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  • 1980-1984  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Steroids and related studies. Part LIV. The crystal and molecular structure of 17aβ-(2-hydroxyethyl)-3β-pyrrolidino-17a-aza-d-homo-5-androstene dimethiodide (hs-626) (1982)
    Springer
    Journal of chemical crystallography 12 (1982), S. 255-270 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of the potent synthetic aza steroidal neuromuscular blocking agent 17aβ-(2-hydroxyethyl)-3β-pyrrolidino-17a-aza-D-homo-5-androstene dimethiodide (HS-626), (C27H48N2O)2+2I−, has been determined by the heavy-atom method and refined by block diagonal least squares toR o =0.044 for 3041 observed reflections andR=0.072 for 4313 reflections measured on a four-circle diffractometer in the ω/2θ scanning mode, employing Nb-filtered MoKα radiation. The crystals are orthorhombic,P212121,a=14.671(2),b=17.594(3),c=10.908(2) Å,Z=4. RingsA, C, andD-homo have chair conformations, ringB is a half-chair, and the pyrrolidine ringE has an envelope conformation. The N+---N+ distance of 10.33 Å is within the usual range associated with potent neuromuscular blocking. The hydroxyethyl side group appended to N+ (17a) forms part of an acetylcholine-like moiety which is observed to adopt thet,-g conformation commonly found in acetylcholine. This feature probably accounts for the dramatic increase in potency of HS-626 compared to similar drugs lacking this feature. Potential-energy calculations for the free HS-626 molecule indicate that the side chain may adopt a variety of conformations in the ranget, (+ g to− g).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01195717
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  • 2
    Electronic Resource
    Electronic Resource
    Crystal and molecular structures of two polymorphs of 4-methyl-2-nitroacetanilide (MNA) (1983)
    Springer
    Journal of chemical crystallography 13 (1983), S. 279-292 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of white (MNA-1) and yellow (MNA-3) forms of 4-methyl-2-nitroacetanilide have been determined by X-ray diffraction techniques. The crystals of MNA-1 are monoclinic,a=10.421(2),b=9.980(2),c=9.568(2) Å,β=99.51(2)°, space groupP21/c,Z=4. Crystals of MNA-3 are triclinic,a=17.956(2),b=12.908(2),c=4.039(1) Å,α=93.13(2)°,β=83.71(2)°, γ=90.77(2)°, space groupP¯1,Z=4. Both structures were solved by direct methods using theShelx-76 system of programs, and refined using full-matrix least squares. The number of unique reflections used in refinement and the finalR values are: MNA-1, 1545, 0.067; MNA-3, 3127, 0.065. The two distinct molecules in MNA-3 have intramolecular hydrogen bonds and different molecular conformations, although both are fairly planar, and each type is closely packed in columns of parallel molecules along thec direction. In MNA-1 the C=O⋯H-N geometry is indicative of intermolecular hydrogen bonding and the molecules adopt a conformation in which the nitro and amide groups lie in planes at approximately 45° to the benzene ring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01158908
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  • 3
    Electronic Resource
    Electronic Resource
    The role of X-ray crystallography in drug design: Identification of the two isomers 17β-hydroxy-17α-methyl-5(β andα)-androstano-(2,3-C)-1′, 2′, 5′-oxadiazole (HS804 and HS805) (steroids and related studies, Part 62) (1984)
    Springer
    Journal of chemical crystallography 14 (1984), S. 315-332 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystal structure analysis has distinguished between the two epimers 17β-hydroxy-17α-methyl-5(β andα)-androstano-(2, 3-C)-1′, 2′, 5′-oxadiazole (HS804 and HS805). HS804 is trigonal,P32,a=14.820(4),c=7.177(3) Å,Z=3 and HS805 is orthorhombic,P212121,a=9.507(4),b=18.528,c=10.048(4) Å,Z=4. The crystal structures were solved by direct methods and refined by full-matrix least squares toR=0.0376 for 1419 reflections (HS804) andR=for 1819 reflections (HS805), using diffractometer measured data with CuKα radiation. The two molecules have different ring connections,A/B cis in HS804 andA/B trans in HS805, the planar oxadiazole ring beingcis fused to ringA in both molecules. RingA is strained in both molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01168550
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  • 4
    Electronic Resource
    Electronic Resource
    The refined structure of ribonuclease-A at 1.45 Å resolution (1984)
    Springer
    Journal of chemical crystallography 14 (1984), S. 467-494 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Features of the refined X-ray crystal structure of bovine pancreatic ribonuclease-A at 1.45 Å resolution are described. The positions of the protein atoms have been determined within the range 0.004–0.05 Å, and of solvent atoms, assumed to be oxygens, within the range 0.08–0.13 Å. The present model contains 127 solvent molecules, taken to be water, and a sulfate anion located in the active site. Mean square atomic displacement parameters,U iso, refined for each atom, give an indication of the mobility of different parts of the structure. Main-chainU iso values tend to be less than side-chain values, having an average value of 0.15 Å2 compared to 0.25 Å2. Both main-chain and side-chain averageU iso values tend to increase with distance from the center of gravity of the molecule. Side-chain averageU iso values also tend to increase with the number of atoms in the side-chain, with different distributions for ring and chain type residues. Side-chain conformations have been analyzed and found on the whole to follow commonly observed distributions. A notable exception to this is the active-site residue His-119 which occupies two distinct sites. Apart from two small clusters of eight and seven atoms respectively, the solvent molecules are distributed in quite small numbers on the protein surface. The solvent clusters occur in the active-site region and, together with the sulfate anion, appear to stabilize residues in this region. Sixty-three solvent atoms have only one identified hydrogen bond contact. Of the rest, 36 form two, 22 form three, and 6 form four hydrogen bonds. There is a marked tendency for the mean square displacement parameter,U iso, for the solvent atoms to be lower for atoms with many hydrogen bond contacts than for those with fewer contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160695
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  • 5
    Electronic Resource
    Electronic Resource
    Steroids and related studies, Part LIII. Structure and function of synthetic bisquaternary aza steroidal neuromuscular blocking agents (1980)
    Springer
    Journal of chemical crystallography 10 (1980), S. 31-53 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The molecular structures of three dimethiodide bisquaternary aza steroids, determined crystallographically, are reported. The compounds are (i) 17a-methyl-3β-pyrrolidino-17a-aza-d-homo-5-androstene dimethiodide (HS310, or chandonium iodide), (ii) 4,17a-dimethyl-4, 17a-diaza-d-homo-5α-androstane dimethiodide (HS342), and (iii) 4-methyl-17β-dimethylamino-4-aza-5α-androstane dimethiodide (HS467). RingB in HS310 is a half-chair and ringD in HS467 is a distorted envelope. All other rings in the steroid skeletons of the three molecules are in the chair conformation, and all rings aretrans-connected. All three molecules are known to exhibit competitive neuromuscular blocking activity, each with different potency. This is discussed in relation to the observed inter-onium N+ ⋯ N+ distances and other features of molecular geometry of importance in drug design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01209551
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  • 6
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of stercuronium iodide ethanol solvate: A peripheral muscle relaxant (1981)
    Springer
    Journal of chemical crystallography 11 (1981), S. 87-103 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of the muscle relaxant stercuronium iodide in the form of its ethanol solvate C26H43N2 +I− · C2H5OH, has been determined by the heavy-atom method and refined by block-diagonal least-squares toR o = 0.062 for 1941 observed reflections andR = 0.079 for a total of 2420 reflections measured on a four-circle diffractometer in the ω/2θ scanning mode. The crystals are monoclinic,P21,a = 15.386(5),b = 11.377(4),c = 8.307(3) Å, β = 98.22(2) °,Z = 2. RingsA andB in the modified conessine skeleton are both highly symmetrical half-chairs, ringC is in the chair conformation, and ringsD andE are highly symmetrical envelopes. The pyrrolidine ringE fused to ringD is roughly perpendicular to the steroid skeleton formed by ringsA toD. The N+---N distance of 10.76 Å is within the usual range required for potent neuromuscular blocking. Semiquantitative results are presented which suggest that the site of the tertiary N atom in ringE is not heavily congested by neighboring atoms in the molecule and may therefore be susceptible to protonation under physiological conditions. This could account for the relatively high drug potency of stercuronium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200883
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  • 7
    Electronic Resource
    Electronic Resource
    Steroids and related studies. Part 60. Crystal and molecular structures of 17β-(2-hydroxyethyl)-3β-and 3α-pyrrolidino-17a-aza-D-homo-5-androstenes: HS-625 form 1, (3β-pyrrolidino) and HS-625 form 2 (mixed-3α and -3β-pyrrolidino epimers) (1984)
    Springer
    Journal of chemical crystallography 14 (1984), S. 89-115 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of two forms of 17β-(2-hydroxyethyl)-3-pyrrolidino-17a-aza-D-homo-5-androstene (HS-625) are reported. In HS-625 (aqueous solvate) form 1, moleculeA, and HS-625 (anhydride) form 2, moleculeB, the pyrrolidine group is 3-β substituted, while in HS-625 (anhydride) form 2, moleculeC has its pyrrolidine ring α-substituted. HS-625 form 1 is orthorhombic, space groupP212121, witha=7.089(4),b=11.502(6),c=28.975(16) Å,Z=4; form 2 is triclinic, space groupP1, witha=14.013(8),b=12.572(6),c=6.688(4) Å, α=95.187(20), β=103.491(21); γ=86.210(20)°,Z=2. MoleculesA andB have similar geometry, differences in moleculeC being related to strain caused by the unusual 3-α ring substituent which also produces a pronounced kink in the backbone of the molecule. An unusual feature of the analysis of form 1 is the location of the water hydrogens in the difference electron density well above background. None of the OH hydrogens was located. Both structures are hydrogen bonded, but the pyrrolidine nitrogen N(31) in moleculeC is heavily congested and is unable to act as an acceptor. The hydroxyethyl side chain, important for activity, has a different conformation in the three molecules (t,g, t,-g, andt,t respectively).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01161425
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  • 8
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of an amber polymorph of 4-methyl-2-nitroacetanilide (MNA) (1984)
    Springer
    Journal of chemical crystallography 14 (1984), S. 283-291 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a third polymorph of 4-methyl-2-nitroacetanilide has been determined by X-ray diffraction. It crystallizes in the monoclinic system, space groupP21/c,Z=4,a=10.158(2),b=11.635(2),c=8.041(2) Å andβ=94.55(2)°. Using 1027 unique reflections, the structure was solved by the method of vector verification and refined by full-matrix least squares, which gave convergence toR=0.080. The structure consists of nearly planar molecules, all approximately parallel to one another with their longitudinal axes parallel tob. The amide group forms an intramolecular hydrogen bond with the nitro group. Molecules related byc-glide are stacked alongc in a very distinct columnar form. The columns are held together by dipole-dipole interactions between close antiparallel carbonyl groups or between close antiparallel nitro groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01161165
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular structure of an ancient folk medicine: Berberine hydrogen sulfate (1984)
    Springer
    Journal of chemical crystallography 14 (1984), S. 269-281 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of the versatile folk medicine berberine hydrogen sulfate, (C20H18NO4)+HSO 4 − , has been determined by the heavy-atom method and refined by blocked full-matrix least-squares refinement. The crystals are triclinic, space groupF¯1,a=20.370(5),b=7.435(2),c=27.427(6) Å,α=97.700(9),β=116.222(9),γ=85.456.(8)°,Z=8,D x =1.556 g cm−3,D m =1.549(5) g cm−3. The structure refined toR=0.070 for 1659 observed reflections withI(hkl)≧2.5σ[I(hkl)]. The ring system of the berberine molecule is approximately planar, with both −OCH3 groups twisted slightly out of the plane. Heterocyclic ringB has a half-chair conformation with a pseudo-two-fold axis bisecting the bonds C(9)-C(10) and C(7)-C(8), diagonal to the isoquinoline groupAB. The five-membered ringE has an envelope conformation, the apical atom C(1) being out of plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01161164
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