Diosgenin hemihydrate

Diosgenin [or (22R,25R)-spirost-5-en-3β-ol] is the starting material of the Marker degradation, a cheap semi-synthesis of progesterone, which has been designated as an Inter­national Historic Chemical Landmark. Thus far, a single X-ray structure for diosgenin is known, namely its dimethyl sulfoxide solvate [Zhang et al. (2005 ▶). Acta Cryst. E61, o2324–o2325]. We have now determined the structure of the hemihydrate, C(27)H(42)O(3)·0.5H(2)O. The asymmetric unit contains two diosgenin mol­ecules, with quite similar conformations, and one water mol­ecule. Hy­droxy groups in steroids and water mol­ecules form O—H⋯O hydrogen-bonded R (5) (4)(10) ring motifs. Fused edge-sharing R(10) rings form a backbone oriented along [100], which aggregates the diosgenin mol­ecules in the crystal structure.