9alpha-Fluoro-16alpha-methyl-3,11-dioxoandrosta-1,4-diene-17beta-carboxylic acid: catemeric hydrogen bonding and acetic acid solvation in a steroidal keto acid related to dexamethasone.
The title keto acid crystallizes as a solvate, C(21)H(25)FO(4).C(2)H(4)O(2), with two molecules each of steroid and acetic acid per asymmetric unit. The former are approximately parallel, with opposite end-to-end orientation, and form translational carboxyl-to-ketone hydrogen-bonding catemers [O...O = 2.679 (6) and 2.650 (5) A, and O-H...O = 165 and 162 degrees] that involve the 3-ketone group and follow the a axis. The acetic acid molecules are paired by hydrogen bonding, and neither they nor the F atom nor the 11-ketone group play any overt role in the hydrogen-bonding scheme of the steroid. Intermolecular C-H...O=C close contacts involving three different neighboring molecules exist to the 11-ketone group, the steroidal carboxyl group and one of the acetic acid molecules.
Carl A. Olson Memorial Laboratories, Department of Chemistry, Rutgers University, Newark, NJ 07102, USA. rogerlal@andromeda.rutgers.edu
Roger A
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Lalancette
Hugh W
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Thompson