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  • 1990-1994  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of 0,0,0-propan-1,2,3-trithionobenzoate (3TBZ): Implication for thermally induced solid-state transformation of 3TBZ (1991)
    Springer
    Journal of chemical crystallography 21 (1991), S. 511-518 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of 0,0,0-propan-1,2,3-trithiobenzoate (3TBZ) has been determined by direct methods. Crystals are monoclinic,a=6.810(2),b=35.950(2),c=9.415(2) Å,β=94.78(2)°, space group P21/c,Z=4. The structure was refined using full-matrix least-squares toR=0.078,R w=0.064, 1957 reflections CuK α radiation, λ=1.5418 Å. The molecule has one relatively short S---C (methylene) intramolecular distance, S(2)---C(38)=3.440(4)Å, approximately 1.5 Å less than the shortest S---C distance observed in related crystal structures. An hypothesis related to this short contact is proposed in order to account for the unusual pyrolitic behavior of this compound in the solid state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160668
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Symmetry old and new: Some recent examples of the role of symmetry in X-ray analysis (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 51-60 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Two recent examples in X-ray structure analysis at opposite ends of the molecular weight range, in which very careful consideration of space group and diffraction symmetry was necessary to resolve all the associated problems, are described. Case 1 involves the structures of (1) transdiBromo (1,4,8,11-tetraazacyclotetradecane) chromium (III) bromide and (2) the corresponding trans-bromo-chloro compound. Both crystallise in space groupP42/m with unit cell dimensions sufficiently close to suggest that the structures are isomorphous. It is shown however that the structures are not superimposable or even related by simple rotation or inversion, but that it is necessary to apply a hypothetical glide operation in order to bring the structures into coincidence. The organic moieties are thus structural enantiomorphs in spite of existing in a centrosymmetric space group. Case 2 involves studies on a co-crystallised derivative of the enzyme RNase with deoxycytidylyl-3′–5′-deoxyguanosine (dCpdG). Preliminary X-ray precession photographs, from low quality crystals, indicated an orthogonal C-centred unit cell, but were unable to define the true diffraction symmetry, which wasnot orthorhombic. The true symmetry was discovered only after solving the structure in a second (erroneous) cell and careful inspection of the lattice and diffraction symmetry from the measured intensity values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665345
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal and molecular structures of O,O-propan-1,3-dithionobenzoate (2TBZ-A), O,O-2,2-dimethylpropan-1,3-dithionobenzoate (2TBZ-B), and O,O,O,O-pentaerythritoltetrathionobenzoate (4TBZ) (1991)
    Springer
    Journal of chemical crystallography 21 (1991), S. 601-614 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structures of three thionobenzoates have been determined: O,O-propan-1,3-dithionobenzoate (2TBZ-A) is tetragonal witha=13.086(2),c=19.048(2) Å, space groupI41/a,Z=8; O,O-2,2-dimethylpropan-1,3-dithionobenzoate (2TBZ-B) is monoclinic witha=13.851(5),b=12.428(3),c=10.996(4) Å,β=104.01(4)°, space groupP21/c,Z=4; and O,O,O,O-pentaerythritol-tetrathionobenzoate (4TBZ) is triclinic witha=15.423(4),b=10.924(3),c=10.698(2) Å,α=112.43(2),β=100.64(2), γ=104.57(2)°,Z=2, space groupP¯1. The structures were all solved by direct methods and refined by least squares toR=0.046 for 886 reflections (2TBZ-A),R=0.075 for 1458 reflections (2TBZ-B) andR=0.075 for 2975 reflections (4TBZ),I〉3σ(I) in each case, CuKα radiation, λ=1.5418 Å. The minimum S---CH2 intramolecular distances in these three structures are significantly larger than the minimum corresponding distance in O,O,O-propan-1,2,3-trithionobenzoate (3TBZ) (Moore and Palmer, 1990), thus providing a possible explanation of why 2TBZ-A, 2TBZ-B, and 4-TBZ are inert with respect to pyrolitic solid-state isomerization; whereas 3TBZ readily undergoes thermally induced rearrangement (Das, 1978; Hedgley, 1981).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01161083
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  • 4
    Electronic Resource
    Electronic Resource
    Crystal structure and charge distribution for 20 oximino-5α-pregn-16-eno[3, 4,-c]-1′2′5′-oxadiazole (HS998) (1993)
    Springer
    Journal of chemical crystallography 23 (1993), S. 273-278 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of the modified steroid, 20 oximino-5α pregn-eno [3, 4-c] 1′2′5′ oxadiazole (HS998) using X-ray diffraction is reported. HS998 crystallizes in the orthorhombic space groupP212121, having cell parametersa=13.465(3),b=18.792(4),c=7.598(2) Å;Z=4. The structure was solved by direct methods and refined by full matrix least squares toR=0.060 for 3478 reflections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01263586
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Polymorphism in Dethoxyprone, a steroidal anesthetic. II. Crystal and molecular structure of 11α-dimethylamino-2β-ethoxy-3α-hydroxy-5α-pregnan-20-one (Dethoxyprone, form II) (1993)
    Springer
    Journal of chemical crystallography 23 (1993), S. 279-283 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of 11α-dimethylamino-2β-ethoxy-3α-hydroxy-5α-pregnan-20-one (Dethoxyprone, formII) (C25H43NO3) has been determined by direct methods, and refined to a finalR of 0.067 for 4508 observed reflections. The compound crystallizes in space groupP212121 with cell dimensionsa=10.830 (2),b=12.703 (2),c=17.490 (1) Å;Z=4,D x =1.12 g cm−3,μ (CuK α)=5.28 cm−1. The rings of the steroid skeleton are trans connected. Rings A, B, and C have chair conformations, while ring D has a half-chair conformation. The molecules are hydrogen bonded in a head to tail fashion through the hydroxy and keto groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01263587
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  • 6
    Electronic Resource
    Electronic Resource
    Structure, absolute configuration, and conformation of a fused complex cyclic carbohydrate from a cameroon plant extract (CAMT2) (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 775-781 
    Details
    ISSN: 1572-8854
    Keywords: Folk Medicine ; Limonoid ; Antimalarial ; Immunomodulator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the natural product C29H38O9, an extract from a Cameroonian plant, has been determined by direct methods. Crystals are orthorhombic, P212121,a=24.571(4),b=16.398(3),c=13.778(4) Å,Z-8,D c=1.270 mg/m3. The final R-factor for 2892 reflections withI〉2σ(I) is 0.0531. The two molecules forming the asymmetric unit have very similar molecular geometry. each molecule comprising a nucleus of six fused rings B to G: where B=pyranyl, C=pyranyl, D=furanyl, E=cyclohexene, F=pyranyl, G=cyclohexyl. Ring B also has a furanyl side-group (ring A). The ring conformations in both molecules are: A (1/2-chair/envelope); B(envelope); C(envelope); D(1/2-chair); E(1/2-chair); F(envelope); G(chair). In the cyclohexene ring E the substitution pattern is 2-hydroxy 3-methyl 5-dimethyl. The two molecules in the asymmetric unit are linked by two OH...O hydrogen bonds to form the crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01668240
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