Crystal structure of 3,4a, 7,7,10a-pentamethyl-3-vinyldodecahydro-1H-benzo[f]chromen-9-ol isolated from Sideritis perfoliata

The asymmetric unit of the title compound, C20H34O2, contains two crystallographically independent molecules (1 and 2) with similar conformations. In both molecules, the cyclohexane rings adopt a chair conformation, while the oxane rings are also puckered. In the crystal, O-H center dot center dot center dot O hydrogen bonds connect adjacent molecules, forming C(6) helical chains located around a 21 screw axis and running along the crystallographic a axis. The packing of these chains is governed only by van der Waals interactions. Semi-empirical PM3 quantum chemical calculations are in a satisfactory agreement with the structural results of the X-ray structure analysis. The absolute structure was indeterminate in the present experiment.