Steroidal Wheel-and-Axle Host Type Molecules: Insights from Awkward Shape, Conformation, Z′ > 1 and Packing

The synthesis and crystal structure of three new molecular rotors derived from levonorgestrel and norethisterone are reported. The conformation, close contacts, and shape characteristics of these molecules exhibiting Z′ = 2 and the inclusion of solvent molecules were analyzed together with the crystal structures of parent molecules retrieved from the Cambridge Structural Database. For the set of estranes studied, we confirmed that whenever an alternative conformer cannot satisfy the crystallographic symmetry, a second molecule is incorporated in the asymmetric unit resulting in conformational isomorphism (Z′ > 1). The shape of these molecules could make them interesting as potential hosts.