16alpha,17alpha-Epoxy-20-oxopregn-5-en-3beta-yl acetate.
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].