Acta Cryst. (2008). C64, o279-o282 [ doi:10.1107/S0108270108009621 ]
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,6-Epoxy-17-oxoandrostan-3-yl acetate and 5,6-epoxy-20-oxopregnan-3-yl acetateAbstract: In the title compounds, C21H30O4, (I),10)-fused. The two molecules have similar conformations of rings A, B and C. The presence of the 5,6-epoxide group induces a significant twist of the steroid nucleus and a strong flattening of the B ring. The different C17 substituents result in different conformations for ring D. Cohesion of the molecular packing is achieved in both compounds only by weak intermolecular interactions. The geometries of the molecules in the crystalline environment are compared with those of the free molecules as given by ab initio Roothan Hartree-Fock calculations. We show in this work that quantum mechanical ab initio methods reproduce well the details of the conformation of these molecules, including a large twist of the steroid nucleus. The calculated twist values are comparable, but are larger than the observed values, indicating a possible small effect of the crystal packing on the twist angles.
Formula: C21H30O4 and C23H34O4
 |   Structure factor file (CIF format) (128.2 kbytes) |
| Structure factor file (CIF format) (144.4 kbytes) |
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