Crystal structure of rac-(3aR,4S,5aR,6S,9R,10aS,10bR)-3a,5a,9-tri-methyl-tetra-deca-hydro-6,9-ep-oxy-cyclo-hepta-[e]inden-4-ol monohydrate.

The title hydrate, C17H28O2·H2O, was synthesized in order to determine the relative configuration of the tetra-cyclic framework. The fused 5,6,7-tricarbocyclic core exhibits an entire cis-annulation, featuring a 1,4-cis-relation of the angular methyl groups in the six-membered ring. The oxa bridge of the ep-oxy-cyclo-heptane moiety is oriented towards the concave face of the boat-shaped mol-ecule, whereas the angular methyl groups are directed towards the convex face. The asymmetric unit of the crystal contains two nearly identical formula units, which are related via a pseudo-centre of symmetry. The structure could be solved in the space groups I-4 and I41/a. The refinement in the acentric space group, however, gave significantly better results and these are used in this paper. O-H⋯O hydrogen bonds are observed between the organic mol-ecules, between the organic mol-ecules and the water mol-ecules, and between the water mol-ecules, forming a chain along the c-axis direction.