Crystal and molecular structure of carolenalone, a cycloheptenone sesquiterpene lactone from north carolina Helenium autumnale L

X-Ray single crystal analysis has established the structure and relative stereochemistry of the title compound (I). Crystals are orthorhombic, space group P212121, a = 7.31 (1), b = 21.20(1), c = 9.21 (1) Å, Z = 4. The structure was solved by direct methods and atomic positional and thermal parameters were refined by full-matrix least-squares calculations to R 0.078 over 476 reflections from diffractometer measurements. The cycloheptenone ring adopts a flattened twist-chair conformation in which the C:C·C:O system with a torsion angle of -157° is distinctly non-planar. The cyclopentane and γ-lactone rings are both in envelope conformations; the C(11) methyl group is β-oriented.

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Author Andrew T. McPhail Chemistry