Crystal structure of a synthetic anabolic agent: stanazolol ethanol solvate, 17β-hydroxy-17α methylandrostano[3,2-c]pyrazole ethanoate

Abstract

The crystal and molecular structure of 17β-hydroxy-17α methylandrostano[3,2-c]pyrazole ethanoate (stanazolol ethanol solvate), C2H30N2O⋅C2H5OH, has been determined by direct methods and refined by full-matrix least squares to a final R of 0.0577 for 4021 observed reflections and 245 parameters using Cu Kα radiation, λ = 1.54178 A. The compound crystallizes in space group P212121 with Z = 4 molecules per unit cell. In the steroid skeleton the ring A adopts a half-chair conformation, being considerably strained, as a consequence of the fused planar pyrazole ring E. Rings B and C however are chairs and ring D has a 13β,14α half-chair conformation. All rings of the steroid skeleton are trans-connected. The OH group of the solvated ethanol molecule is hydrogen bonded to the β-oriented carbonyl substituent O(20) of ring D. The molecules are further held together in the crystal structure by head–tail hydrogen bonding between N(1′)H in the pyrazole ring and O(20), which consequently is an acceptor for the two H-bonds. Overall the molecule lacks any significant curvature with no interplanar dihedral angle greater than 7°. Possible binding modes of stanazolol with the human androgen receptor are discussed.