Crystal Structure of 3-Oxo-4-Aza-5-Alpha-Androstone-17 β-Tert-Butyl Carboxamide with an O···H–(C, N) Acceptor Four-Center Hydrogen Bond

Abstract

The title compound, C23H38N2O2, is the saturated form of a modified steroid derivative Finasteride, containing a δ-lactamide ring, fused to successive cyclohexane and cyclopentane rings which contain a tert-butylamide residue. It crystallizes in the monoclinic space group C2 with unit cell parameters a = 9.99450(10), b = 7.67870(10), c = 28.4954(3), Å, β = 93.8706(10)°, Z = 4. Crystal packing effects are influenced by intermolecular hydrogen bond interactions dominated by an acceptor O···H–(C, N) four-center hydrogen bond interaction around the keto oxygen atom from the δ-lactamide ring in the asymmetric unit. Intramolecular three-center C–H···O hydrogen bonds around the tert-butylamide oxygen atom appear to have little effect on crystal packing. A comparison of the geometric parameters of the asymmetric unit (a 5α isomer) is made and with a solvated analog compound (a 5β isomer) and some solvated Finasteride compounds which differ only in the unsaturation of the C1=C2 bond in the δ-lactamide ring. The dihedral angle between the mean planes of the fused δ-lactamide and cyclohexane rings is 2.5(8)° which differs significantly from the 74.8(8) and 76.1(9)° values observed in the solvated analog compound and with its geometry optimized (MOPAC) computed structure, respectively. Crystal structure of 3-oxo-4-aza-5-alpha-androstone-17 β-tert-butyl carboxamide with an O···H–(C, N) acceptor four-center hydrogen bond around the keto oxygen atom from the δ-lactamide ring in the asymmetric unit is reported and its geometric and packing parameters described and compared to related solvent and analog compounds and to a MOPAC computational calculation of the geometry optimized molecule.