Conformation of the sesquiterpenoid zerumbone: X-ray crystallographic analysis of zerumbone 2,4-dinitrophenylhydrazone

Abstract

The molecular geometry of the title compound, C₁₅H₂₂O, has been determined by X-ray diffraction. The double bonds in the 2,6,9,9-tetra methylcycloundea-2,6,10-trienone ring have trans-stereochemistry. The conformation of the macrocycle differs from that found in several derivatives of humulene, C₁₅H₂₄ and is related to one of the low-energy comformations of cycloundecane. Force-field rig calculations indicate that this zerumbone conformation is of lower energy than the alternative humulene-like conformation. Crystallographic data are a= 12.619(2), b= 7.290(3), c= 23.422(3)Å, β= 98.06(1)°Z= 4, space group P2₁/_c. Diffractometer intensity measurements were made with Cu-K_α radiation and least-squares adjustment of the atomic parameters converged at R 0.046 for 3 222 |F_o| values.