(1S,3R,8R)-9-(1-Amino­ethyl­idene)-2,2-dichloro-3,7,7-trimethyl­tricyclo­[6.4.0.0(1,3)]undecan-10-one

The title compound, C(16)H(23)Cl(2)NO, was synthesised from β-himachalene (3,5,5,9-tetra­methyl-2,4a,5,6,7,8-hexa­hydro-1H-benzocyclo­heptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The mol­ecule contains a seven membered ring, which is fused to a five- and a three-membered ring. The five-membered ring has a twisted conformation, whereas the seven-membered ring displays a chair conformation. The dihedral angle between the five- and seven-membered rings is 45.26 (9)°. The absolute structure was established unambiguously from anomalous dispersion effects. In the crystal, mol­ecules are linked into chains propagating along the b axis by inter­molecular N—H⋯O hydrogen bonds; an intramolecular N—H⋯O link also occurs.