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  • 21
    Electronic Resource
    Electronic Resource
    Crystal structure of 17-oxo-5α-androstano [3,4-C] 1′2′5′-oxadiazole (HS1000) (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 725-729 
    Details
    ISSN: 1572-8854
    Keywords: Synthetic steroids ; progesterone analogs ; antifertility profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound (C19H26N2O2) is one of a series of novel heteroatom steroidal derivatives recently prepared for testing their antifertility profiles and progesterone binding affinity. It is one of a pair of epimers differing in configuration at position 5. The X-ray analysis has uniquivocally resolved this ambiguity. The compound crystallizes in space group P212121, a = 9.257(3), b = 9.419(3), c = 19.089(5)Å, and Z = 4 and the structure was solved by direct methods. In the steroid skeleton Ring A does not exhibit the chair conformation commonly found in the steroid nucleus, being considerably strained, presumably as a consequence of the fused planar oxadiazole ring E. Rings B and C, however, are chairs and ring D is in an intermediate envelope/half-chair conformation. All rings of the steroid skeleton are trans connected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021856309954
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  • 22
    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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  • 23
    Electronic Resource
    Electronic Resource
    Steroids and related studies, part 75: The crystal and molecular structure of 17a-(2-hydroxyethyl)-17a-aza-D-homo-5-androsten-3βol (HS407) (1989)
    Springer
    Journal of chemical crystallography 19 (1989), S. 483-498 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of 17a-(2 hydroxyethyl)-17a-aza-D-homo-5-androsten-3βol, C22 NO2 H33 (HS407), an intermediate in the formation of azasteroidal neuromuscular blocking agents, has been determined by Vector Verification and refined by full-matrix least-squares toR=0.058 for 1805 reflections, Cu Kα radiation,θ≦65.49°. The space group is P21212,a=25.537(5),b=9.847(4),c=7.545(5) Å,Z=4. The rings in the modified steroid nucleus are alltrans connected, with A and C in distorted chair conformations, D a symmetrical chair, and B a half-chair. The hydroxyethyl side-chain in position N (17a) adopts two distinct conformations with approximately equal statistical occupancies: the first, having a coiled conformation, forms a close intramolecular contact with N(17a) in the enlarged ring D of the steroid nucleus, while the alternative side chain position, which is extended, participates in tail-to-tail intermolecular hydrogen bonding. A switch mechanism is thus formed which could influence the mode of binding of this type of drug moleculein vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185385
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  • 24
    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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  • 25
    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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  • 26
    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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  • 27
    Electronic Resource
    Electronic Resource
    Structure of tetrazole steroid analogues, IV: Structure of 7a-aza-B-homocholest-5-eno [7a, 7-d]tetrazol-3β-yl-acetate (HS503) (1987)
    Springer
    Journal of chemical crystallography 17 (1987), S. 51-69 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the steroidal tetrazole 7a-aza-B-homocholest-5-eno[7a,7-d]tetrazol-3β-yl acetate (C29H46N4O2) has been determined by vector verification, and refined to a finalR of 0.087 for 3454 observed reflections. The compound crystallizes in space groupP21 with cell dimensionsa=7.352(3),b=25.950(8),c=15.408(6) Å,β=91.22(3)°;Z=4,D x=1.33 g cm−3, μ(CuKα)=4.87 cm−1. The two independent molecules exhibit similar overall topography, ringsA, B, C, andD adopting chair, butterfly (Husainet al., 1981), sofa, and distorted envelope conformations respectively in both molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01181959
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  • 28
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of benzoyl-l-leucyl-glycine ethyl ester (l-LEUGLY) (1987)
    Springer
    Journal of chemical crystallography 17 (1987), S. 783-797 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of the dipeptide derivative benzoyl-l-leucylglycine ethyl ester has been determined by direct methods (Multan 78), and refined by fullmatrix least squares toR=0.092 for 1638 reflections;I〉3σ(I), CuKα radiation. The space group isP212121,a=20.679(7),b=16.440(6),c=11.034(5) Å,Z=8. Disorder observed in the ethyl ester and leucyl side-chains of the two independent molecules per asymmetric unit probably accounts, at least partially, for the weak diffracting power of the crystals. Both molecules exhibit markedly coiled hydrogen-bonded conformations. An attempt was made to obtain improved hydrogen bond geometry by the use of neutron diffraction data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160742
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  • 29
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of 4,17a-methy1-4, 17a-diaza-5α-androstane (HS353): An intermediate in the design of azasteroid neuromuscular blocking agents (1989)
    Springer
    Journal of chemical crystallography 19 (1989), S. 237-256 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of 4, 17a-methyl-4, 17a-diaza-5α-androstane (HS353), C20N2H36 has been determined by direct methods and successive electron density calculations. The crystals are triclinic,a=7.419(2),b=20.300(4),c=12.866(2)Å,α=105.91(2),β=76.33(2),γ=99.32(2)°, space groupP1,Z=4. Block-matrix least-squares refinement converged toR=0.0660 for 3243 reflections withI≧3σI (CuKα radiation). The four independent molecules show only minor conformational variations, all rings being trans-connected chairs. Introduction of N at positions 4 and 17a of ringsA andD creates asymmetry in both conformation and bond angles, producing outward bending of the C-N side groups at both ends of all four molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01194120
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  • 30
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of 5-carbamyl-5H-dibenzo[b,f] azepine (1989)
    Springer
    Journal of chemical crystallography 19 (1989), S. 641-649 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of the title compound has been determined by direct methods from diffractometer data, and refined by full-matrix least squares. Crystals are monoclinicP21/n,a=7.534(1),b=11.150(2),c=13.917(3) Å,β=92.94(4)°,Z=4,D x=1.34 (3) g cm−3,R=0.084 for 1259 observed reflections. The azepine ring has a boat conformation. The fused benzene rings are planar. Molecules are packed as hydrogen-bonded dimers through the carboxamide groups. The atomic charge distribution over the fused ring system is approximately symmetrical.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01179836
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