title: 16alpha,17alpha-Epoxy-20-oxopregn-5-en-3beta-yl acetate.
abstract: The title compound, C23H32O4, has a 3beta configuration, with the epoxy O atom at 16alpha,17alpha. Rings A and C have slightly distorted chair conformations. Because of the presence of the C5=C6 double bond, ring B assumes an 8beta,9alpha-half-chair conformation slightly distorted towards an 8beta-sofa. Ring D has a conformation close to a 14alpha-envelope. The acetoxy and acetyl substituents are twisted with respect to the average molecular plane of the steroid. The conformation of the molecule is compared with that given by a quantum chemistry calculation using the RHF-AM1 (RHF = Roothaan Hartree-Fock) Hamiltonian model. Cohesion of the crystal can be attributed to van der Waals interactions and weak intermolecular C-H.O interactions, which link the molecules head-to-tail along [101].
authors.affiliation: Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, Portugal.
authors.forename: L C
authors.initials: LC
authors.lastname: Andrade
authors.forename: J A
authors.initials: JA
authors.lastname: Paixão
authors.forename: M J
authors.initials: MJ
authors.lastname: de Almeida
authors.forename: R M
authors.initials: RM
authors.lastname: Martins
authors.forename: H I
authors.initials: HI
authors.lastname: Soares
authors.forename: G J
authors.initials: GJ
authors.lastname: Morais
authors.forename: M J
authors.initials: MJ
authors.lastname: Moreno
authors.forename: M L
authors.initials: ML
authors.lastname: Sá e Melo
authors.forename: A S
authors.initials: AS
authors.lastname: Campos Neves
mesh_terms: D018360:Crystallography, X-Ray; D015394:Molecular Structure; D011278:Pregnanes / Q000737:chemistry*; D011284:Pregnenolone / Q000031:analogs & derivatives / Q000737:chemistry*
chemical_list: C431292:16,17-epoxy-20-oxopregn-5-en-3-yl acetate; D011278:Pregnanes; D011284:Pregnenolone