(1R,3S,8R)-3,7,7,10-Tetra-methyl-tri-cyclo-[6.4.0.0(1,3)]dodec-9-en-11-one.

The absolute configuration of the title compound, C16H24O, has been deduced from the chemical pathway. The six-membered ring has a roughly half-chair conformation with the quaternary C atom as the flap. The seven-membered ring displays a chair conformation. In the crystal, there is a weak C-H⋯O hydrogen bond between the methyl-ene group of the cyclo-propane ring and the carbonyl group of a screw-axis-related mol-ecule, which builds up a zigzag-like chain along the b-axis direction.