Please use this identifier to cite or link to this item: http://hdl.handle.net/10316/12966
Title: 5β,6β-Epoxy-17-oxoandrostan-3β-yl acetate and 5β,6β-epoxy-20-oxopregnan-3β-yl acetate
Authors: Pinto, Rui M. A. 
Salvador, Jorge A. R. 
Paixão, José A. 
Issue Date: 19-Apr-2008
Publisher: International Union of Crystallography
Citation: Acta Crystallographica Section C. 64:5 (2008) o279-o282
Serial title, monograph or event: Acta Crystallographica Section C
Issue: 64
Abstract: In the title compounds, C21H30O4, (I), and C23H34O4, (II), respectively, which are valuable intermediates in the synthesis of important steroid derivatives, rings A and B are cis-(5β,10β)-fused. The two molecules have similar conformations of rings A, B and C. The presence of the 5β,6β-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
URI: http://hdl.handle.net/10316/12966
ISSN: 0108-2701
Rights: openAccess
Appears in Collections:FFUC- Artigos em Revistas Internacionais
FCTUC Física - Artigos em Revistas Internacionais

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