2006 Volume 22 Pages x89-x90
5 β,6 β-Epoxy-4 β,27-dihydroxy-1-oxo-22R-witha-2,24-dienolide (C28H38O6) was isolated from the leaves of Withania somnifera. The structure of the withanolide was established by spectral analysis and X-ray diffraction studies as withaferin A. The compound crystallizes in the orthorhombic space group P212121 with unit-cell parameters: a = 10.697(1), b = 12.344(2), c = 18.714(2)Å, Z = 4. The crystal structure was solved by direct methods and refined to R = 0.0382 for 2471 observed reflections. The ring conformations are: A twist-boat, B half-chair, C chair, D envelope, E distorted sofa. The twist along the length of the steroid nucleus is negligible [C19-C10…C13-C18 = 1.9°]. Both hydroxy groups are involved in hydrogen bonding.
