CRYSTAL-STRUCTURE OF DRATED-6(A),6(C),6(E)-TRI-O-METHYLCYCLOHEXAAMYLOSE AND ITS CONFORMATION IN SOLUTION

The crystal structure of uncomplexed 6A6C,6E-tri-O-methylcyclohexaamyl ose(dagger) (CD-3OMe) has been determined by X-ray analysis. The struc ture was solved by molecular replacement methods and refined by the fu ll matrix least-squares method to the R-value of 0.074. Cyclodextrin m olecules are arranged in a herring-bone cage-type packing. Inside the cavity only two water molecules are found close to the primary hydroxy l rim. One O-methyl group of a molecule is inserted into a neighbourin g host molecule from the secondary hydroxy side. The conformation of C D-3OMe was also studied in solution by NMR spectroscopy. In particular heteronuclear 3J(C-13-H-1) coupling constants through the glycosidic linkages were measured. The results obtained in deuteriated water and pyridine could be intepreted in terms of an averaged flexible conforma tion.