K. Bhattacharyya et al., Crystal and molecular structure and absolute configuration of WithaperuvinE: a C-28 steroidal lactone, J CHEM CRYS, 28(7), 1998, pp. 571-575
The withanolide Withaperuvin E, C28H36O8, has been obtained from the air dr
ied roots of Physalis peruviana and purified by silica gel chromatography.
This compound exhibits significant antineo plastic activity. Prismatic pale
yellow crystals were obtained from a methanol/acetone solution. The compou
nd crystallizes together with a partially occupied [40(1)%] acetic acid mol
ecule, in space group P2(1)2(1)2(1), Z = 4, D-c = 1.242 g cm(-3), with unit
, cell parameters a = 11.431(3), b = 14.104(1), c = 17.387(5) Angstrom, V =
2803.2(11)Angstrom(3), and mu(CuK alpha) = 0.072mm(-1). Through the X-ray
analysis the molecule was found to be comprised of a steroidal skeleton wit
h a beta-oriented oxygen bridging atoms C(5) and C(6) in ring B. Steroid ri
ng conformations are: A sofa; B sofa; C chair; D intermediate half-chair/so
fa; the lactone ring E has a sofa conformation. All rings of the steroid sk
eleton are trans connected. The absolute configuration of the Withaperuvin
E skeleton corresponds to that of naturally occurring steroids, C(18) and C
(19) both being beta-oriented. The partially occupied acetic acid molecule
forms a hydrogen bond to the steroid molecule. Hydrogen bonding also occurs
between OH(14) and a symmetry related oxygen O(20) of the steroid.