5Beta,6beta-epoxy-17-oxoandrostan-3beta-yl acetate and 5beta,6beta-epoxy-20-oxopregnan-3beta-yl acetate.
ABSTRACT In the title compounds, C(21)H(30)O(4), (I), and C(23)H(34)O(4), (II), respectively, which are valuable intermediates in the synthesis of important steroid derivatives, rings A and B are cis-(5beta,10beta)-fused. The two molecules have similar conformations of rings A, B and C. The presence of the 5beta,6beta-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.
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ABSTRACT: A structural and conformational study of 3β-acetoxy-17-chloro-16-formyl-5α-androstan-16-ene has been carried out by using X-ray analysis and M06-2X density functional calculations. The compound crystallizes with three independent molecules in the asymmetric unit. Natural Bond Order and Atoms in Molecules methods were used for a better understanding of the key factors that determine the stability of this steroidal molecule, particularly the role of C–H⋯Cl intramolecular interactions. A detailed investigation of C–H⋯Cl and C–H⋯O intermolecular interactions, in addition to the most important van der Waals contribution, are presented by means of Hirshfeld surface analysis. The crystal packing exhibits an unusual intra- and intermolecular hydrogen bond pattern, and shows the importance of non-classical interactions in the construction of the supramolecular assembly. Excellent agreement between the theoretical and experimental data is found.CrystEngComm 06/2014; 16:7802-7814. · 3.86 Impact Factor
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ABSTRACT: The title steroid, C23H33NO8, is a pregnane derivative obtained regio-, stereo- and chemoselectively from the ring opening of the corresponding 5α,6α;16α,17α-diepoxide with bismuth(III) nitrate. There are two symmetry-independent molecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. All rings are trans-fused. The conformations of the six-membered rings are close to chair forms, while the five-membered ring adopts an envelope conformation. The molecules are held together by an extensive O—H⋯O hydrogen-bonding network of chains runnning along the a axis.Acta Crystallographica Section E Structure Reports Online 05/2009; 65(6). · 0.35 Impact Factor
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ABSTRACT: The title steroid, C31H53NO4, was prepared from the corresponding 5α,6α-epoxycholestane. The conformation of the six-membered rings is close to a chair form, while the five-membered ring adopts a twist conformation. The hydroxyl and acetamide groups are in axial positions. The nucleophilic species bound to the steroid nucleus at position 6 by the β-face, whereas the hydroxyl group at position 5 has α-orientation. All rings are trans-fused. The crystal packing shows that the molecules related by twofold symmetry exist as O—H⋯O hydrogen-bonded dimers.Acta Crystallographica Section E Structure Reports Online 11/2008; 64(12). · 0.35 Impact Factor