Crystal Structue and Absolute Configuration of a New cis-Fused Caryophyllene Derivative. Naematlin 3-p-Bromobenzoate

The molecular structure of naematolin 3-p-bromobenzoate has been determined by X-ray diffraction analysis. Unlike known caryophyllene derivatives isolated so far, the stereochemistry of the ring juncture is cis (1S,9S) form. The absolute configurations of five chiral centers of this compound are 1S,2S,3R,6R, and 9S, and the geometry of endocyclic double bond is E mode. This is the first example of a cis-fused 1S,9S-caryophyllane sesquiterpenoids confirmed by X-ray structure determination. Crystal data and the final R factor are: Mr=491.36, orthorhombic, space group P212121, a=10.650(2), b=20.650(6), c=10.526(2) Å, U=2315(1) Å3, Z=4, Dc=1.410 Mg m−3, μ=1.791 mm−1, R=0.084 for 1666 observed unique reflections.