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The Crystal and Molecular Structure of Dianhydrogossypol
Dianhydrogossypol (4,4'-dihydroxy-5,5'-diisopropyl-7,7'-dimethyl-bis(3H-naphtho[1,8-bc]furan-3-one)) was made by refluxing gossypol in m-xylene. Proton NMR spectroscopy was used to confirm that complete conversion was achieved over a time period of several hours. Single crystals of the compound were obtained by slow evaporation from dichloromethane. Diffraction studies indicate that this crystal form is tetragonal with a I4₁/a space group and with cell dimensions of a = b = 33.8265(4) Å, c = 9.1497(2) Å, V = 10469.4(3) Å³ at 100 K. The structure was solved by direct methods and was refined to an R1 value of 0.0415 on 6,408 independent reflections. Dianhydrogossypol exists as a pair of enantiomers within this structure. The two fused planar ring systems are oriented at a 117° angle to each other (i.e., close to perpendicular), and the isopropyl groups are oriented with the ternary carbon hydrogen atoms pointed inward toward the center of the molecule. Repeating groups of four molecules (of the same chirality) pack to form a helical structure that is supported by intermolecular hydrogen bonds. Each helix is surrounded by four neighboring helices that are composed of molecules of the opposite chirality. The helices form the walls of empty channels that are 5-6 Å wide. As has been found for some gossypol crystal forms, the open-channel structure of dianhydrogossypol might be useful for scavenging or carrying small molecules. Additional NMR studies confirm that dianhydrogossypol can be converted directly to gossypol lactol ethers in the presence of anhydrous alcohols.
Talipov, Samat A.
Mamadrakhimov, Azimjon A.
Tiljakov, Zavkibek G.
Dowd, Michael K.
Ibragimov, Bakhtiyar T.
Xonkeldieva, Muhabbat T.
chemical constituents of plants
Journal of the American Oil Chemists' Society 2009 Mar., v. 86, no. 3
Berlin/Heidelberg : Springer-Verlag
Journal Articles, USDA Authors, Peer-Reviewed
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
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