Crystal and molecular structure of an enantiomeric gossypol-acetic acid clathrate

Single crystals of gossypol with three molecules of acetic acid (gossypol t riacetic acid) were grown from solutions of gossypol acetic acid and aceton e. The crystals were unstable in air but could be stabilized for X-ray diff raction analysis by coating the crystal surfaces with a thin layer of miner al oil. The gossypol triacetic acid complex (C30H30O8. 3C(2)H(4)O(2)) forms an orthorhombic crystal system with P2(1)2(1)2(1) (Z = 4) symmetry.. Unit cell dimensions were a = 9.0208(7) Angstrom, b = 17.4884(10) Angstrom, and c = 24.358(2), Angstrom yielding a volume of 3842.7(5) Angstrom(3) and a de nsity of 1.2077(2) g/cm(3). As with all previously reported crystals of gos sypol, the gossypol molecules were of the aldehyde tautomer, and the two pl anar naphthalene rings were approximately perpendicular. Acetic acid molecu les were found to lie in channels within the gossypol matrix. Individual cr ystals contained only one gossypol enantiomer, but both enantiomers crystal lized from solution. Although the crystal habit could not be used to distin guish between the gossypol enantiomers, a fragment of the crystal could be derivatized and analyzed by high-performance liquid chromatography for this purpose. The ability to grow large, nonracemic crystals leads to a simple procedure for separating small quantities of the individual gossypol enanti omers.