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  • 1
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray structure of 6-methyl-3,20-dioxo-4,6-pregnadien-17α-yl acetate is reported. The crystals are monoclinic, space groupP21,Z=4,a=28.955(7),b=6.597(2),c=11.064(3) Å,/gb=90.80(2) °. The two crystallographically independent molecules have very similar overall geometries. The A rings have intermediate sofa-half-chair conformations and are bent relative to the steroid skeleton. The conformation of the 17β-progesterone side chain is stabilized by the 17α-ester substituent; the C(16)-C(17)-C(20)-O(20) torsion angle is −19.4(6) and −20.6(7)°.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of 21-fluoro-4,9(ll)-pregnadiene-3,20-dion-17a-yl acetate has been determined by X-ray diffraction methods;P212121,a=15.827(4),b=16.912(4),c=7.513(2) Å,Z=4;R=0.062, (R w =0.065) for 2028 unique observed reflections. The progesterone side chain has an unusual conformation; the C16-C17-C20-O20 torsion angle is 173.1(4)°. Molecular mechanics calculations suggest that this conformation may be cuased by 17α-acetoxy substituent and the additional double bond between C9 and C11.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in space groupP212121 with lattice constantsa=16.253(3),b=17.107(3), andc=8.486(2) Å. The A ring has 1α,2β-half-chair conformation. The calculated steric energy of a 6α-methyl-17α-ester progesterone molecule is lower by about 4 kJ/mol for the normal A-ring conformation. The progesterone side chain has typical conformation for 17α-ester steroids; the C(16)-C(17)-C(20)-O(20) torsion angle is −24.9(4)°.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 71-75 
    ISSN: 0899-0042
    Keywords: crystal structure ; aldosterone conformation ; correction of assigned configuration ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of dilute alkali at room temperature aldosterone undergoes rearrangement to form 11β,18:18,21-diepoxy-20,21-dihydroxy-4-pregnen-3-one (V). X-Ray crystallographic analysis demonstrates that isomers of both 18R, 20S, 21S and 18R, 20S, 21R configuration are formed rather than the 18R, 20R, 21R isomer postulated on the basis of examination of 1H-NMR spectra. The spectra appears to be consistent with the major component of the mixture. The 20S configuration observed is in agreement with the chirality assigned to the degradation product obtained when the same alkaline solution of aldosterone is subjected to reflux. The crystals of (V) are monoclinic P21, Z = 4 with a = 20.891(2), b = 6.3848(5), c = 16.067(2)Å, β = 122.09°(1) with two molecules in the asymmetric unit. Molecule A has the 20S,21S configuration and the molecules in the second site are a mixture of the 20S, 21S and 20S, 21R configuration in the ratio of 3:2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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