6beta-Hydroxy-5beta-methyl-20-oxo-19-norpregn-9(10)-en-3beta-yl acetate.

In the title compound, C(23)H(34)O(4), which is an intermediate in the synthesis of pregnane derivatives with a modified skeleton that show potent abortion-inducing activity, the conformation of ring B is close to half-chair due to the presence of both the C=C double bond and the axial 5beta-methyl group. Rings A and C have conformations close to chair, while ring D has a twisted conformation around the bridgehead C-C bond. Molecules are hydrogen bonded via the hydroxyl and acetoxy groups into infinite chains. Quantum-mechanical ab initio Roothan Hartree-Fock calculations show that crystal packing might be responsible for the low values of the angles between rings A and B, and between ring A and rings C and D, as well as for a different steric position of the methyl ketone side chain compared to the geometry of the free molecule.