title: Crystal chemistry of some synthetic 2-oxa-steroids: conformation, packing motifs and isostructurality.
abstract: The crystal structures of six synthetic 2-oxa-steroids (A-ring lactone steroids) have been determined by single-crystal X-ray diffraction. The conformation and hydrogen bonding in these oxa-steroids is compared with packing motifs in the natural steroids and the anabolic agent, Anavar. O-H...O hydrogen bonding with lactone carbonyl O is the preferred arrangement in molecules with a C-OH group. The donor H atoms of A, B and D rings participate in C-H...O interactions with lactone carbonyl O and D-ring hydroxyl/ketone O acceptor atoms. The conformation of the lactone ring in these analogues is different from the natural androgens because replacement of the C2-methylene group by an O atom changes the geometry of the A ring. Two structurally related lactone steroids provide the first example of O-H...O/C-H...O interaction mimicry and furthermore the two components form a binary solid solution. The O-H...O and C-H...O hydrogen bonds in 2-oxa-steroid crystal structures are analysed and the observed preferences discussed in terms of geometric and chemical factors.
authors.affiliation: School of Chemistry, University of Hyderabad, India.
authors.forename: A
authors.initials: A
authors.lastname: Anthony
authors.forename: M
authors.initials: M
authors.lastname: Jaskólski
authors.forename: A
authors.initials: A
authors.lastname: Nangia
mesh_terms: D018360:Crystallography, X-Ray; D008968:Molecular Conformation; D013256:Steroids / Q000737:chemistry*
chemical_list: D013256:Steroids