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

The asymmetric unit of the title compound, C(30)H(48)O(2), contains two independent mol­ecules, the main difference between them being that the isopropenyl group is rotated by approximately 180°. In each mol­ecule, the fused six-membered 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⋯O inter­actions link the mol­ecules into chains along [010]. Weak intra­molecular C—H⋯O hydrogen bonds are also observed but the hy­droxy groups are not involved in hydrogen bonds.