts 
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 TEI-XML for    default:Reihe_B/30/ZNB-1975-30b-0119.pdf 
 Identifier    ZNB-1975-30b-0119 
 Volume    30 
5Author    Reiner Luckenbach, Wolfgang EndresRequires cookie*
 Title    Stereochemistry of the LiAlHi-induced Fission of the Allyl Group from Chiral Phosphonium Salts  
 Abstract    Retention of configuration at phosphorus is found in the LiAlH4-induced fission of the allyl group from chiral phosphonium salts. 
  Reference    (Z. Naturforsch. 31b, 1011—1012 [1976]; eingegangen am 17. März 1976) 
  Published    1976 
  Keywords    LiAlH4-induced Fission, Stereochemistry, Chiral Phosphonium Salts, Chiral Phosphines 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1011_n.pdf 
 Identifier    ZNB-1976-31b-1011_n 
 Volume    31 
6Author    Egbert Keller, Heinrich VahrenkampRequires cookie*
 Title    Stereochemie der Metall-Metall-Bindung: Darstellung und Struktur von Co2(CO)4C5H5P(CH3)2  
 Abstract    The title complex 4 was prepared from 7?-C3H5Co(CO)3 and »/-C5H5(CO)Co-P(CH3)2H. It completes the series of PR2-and AsR2-bridged homodinuclear complexes C^CO^CsHs-As(CH3)2, Mn2(CO)6C5H5As(CH3)2, and Fe2(CO)5C5H5P(CH3)2. Its crystal structure ana-lysis reveals the systematic variation of the ligand distribution along the series which depends only on the number of ligands present and not on given coordination geometries. The metal-metal bond length in 4 is mainly determined by the stereochemical require-ments of the bridging phosphido ligand. 
  Reference    Z. Naturforsch. 33b, 537—541 (1978); eingegangen am 27. Februar 1978 
  Published    1978 
  Keywords    Dinuclear Complexes, Metal-Metal Bonds, Stereochemistry 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0537.pdf 
 Identifier    ZNB-1978-33b-0537 
 Volume    33 
7Author    Annegret Lipka, Hartmut WunderlichRequires cookie*
 Title    Die Kristallstruktur des l:l-Komplexes von Antimontrichlorid und 2.2'-Bipyridin The Crystal Structure of the 1:1 Complex of Antimony Trichloride and 2,2'-Bipyridine  
 Abstract    The crystal structure of the complex compound of SbCL with a chelating bipyridyl group was determined. Sb(CioH8N2)Cl3 crystallizes in the space group P2i/c with a = 818.9(4), b = 695.8(7), c = 2331.3(12) pm, ß = 103.59(4)° and Z = 4 molecules per unit cell. The SbCL fragment is T-shaped with <Sb-Cl> at 254.7 pm. Taking into account also the N atoms of the chelating 2,2'-bipyridyl group (<Sb-N> = 228.1 pm) and an inter-molecular Sb-Cl contact at 334.0 pm the Sb coordination is distorted octahedral. 
  Reference    Z. Naturforsch. 35b, 1548—1551 (1980); eingegangen am 22. August 1980 
  Published    1980 
  Keywords    Stereochemistry, Crystal Structure, Antimontrichloride, 2, 2'-Bipyridine 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-1548.pdf 
 Identifier    ZNB-1980-35b-1548 
 Volume    35 
8Author    Elmar Flaskamp, -A, Gottfried Zimmermann, »., Gerhard Nonnenmacher, Otto IsaacRequires cookie*
 Title    Untersuchungen zur Charakterisierung des Prochamazulens Matrizin aus Matricaria chamomilla L. Studies on the Characterization of the Chamazulene Precursor Matricine from Matricaria chamomilla L  
 Abstract    The relative configuration of the thermolabile chamazulene precursor matricine has been established by NMR spectrometric studies. The NMR spectral data prove to be consistent with the well-known structure of the chamomile component. On the basis of our results the levorotatory natural substance moreover can be specified stereochemically as (—)-(3S*, 3aR*, 4S*, 9R*, 9aS*, 9bS*)-4-acetoxy -2,3,3a,4,5,9,9a,9b -octahy dro -9 -hydroxy -3,6,9 -trimethy lazuleno [4,5 -b ]furan -2 -one. 
  Reference    Z. Naturforsch. 37b, 508—511 (1982); eingegangen am 24. November 1981 
  Published    1982 
  Keywords    Matricaria chamomilla L, Matricine, NMR Spectra, Stereochemistry 
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 TEI-XML for    default:Reihe_B/37/ZNB-1982-37b-0508.pdf 
 Identifier    ZNB-1982-37b-0508 
 Volume    37 
9Author    Walter Tötsch, Fritz SladkyRequires cookie*
 Title    The Hydrolysis of TeF6  
 Abstract    The stereochemistry of the hydrolysis of tellurium hexafluoride has been followed up by 125 Te NMR spectroscopy for each individual step of replacement of fluorine by a hydroxy group. 
  Reference    Z. Naturforsch. 38b, 1025—1026 (1983); eingegangen am 18. März 1983 
  Published    1983 
  Keywords    Tellurium Hexafluoride, Hydrolysis, Stereochemistry, 125 Te NMR Spectra 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1025_n.pdf 
 Identifier    ZNB-1983-38b-1025_n 
 Volume    38 
10Author    KurtH. Pilgram, LairdH. Gale, GlennE. PollardRequires cookie*
 Title    a-hydroxyphostones  
 Abstract    The addition-cyclocondensation reactions of three /?-hydroxyketones with four dialkyl phosphites gave 2-alkoxy-3-hydroxy-l,2-oxaphospholane-2-oxides ("a-hydroxyphosto-nes") (7), in moderate yields. In the solid state and in solution, these compounds exist as dimers with hydrogen bonding between the hydroxyl group and the phosphoryl oxygen atom of an adjacent molecule. The crystal and molecular structure of 3-hydroxy-2-methoxy-3,5,5-trimethyl-l,2-oxaphospholane-2-oxide (7 a) has been determined by single-crystal X-ray crystallography: C7H15O4P, monoclinic space group P2-l/n, cell dimensions a = 8.087(1) Ä, b = 13.386(2) A, c = 9.306(1) A, V = 1007.4 Ä 3 , Z = 4, final R = 0.052. The five-membered ring is puckered, with the carbon bearing the OH and CH3 groups lying out of the plane of the remaining four atoms in the ring. The doubly bonded oxygen attached to the phosphorus atom and the hydroxyl oxygen are in a cis-relationship. The 0(l)-0(4) intermolecular bond distance of 2.75 Ä suggests hydrogen bonding. The 0(1)-H(1) intermolecular bond distance of 1.97 Ä is consistent with this conclusion. Thorough synthetic studies have been carried out on intramolecular esters of 3-hydroxyalkane (and alkene) phosphonic and phosphinic acids (phosto-nes [1]). For example, dehydration of 3-hydroxy-alkanephosphonic acids gave phostones of general structure 1 [2] (Table I). Similar phostones, 2 and 3, were obtained from the reactions of 1,3-dihalo-alkanes with phosphonites and phosphinites, re-spectively [3]. At elevated temperature, 3-bromo-alkanephosphonates are converted into phostones 4 [4]. Acyl-lactone rearrangement of a-acetyl-a-diethoxyphosphonylbutyrolactone gave 5 [5]. Unsaturated phostones (8) are obtained by dehydration of the corresponding (3-hydroxy-3-phenyl-prop-2-enyl)phosphonic acids [6]. 3-Hy-droxypropenylphosphonates, prepared by catalytic reduction of 3-hydroxy-l-propynyl-phosphonates, cyclocondense to 9 having potent Cholinesterase inhibitory activity [7]. The reaction of dialkyl 1,2-alkadienylphosphonates with halogens [8-10] and sulfenyl chlorides [12] gave 10. In the reaction of 3-methyl-l,2-butadienephos-phonyl di chloride with halogens, unsaturated tetra-halophostones (11), are formed [13]. The chlorina-tion of 2-methyl-2,3,5-hexatriene-4-phosphonyl di-chloride proceeds similarly in the direction of cyclo-dechlorination to form 12 [14]. 
  Reference    Z. Naturforsch. 38b, 1122—1129 (1983); received May 6 1983 
  Published    1983 
  Keywords    X-Ray, Stereochemistry, Hydrogen Bonding, Dimerization 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1122.pdf 
 Identifier    ZNB-1983-38b-1122 
 Volume    38 
11Author    CorneliusG. Kreiter, Michael Kotzian, Ulrich Schubert, Robert Bau, MichaelA. BruckRequires cookie*
 Title    Gehinderte Ligandbewegungen in Übergangsmetallkomplexen, X X II I  
 Abstract    [1] Synthese und dynamisches Verhalten von Dicarbonyl(?7-dien)-bis(trimethyl-phosphan)chrom(O) und Dicarbonyl(iy-dien)-bis(trimethylphosphit)chrom(0) Hindered Ligand Motions in Transition Metal Complexes, X X III [1] Syntheses and Dynamic Behaviour of Dicarbonyl(?7-diene)-bis(trimethylphosphane)-chromium(O) and Dicarbonvl(/;-diene)-bis(trimethylphosphite)chromium(0) C r(C O)2[P(CH3)3]2(/7-diene) (9—14) and C r(C O)2[P(OCH3)3]2(?7-diene) complexes (15—20) were prepared photochemically in high yields from Cr(CO)4[P(CH3)3]2 (1) or C r(C O)4[P(OCH3)3]2 (2), respectively, with the dienes 1,3-butadiene (3), rrans-l,3-pentadiene (4), 2-methyl-l,3-butadiene (5), trans,trans-2,4-hexadiene (6), 2-methyl-l,3-pentadiene (7), and 2-ethyl-l,3-butadiene (8). The stereochemistry of 9—20 was determined by IR and N M R spectroscopy. In the case of dicarbonyl-^-r/ww-l ,3-pentadiene-bis(trimethylphosphane)chromium(0) (10) and the cor­ responding trans,trans-2,4-hexadiene complex 12 the X-ray crystal and molecular structure ana­ lyses confirm the spectroscopic conclusions. The distorted octahedral complexes are obtained exclusively as af-isomers. They show a hindered, degenerate isomerization with an intramolecular mutual exchange of the donor ligands. Trigonal prismatic transition states and distorted octahe­ dral intermediates are appropriate models for the explanation of the degenerate isomerization. The activation barriers for the ligand movement were determined by dynamic 3IP-NMR spectro­ 
  Reference    Z. Naturforsch. 39b, 1553—1564 (1984); eingegangen am 14. Juni 1984 
  Published    1984 
  Keywords    77-Diene Complexes, Syntheses, Stereochemistry, Dynamics 
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 TEI-XML for    default:Reihe_B/39/ZNB-1984-39b-1553.pdf 
 Identifier    ZNB-1984-39b-1553 
 Volume    39 
12Author    Dieter Sellmann+, W. Olfgang Kern, Adelgunde Holzmeier, Georg Pöhlmann, M. Atthias, MollRequires cookie*
 Title    Übergangsmetallkomplexe mit Schwefelliganden, LXVI  
 Abstract    Substitutions-und Additionsreaktionen an Molybdän-und Wolfram-Schwefel-Zentren von |M (Cl)(NO)('S4)], M = Mo, W, mit Thiolaten SR" (R = Me, 'Pr, w Bu, Ph) und PM e3 ('S4'2-= l,2-Bis(2-mercaptophenylthio)ethan(2-)) Transition M etal Complexes with Sulfur Ligands, LXVI* Substitution and A ddition Reactions at M olybdenum and Tungsten Sulfur Centres of [M(Cl)(NO)('S4')], M = M o, W, with Thiolates SR " (R = Me, 'Pr, "Bu, Ph) and PM e3('S4'2~ = l,2-Bis(2-mercaptophenylthio)ethane(2-)) Since substrate addition and elim ination reactions are essential reactions o f metal sulfur centres in oxidoreductases, we investigated the substitution o f chloride in [Mo(C1)(NO)('S4')](1) ('S4'2-= l,2-Bis(2-m ercaptophenylthio)ethane(2-)) [4] and in the anal­ ogous tungsten complex [W (Cl)(NO)('S4')](2). The chloride ligands in 1 and 2 can easily be substituted by thiolates to give [M (SR)(NO)('S4')] (M = M o, R = Me 3a, 'Pr 3b, "Bu 3c, Ph 3d; M = W, R = Me 4 a , Ph 4b). For these substitution reactions an associative mechanism is suggested. The SR~ ligands act probably as o-n four electron donor ligands to give metal centres with an 18 electron configuration as also found in the amido complexes [M o(N R 2)(NO)('S4')] [4]. 1 and 2 react with PM e3 to yield the adducts [M(PMe3)(Cl)(NO)('S4')] (M = Mo 5, W 6), w hose N M R spectra indicate the formation o f two stereoisomers in a ratio o f about 2:3. 
  Reference    Z. Naturforsch. 46b, 1349—1356 (1991); eingegangen am 28. Januar 1991 
  Published    1991 
  Keywords    Sulfur Complexes, Synthesis, Reactions, Stereochemistry, M olybdenum, Tungsten 
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 TEI-XML for    default:Reihe_B/46/ZNB-1991-46b-1349.pdf 
 Identifier    ZNB-1991-46b-1349 
 Volume    46 
13Author    Gerhard Bringmann3, Andreas Wuzika, Olaf Schuppa, Karl Peters13, Eva-Maria PetersbRequires cookie*
 Title    l,3-Di-terf-butyl-6//-benzo[b]naphtho[l,2-d]pyran-6-thione, a Severely Helically Distorted Thionolactone-Bridged Biaryl  
 Abstract    The title compound 2c, a potentially useful synthetic intermediate in stereoselective biaryl synthesis, has been prepared from the oxolactone lc, by treatment with Lawesson's reagent. An X-ray structure analysis reveals its strongly helically distorted structure, the overall molecular distortion even slightly exceeding that of the corresponding oxo compound lc. 
  Reference    Z. Naturforsch. 52b, 355—358 (1997); received October 18 1996 
  Published    1997 
  Keywords    Crystal Structure, Thionolactone, Bridged Biaryl, Biaryl Coupling, Stereochemistry 
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 TEI-XML for    default:Reihe_B/52/ZNB-1997-52b-0355.pdf 
 Identifier    ZNB-1997-52b-0355 
 Volume    52 
14Author    Krystyna Lesiak, WojciechJ. StecRequires cookie*
 Title    The Stereochemistry of P-N Bond Cleavage in the Staudinger -Wittig-type Reaction of 2-Anilido-3,4-dimethyl-5-phenyl-l,3,2-oxazaphospholidine-2-thiones  
 Abstract    Both isomers of 2-anilido-3,4-dimethyl-5-phenyl-l,3,2-oxazaphospholidine-2-thiones (2 a and 2 b) derived from (—)ephedrine were obtained and converted to corresponding 2-thiomethyl derivatives (3 a and 3 b). The Staudinger-Wittig-type reaction of P-N bond cleavage was found to proceed with full retention of configuration at P-atom involved into five-membered ring system. 
  Reference    Z. Naturforsch. 33b, 782—785 (1978); received March 28 1978 
  Published    1978 
  Keywords    1, 3, 2-Oxazaphospholidines, (—)Ephedrine, Thioanilides, Thioesters, Stereochemistry 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0782.pdf 
 Identifier    ZNB-1978-33b-0782 
 Volume    33 
15Author    Franz-Erich Baum, Christian Burschka, WolfdieterA. SchenkRequires cookie*
 Title    Ligandensubstitution an cw  
 Abstract    Mo(CO)2(PPh3)2(MeCN)(f/2-S02), Kristall-und Molekülstruktur von ci5-Mo(CO)2(PMe3)3(i/2-S02) [1] Ligand Substitution at c/s-Mo(CO)2(PPh3)2(M e C N)(77:-S0 2), Crystal and Molecular Structure of d 5-M o(CO)2(PM e3)3(/72-S0 2) [1] M o (C O)2(PPh3)2(MeCN)(?72-SC)2) reacts with a number of unidentate or tridentate phosphines with displacement of both MeCN and PPh3. Mixtures of up to three different isomers are obtained the structures of which are assigned by IR , 'H, 13C, and 31P N M R , and in one case by X-ray crystallography. The results support earlier observations concerning the relationship between the disposition of donor and acceptor ligands around the metal and the bonding mode of SO ; . 
  Reference    Z. Naturforsch. 41b, 1211 (1986); eingegangen am 6. Mai 1986 
  Published    1986 
  Keywords    Molybdenum-Sulfur Dioxide Complexes, Ligand Displacement, Structure, Stereochemistry, Linkage Isomerism 
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 TEI-XML for    default:Reihe_B/41/ZNB-1986-41b-1211.pdf 
 Identifier    ZNB-1986-41b-1211 
 Volume    41 
16Author    Prostereogenic Mo-Centers, Dieter Sellmann+, Franz Grasser, Falk Knoch, M. Atthias, MollRequires cookie*
 Title    Übergangsmetallkomplexe mit Schwefelliganden, LXV  
 Abstract    Diastereospeziflsche Alkylierung von [M o(NO)2(S2')2]2 zu chiralen |M o(N O)2(/RS4')l-Komplexen mit chirotopen und prostereogenen Mo-Zentren** Transition Metal Complexes with Sulfur Ligands, LXV* Diastereospecific Alkylation o f [M o(NO)2('S2')2]2" to Chiral [M o(NO)2('RS4')] Complexes with Chirotopic In order to investigate how chirotopicity and stereogenicity o f metal centers influence the enantioselectivity o f metal centered reactions the stereogenic properties o f metal centers in chiral complexes have to be varied without changing their electronic character. Diastereospe­ cific alkylation o f [M o(N O)2('S2')2]2~ by racemic 1,2-dibromopropane and 1,2-dibromobutane yields the title complexes [M o(N O)2('M eS4')] and [M o(N O)2('EtS4')] that differ from the parent compound [M o(N O)2('S4')] with respect to the stereogenicity o f the metal center and allow fu­ ture investigations o f the question raised above. 
  Reference    Z. Naturforsch. 46b, 1343—1348 (1991); eingegangen am 21. März 1991 
  Published    1991 
  Keywords    M olybdenum Nitrosyl Sulfur Complexes, X -R ay, Diastereospecific Alkylation, Stereochemistry 
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 TEI-XML for    default:Reihe_B/46/ZNB-1991-46b-1343.pdf 
 Identifier    ZNB-1991-46b-1343 
 Volume    46 
17Author    Stefan Fuchs, H. Ubert SchmidbaurRequires cookie*
 Title    Phosphonic Acid Anhydrides [R P 0 2]": Oligomerization and Structure  
 Abstract    The phosphonic acid anhydrides of the general formula [R P 0 2]" have been prepared with R = Me, Et, z-Pr, r-Bu, and Ph from the corresponding phosphonic acids and their chlorides and esters. Mass spectrometric data indicate that the trimers are the dominant oligomers for all five systems. According to their NMR spectra, the methyl and r-butyl compounds have a symmetrical (C3v) structure with equivalent RP groups, while the ethyl, /-propyl and phenyl homologues have the Cs structure with non-equivalent PR groups in the ratio 1:2. 
  Reference    Z. Naturforsch. 50b, 855—858 (1995); received November 11 1994 
  Published    1995 
  Keywords    Organophosphonic Acid Anhydrides, Phosphonic Acid Anhydrides, Stereochemistry, NM R Spectra 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-0855.pdf 
 Identifier    ZNB-1995-50b-0855 
 Volume    50 
18Author    Reiner LuckenbachRequires cookie*
 Title    Zur Stereochemie der Phosphinoxidspaltung chiraler acyclischer Phosphoniumsalze The Stereochemistry of the Phosphine Oxide Cleavage of Chiral Acyclic Phosphonium Salts  
 Abstract    The stereochemistry of the 'phosphine oxide cleavage' of 37 different chiral acyclic quaternary phosphonium salts under various reaction conditions is presented and discussed. Über den sterischen Verlauf der unter der Be-zeichnung "Phosphinoxidspaltung" bekannten Um-setzung quartärer acychscher chiraler Phosphonium-salze mit Alkalihydroxiden zu tertiären Phosphin-oxiden und Kohlenwasserstoffen gemäß der Glei-chung (1) 
  Reference    (Z. Naturforsch. 31b, 1127—1134 [1976]; eingegangen am 20. April 1976) 
  Published    1976 
  Keywords    Chiral Phosphonium Salts, Chiral Phosphine Oxides, Stereochemistry, Phosphine Oxide Cleavage, Phosphorane Intermediates 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1127.pdf 
 Identifier    ZNB-1976-31b-1127 
 Volume    31 
19Author    PaavoH. Hynninen, Gunnel SieversRequires cookie*
 Title    Conformations of Chlorophylls a and a' and their Magnesium-Free Derivatives as Revealed by Circular Dichroism and Proton Magnetic Resonance  
 Abstract    The electronic absorption (UV/VIS), circular dichroism (CD) and proton magnetic resonance (*H NMR) spectra have been recorded for C-l0 epimeric chlorophylls a and a', pheophytins a and a' as well as pheophorbides a and a'. Although the epimers in each pair showed virtually identical UV/VIS spectra, their CD spectra were profoundly different and exhibited opposite signs at most wavelengths in the UV region. The differences were interpreted as arising, in part, from different C-10 configurations, and, in part, from conformational alterations induced by the steric strain in the crowded periphery of the macrocycle. The conformational alterations were also clearly indicated by the X H NMR zJö-values observed for the a,ß and <5 methine protons, the C-10 protons and most methyl group protons of the epimers in each pair. This was considered to imply changes in the geometry of the whole macrocycle. The A 6-values were larger for the Mg-free epimers than for the chlorophyll epimers, which shows that the central Mg-atom makes the macrocycle more rigid. Correlations between the signs of the CD bands and configurations are discussed. 
  Reference    Z. Naturforsch. 36b, 1000—1009 (1981); received May 19 1981 
  Published    1981 
  Keywords    Stereochemistry, Conformational Analysis, Chlorophyll and Pheophytin Epimers, X H NMR Spectra, Circular Dichroism 
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 TEI-XML for    default:Reihe_B/36/ZNB-1981-36b-1000.pdf 
 Identifier    ZNB-1981-36b-1000 
 Volume    36 
20Author    Dieter Hellwinkel, Peter Ittemann, Siegbert BohnetRequires cookie*
 Title    Dibenzo  
 Abstract    [b,g]heterocin-5,7-dione Dibenzo[b.g]heterocine-5,7-diones 
  Reference    Z. Naturforsch. 40b, 858—859 (1985); eingegangen am 13. Februar 1985 
  Published    1985 
  Keywords    Dibenzo[b, g]heterocine-5, 7-diones, Synthesis, NMR Spectra, Stereochemistry, Ring Inversion 
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 TEI-XML for    default:Reihe_B/40/ZNB-1985-40b-0858_n.pdf 
 Identifier    ZNB-1985-40b-0858_n 
 Volume    40