Lup-20(29)-en-28-ol-3-one (betulone)

The asymmetric unit of the title compound, C30H48O2, contains two independent molecules, the main difference between them being that the isopropenyl group is rotated by approximately 180 degrees. In each molecule, the fused sixmembered rings have chair-chair-chair-chair conformations and the cyclopentane ring adopts an envelope conformation with the C atom bearing the hydroxymethyl group as the flap. All ring junctions are trans-fused. With the exception of one of the methyl groups adjacent to the C O group, all the methyl groups are in axial positions. The isopropenyl group is equatorial and the hydroxymethyl group is in an axial orientation. In the crystal, weak C-H center dot center dot center dot O interactions link the molecules into chains along [ 010]. Weak intramolecular C-H center dot center dot center dot O hydrogen bonds are also observed but the hydroxy groups are not involved in hydrogen bonds.