JOHN N. LOW et al. 2037 References Cobo, J. (1995). PhD thesis, University of Ja6n, Spain. Enraf-Nonius (1992). CAD-4/PC Software. Version 1.1. Enraf- Nonius, Delft, The Netherlands. Gabe, E. J., Le Page, Y., Charland, J.-P., Lee, F. L. & White, P. S. (1989). J. Appl. Cryst. 22, 384-387. Johnson, C. K. (1976). ORTEPII. Report ORNL-5138. Oak Ridge National Laboratory, Tennessee, USA. Low, J. L., Ferguson, G., Godino, M. L., Cobo, J., Lopez, R., Melguizo, M., Nogueras, M. & Sanchez, A. (1996). Acta Cryst. C52, 418-420. Sheldrick, G. M. (1993). SHELXL93. Programfor the Refinement of Crystal Structures. University of Grttingen, Germany. Spek, A. L. (1995a). PLATON. Molecular Geometry Program. Version of July 1995. University of Utrecht, The Netherlands. Spek, A. L. (1995b). PLUTON. Molecular Graphics Program. Version of July 1995. University of Utrecht, The Netherlands. Comment As a part of our study of the Beckmann fragmentation reaction in a series of steroidal tertiary a-hydroxy- imino alcohols, the synthesis of 17a-benzyl-17~-hydro- xy - 16 - hydroxyimi no - 3 - methoxyestra- 1,3,5 (10) - triene, (2), was performed (Miljkovir, Ga~i, Medir-Mijarevir, Stankovi6 & Lazar, 1995). Regioselective addition of benzyllithium to the 17-carbonyl group of 16-hydroxy- imino-3-methoxyestra-1,3,5 (1)-triene- 17-one, (1), afforded the title compound, (2). Its structure, deduced from chemical spectroscopic evidence, was confirmed by X- ray diffraction analysis. /~o . , /OH H H 3 C O - ' ~ OH H3CO (1) (2) Acta Cryst. (1996). C52, 2037-2040 17c~-Benzyl-17/3-hydroxy-16-hydroxyimino- 3-methoxyestra-l,3,5(10)-triene SLOBODANKA STANKOVIC, a DU~AN LAZAR, ~ DU~AN MILJKOVI6, b LJUBICA MEDIC-MIJACEVI6,b KATARINA GA~I, b RADMILA KOVA~VI6 c AND CHRIS]lANE COURSEILLE d alnstitute of Physics, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovida 4, 21000 Novi Sad, Serbia, blnstitute of Chemistry, Faculty of Sciences, University of Novi Sad, Novi Sad, Serbia, Clnstitute of Biology, Faculty of Sciences, University of Novi Sad, Novi Sad, Serbia, and dLaboratoire de Cristallographie et de Physique Cristalline, Facultd des Sciences, Universitd de Bordeaux L Talance, France (Received I May 1995; accepted 28 November 1995) Abstract The asymmetric unit of the title compound, 17c~-benz- yl- 16 - hydroxyimino - 3 - methoxyestra- 1,3,5( 10 ) - trien- 17/3-ol, C26H31NO3, contains two molecules which differ in the orientations of the methoxy groups at C(3). The 17-hydroxy and 16-hydroxyimino moieties are involved in intramolecular N...O and intermolecular N-..O and O...O hydrogen bonds. The hydrogen-bond network accounts for the differences in bond and torsion angles of the a-hydroxyimino moieties of the symmetry- independent molecules. This has been confirmed by molecular-mechanics calculations on the individual mol- ecules which indicate that they have the same geometry in their energy minimum states. @ 1996 International Union of Crystallography Printed in Great Britain - all rights reserved Perspective views of the two symmetry-independent molecules, (I) and (II), of compound (2) are shown in Fig. 1. Selected geometric parameters are given in Ta- ble 2, together with corresponding values (in square brackets) obtained from molecular-mechanics calcula- tions. The puckering (Cremer & Pople, 1975) and asym- metry parameters (Duax, Weeks & Rohrer, 1976) listed in Table 3 reveal usual ring conformations. Ring B has a 7a,8~-half-chair conformation; the distances of atoms C(7) and C(8) from the best plane of the remain- ing four atoms are -0.369(7) and 0.413 (6),~,, respec- tively, for molecule (I), and -0.319 (7) and 0.437 (6)A for molecule (II). Ring C has a chair conformation, while ring D exhibits a conformation between a 13~- envelope [the distance of atom C(13) from the best Molecule (I) c%c, Molecule ClI) Fig. 1. A perspective view of the two symmetry-independent mol- ecules, (I) and (II), of the title compound. Displacement ellipsoids are plotted at the 40% probability level. Acta C~.stallographica Section C ISSN 0108-2701 © 1996