organic papers o1224 G. Vasuki et al. C 29 H 37 NO 4 H 2 O DOI: 10.1107/S1600536802017932 Acta Cryst. (2002). E58, o1224–o1226 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 3b ,17b -Diacetoxy-16-(3-pyridylmethylene)- androst-5-ene monohydrate G. Vasuki, a V. Parthasarathi, a * K. Ramamurthi, a S. Dubey b and D. P. Jindal b ² a Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, India, and b University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh 160 014, India ² Deceased. Correspondence e-mail: sarati@yahoo.com Key indicators Single-crystal X-ray study T = 293 K Mean (C–C) = 0.007 A ˚ H-atom completeness 95% Disorder in main residue R factor = 0.062 wR factor = 0.181 Data-to-parameter ratio = 8.8 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. # 2002 International Union of Crystallography Printed in Great Britain – all rights reserved In the title compound, C 29 H 37 NO 4 H 2 O, an androst-5-ene steroid, rings A and C adopt chair conformations, while ring B is in a half-chair conformation. The five-membered ring D adopts an envelope conformation. The molecular packing is probably stabilized by intermolecular O—HN and O— HO hydrogen bonds involving the disordered water molecules. Comment The X-ray investigation of the title compound, (I), was undertaken as part of our study on the structure and confor- mation of new synthetic steroid derivatives (Hema et al., 2002; Vasuki et al., 2001; Vasuki, Parthasarathi, Ramamurthi, Dubey & Jindal, 2002a,b; Vasuki, Parthasarathi, Ramamurthi, Jindal & Dubey, 2002a,b; Vasuki, Thamotharan, Parthasarathi, Ramamurthi, Jindal & Dubey, 2002; Vasuki, Thamotharan, Parthasarathi, Ramamurthi, Dubey & Jindal, 2002). We are particularly interested in the study of the possible influence of various substituents at the C3, C16 and C17 positions (Fig. 1) on the conformation of the steroid nucleus, as it is well known that steroid receptors are able to modify the mode of binding at ring D to accommodate several different types of C17 substitution (Duax & Norton, 1975). In (I), rings A and C adopt chair conformations. The C5— C6 (Csp 2 —Csp 2 ) distance of 1.306 (6) A ˚ confirms the locali- zation of a double bond at this position. As a result of this double bond, the geometry around atom C5 is planar and hence ring B adopts an 8,9-half-chair conformation, with Q = 0.503 (5) A ˚ , = 50.1 (6) and ’ = 210.0 (7) (Cremer & Pople, 1975). Similar observations have been reported for related structures (Hema et al., 2002; Vasuki et al., 2001; Vasuki, Parthasarathi, Ramamurthi, Dubey & Jindal, 2002a; Vasuki, Thamotharan, Parthasarathi, Ramamurthi, Jindal & Dubey, 2002). Ring D has a 13-envelope conformation, with Cs (C13) = 2.9 (5) and the pseudo-rotational parameters = 41.6 and ’ m = 47.3 (3) (Altona et al., 1968). The B/C and C/D ring junctions show trans fusion. The usual chair conformation adopted by ring A is not disturbed by the Received 2 September 2002 Accepted 30 September 2002 Online 18 October 2002