STEREOCHEMISTRY OF VALERENANE SESQUITERPENOIDS - CRYSTAL-STRUCTURE OF VALERENOLIC ACID

The three-dimensional structure of valerenolic acid, C15H22O3), was determined by x-ray crystallography. The substance crystallizes in the orthorhombic space group P212121 and the unit-cell dimensions are a=12.705 (2), b=14.476 (3), c=15.477 (1) Å. Intensity data were measured with Cu radiation on a four-circle diffractometer. The structure was solved by direct methods and refined to R=3.6% for 2543 reflections. The hydroxyl group attached to the five-membered ring is cis to the hydrogen atom at the adjacent ring junction, and both are trans to the axial methyl substituent on the six-membered ring. The latter is trans to the methacrylic acid side chain, in which the methyl group is cis to the ring carbon atom. Chemical and spectroscopic data indicate that the same stereochemistry also occurs in valerenic acid and in valerenal. The absolute configuration was established on the basis of the CD spectrum of methyl 1-ketovalerenate. © 1978, American Chemical Society. All rights reserved.