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  • 1
    Electronic Resource
    Electronic Resource
    Molecular Dynamics of a Schiff Base Tetramacrocycle Studied by NMR and MD Simulations (2000)
    Springer
    Journal of molecular modeling 6 (2000), S. 119-125 
    Details
    ISSN: 0948-5023
    Keywords: Keywords Macrocycle, Schiff base, NMR, chemical exchange, MD, proton template, ROESY, EXSY
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Schiff base condensation of the pentadentate tetrapodal amine 1 with 2,6-diformyl-4-methylphenol 2 leads in a [3 + 6] condensation to a previously not described macrocycle 3 which shows C 3-symmetry. X-ray analysis shows a truncated cone shape for 3. At T ≥ 100°C, the 1H-ROESY/EXSY spectrum reveals pairwise exchange of corresponding sites, indicative of inversion of the whole molecule in an umbrella-like fashion. Molecular dynamics simulations support this hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010723
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  • 2
    Electronic Resource
    Electronic Resource
    Bis(η4-cycloocta-1,5-diene)rhodium(I) trifluoromethanesulfonate (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. m117-m118 
    Details
    ISSN: 1600-5368
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of the title compound, [Rh(C8H12)2](CF3SO3), consists of [(C8H12)2Rh]+ cations and F3CSO3− anions. The cycloocta-1,5-diene ligands are chelated to the central metal atom to create a coordination geometry about rhodium which is essentially square planar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S1600536801003208
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  • 3
    Electronic Resource
    Electronic Resource
    Rationalizable expectations and sunspot equilibria in an overlapping-generations economy (1997)
    Springer
    Journal of economics 65 (1997), S. 257-277 
    Details
    ISSN: 1617-7134
    Keywords: market uncertainty ; overlapping generations ; rational expectations ; rationalizable expectations ; sunspots ; D51 ; D84 ; D90 ; E21
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract There are two theories for the treatment of market uncertainty: rationalizable expectations and sunspot equilibria. This paper shows how the game-theoretic solution concept of rationalizable expectations can be applied to an overlapping-generations exchange economy. Some general properties of these equilibria are discussed. It is shown that rationalizable-expectations equilibria are the predictions yielded by considering sunspot equilibria in which probability beliefs may differ across individuals. This result allows for a new interpretation of sunspot equilibria and helps to understand their relevance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01226845
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  • 4
    Electronic Resource
    Electronic Resource
    Endogenous superantigen expression controlled by a novel promoter in the MMTV long terminal repeat (1993)
    [s.l.] : Nature Publishing Group
    Nature 364 (1993), S. 154-158 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The long U3 region of the MMTV LTR contains an open reading frame (ORF)3'4, regulatory sequences involved in hormone-responsive gene transcription5-7 and various positive and negative regulatory elements8. As well as encoding endogenous superantigen (Sag)1'2, ORF encodes a negative-acting factor ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/364154a0
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  • 5
    Electronic Resource
    Electronic Resource
    Synthese von 3,3-Bis(alkylthio)-2-(2-thioxo-benzo-2H-1,3-thiazol-3-yl)-acrylsäure-Derivaten und Kristallstruktur des entsprechenden Ethyl 3,3-Bis(methylthio)acrylats (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 359-369 
    Details
    ISSN: 1434-4475
    Keywords: Dithiocarboxylation ; 3,3-Bis(alkylthio)acrylonitriles ; Carbon disulfide ; Ketene dithioacetal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The 3,3-bis(alkylthio)-2-(2-thioxo-benzo-2H-1,3-thiazole-3-yl)acrylonitriles3a–e, the methyl and ethyl acrylates4 and5a–d, respectively, are prepared by dithiocarboxylation of the corresponding derivatives of acetic acid1a–c. The crystal structure of ethyl 3,3-bis(methylthio)-2-(2-thioxo-benzo-2H-1,3-thiazole-3-yl)acrylate5a has been determined by X-ray analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809657
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  • 6
    Electronic Resource
    Electronic Resource
    Chemie polyfunktioneller Molekäle, 130. Mitt. [1]: Rubidium- und Cäsium-bis(diphenylphosphanyl)amid – Synthesen, (18-Krone-6)-Komplexe, Spaltprodukte, Kristallstrukturen und Festkörper-NMR-Spektren (1998)
    Springer
    Monatshefte für Chemie 129 (1998), S. 547-566 
    Details
    ISSN: 1434-4475
    Keywords: Keywords. Alkali metal organophosphanylamide; Rubidium ; phosphorus bonding; Caesium ; carbon bonding; 18-crown-6 complexes; Caesium-phosphorane-iminato complex.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  The metalation of bis(diphenylphosphanyl)amine, HN(PPh2)2 (5), with RbOtBu in the presence of N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDTA (3)) in toluene surprisingly affords the nearly PMDTA free RbN(PPh2)2 (6a). Recrystallization of 6a from tetrahydrofuran (THF) yields RbN(PPh2)2ċ0.5 THF (6b). Compounds 6a, b crystallize in thin needles; however, these are not suitable for X-ray structure analyses. The reactions of 5 with MOtBu (M=Rb, Cs) in the presence of 18-crown-6 in toluene yield the monomeric, pale yellow rubidium and caesium complexes [Rb(18-crown-6)(N(PPh2)2)] (7) and [Cs(18-crown-6)(N(PPh2)2)] (8), respectively. Allowing to stand a solution of 8 in THF for three months at 20°C results in a cleavage product of 8. This is identified as the dimeric yellow complex [(Cs(18-crown-6))2(μ-N*P(H)Ph2)2]ċTHF (9). The source of the hydrogen atom in the bridging phosphorane iminate anion [N*P(H)Ph2]− is uncertain. Compounds 7–9 are structurally characterized by X-ray analyses. These reveal that [N(PPh2)2]− acts as P-ligating chelate in 7, whereas it coordinates the Cs+ as N-donor as well as η2 C-donor with one phenyl group in 8. No phosphorus coordination is observed in 8. The two caesium cations in 9 are two-fold N-bridged by [N*P(H)Ph2]−. The coordination sphere of each caesium atom is completed by a 18-crown-6 ligand. The solid state 13C NMR spectrum of 8 reveals dynamic phenomena (rotation of the 18-crown-6 ligand). In the solid state 31P spectrum of 8, 31P, 31P–J-coupling is observed between the chemically non-equivalent phosphorus sites (J=390 Hz).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00013467
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  • 7
    Electronic Resource
    Electronic Resource
    Chemie polyfunktioneller Moleküle, 132. Mitt. [1]. Synthese und Kristallstruktur paramagnetischen fünffach-koordinierten eines Cobalt(III)-Komplexes ausgehend von Co2(CO)8, Ph2P-N*PPh2-PPh2*N-PPh2 und Lufta (1999)
    Springer
    Monatshefte für Chemie 130 (1999), S. 1419-1430 
    Details
    ISSN: 1434-4475
    Keywords: Keywords. Paramagnetic; Five-fold coordinated trigonal bipyramidal cobalt(III) complex; Crystal structure; Octaphenyl-tetraphospha-diazene; Imido-tetraphenyl-diphosphinate; Octacarbonyldicobalt.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  The reaction of Co2(CO)8 and Ph2P-N*PPh2-PPh2*N-PPh2 (1) in a molar ratio between 1:1 and 1:3 in toluene always leads to the formation of both the yellow by-product [fac-Co(CO)3(Ph2P-N*PPh2-PPh2*N-PPh2-P,P′)] [Co(CO)4] (4) and the red compound [(Co)2(μ-CO)(CO)4(μ-Ph2P-N-PPh2)2] (5) that has already been characterized by spectroscopic data and X-ray analysis. Whereas 4 is obtained as a precipitate, the red compound 5 stays in solution and reacts in presence of air with the remaining ligand 1 in a non-stoichiometrical reaction to the violet cobalt(III) complex [Co(η1-O-PPh2*N-PPh2*O)(η2-O-PPh2*N-PPh2*O)2] (6). The crystal structure of 6 proves a distorted trigonal bipyramidal coordination of the oxygen atoms at the Co(III) ion. Surprisingly, complex 6 shows an unusual paramagnetism according to four unpaired electrons (5.21±0.04 BM).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007060050300
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  • 8
    Electronic Resource
    Electronic Resource
    Crystal structure of ethyl 4-methylthio-3-phenyl-2-thioxo-2,3-dihydro-1,3-oxazole-5-carboxylate (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 237-240 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; 1,3-oxazoline-2-thione ; resonance structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound C13H13NO3S2 crystallizes in the triclinic space group $$P\bar 1$$ (Z=2) with lattice constantsa=8.382(2),b=10.042(2),c=10.134(2) Å, α=119.35(1)°, β=101.40(1)° and γ=90.54(1)°. The interplanar angle between the least squares planes of the 1,3-oxazoline ring and the phenyl ring amounts to 90.2°, thus hindering conjugation between the benzene and heterocyclic system. The observed bond parameters of the five-membered heterocycle suggest a significant contribution from a zwitterionic dipolar limiting structure [38.7(5)%] to the description of this ring system. The particular contributions of the resonance structures were estimated by calculations using the HOSE model on the base of the observed bond lengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665176
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  • 9
    Electronic Resource
    Electronic Resource
    Crystal structures of twoN-substituted 2-thioxo-1,3-dithiole-4-carboxamides (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 463-467 
    Details
    ISSN: 1572-8854
    Keywords: 1,3-dithiole-4-carboxamides ; resonance effect ; short intramolecular S...O contact ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The two closely related compoundsN,N-dimethyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide1 andN-(p-methoxy-phenyl)-N-methyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide2 have been characterized by X-ray crystal structure determination. Crystal data for1: triclinic, $$P\bar 1$$ ,a=6.767(1),b=12.594(2),c=6.648(1) Å, α=101.38(1), β=93.37(2), γ=79.62(1)°,V=546.2 Å3,Z=2. Crystal data for2: monoclinic, Cc,a=19.836(4),b=6.057(1),c=15.860(3) Å, β=127.61(3)°,V=1509.5Å3,Z=4. The molecular structures of1 and2 show remarkable differences concerning the conformational behavior. These differences are related to the nature of the substituents at the nitrogen atom. The presence of an aromatic system in2 leads to an almost planar arrangement of the α-oxoketene dithioacetal moiety. This effect is accompanied by a short intramolecular S...O contact of 2.648(2) Å. In the absence of an aromatic system, as is the case for compound1, neither a resonance effect along the α-oxoketene dithioacetal fragment nor a short S...O distance is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665702
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  • 10
    Electronic Resource
    Electronic Resource
    Comparison of azacyclic urea A-98881 as HIV-1 protease inhibitor with cage dimeric N-benzyl 4-(4-methoxyphenyl)-1,4- dihydropyridine as representative of a novel class of HIV-1 protease inhibitors: A molecular modeling study (1999)
    Springer
    Journal of computer aided molecular design 13 (1999), S. 233-242 
    Details
    ISSN: 1573-4951
    Keywords: centrosymmetry ; CoMFA-Field fit ; GRID ; HIV-1 protease ; X-ray crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The functional groups of cage dimeric N-alkyl substituted 3,5-bis(hydroxymethyl)-4-(4-methoxyphenyl)-1,4-dihydropyridines are similar to those of cyclic and azacyclic ureas that are potent inhibitors of HIV-1 protease of the dihydroxyethylene- and hydroxyethylene type, respectively. In the following study the conformity of common functional groups is investigated concerning their orientation in space as well as in the enzyme HIV-1 protease. Starting from X-ray crystal data of the centrosymmetric cage dimeric N-benzyl derivative with ester groups, the derivative with hydroxymethylene groups was built and a systematic conformational search was performed for the conformationally important torsion angles considering electrostatic and van der Waals interactions. From the huge number of conformations those comprising centrosymmetrical and C2-symmetrical energy minima were selected and minimized. The three remaining conformers were fitted to the azacyclic urea A-98881 selected from the HIV-1 protease enzyme- inhibitor complex using the centroids of the corresponding aromatic residues and additionally by the field fit option of the Advanced CoMFA module of SYBYL. Interestingly, the energetically most favourable one, which, additionally, possesses C2-symmetry like the active site cavity of HIV-1 protease, showed the best fit. Comparing the electrostatic potential (EP) of the latter with the EP of A-98881 the aromatic residues show excellent accordance. Slight differences in the extent of the EP were found in the areas of the hydroxymethylene groups of the cage dimer and the single hydroxy group as well as the urea carbonyl group of A- 98881, respectively. In order to compare the binding possibilities to the enzyme HIV-1 protease for the cage dimer and A-98881, their interaction fields with certain probes (CH3 for alkyl, NHamide, and carbonyl, O− of COO−), representing the decisive functional groups of the active site, have been calculated using GRID and projected into the enzyme placing the structures according to the position of A-98881 in the enzyme- inhibitor complex. The strongest calculated fields of the O− probe were found near Asp 25 for both structures. Another respective conformity consists in the overlap of the fields for the NHamide probe near Ile 50 and 50′ for the investigated cage dimer and A-98881.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008038608460
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