X-Ray crystal-structure analysis of detigloylswietenine p-iodobenzoate has determined the constitution and absolute stereochemistry of the tetranortriterpenoid swietenine, a constituent of Swietenia macrophylla. The crystals of the p-iodobenzoate are orthorhombic, space group P212121, with four molecules of C34H37O9I in a unit cell of dimensions a= 17·44, b= 16·36, c= 11·20 Å. Initial phase determination was based on the iodine atom and Fourier and least-squares methods were employed for the refinement of the atomic parameters. The final value of the discrepancy R over the 1533 independent observed reflexions is 9·8%.
