X-ray structure of a 1 : 2 complex of hexakis (3-O-acetyl-2,6-di-O-methyl)-alpha-cyclodextrin with butylacetate

Crystal structure of a 1:2 complex of hexakis(3-O-acetyl-2,6-di-O-methyl)-a lpha-cyelodextrin (ADMACD) with butylacetate was determined by the X-ray me thod. The space group of the crystal is P2(1)2(1)2(1) With Z = 4 and D-x =1 .293g cm(-3), and the cell dimensions are a = 11.087(2), b = 23.543(3), and c = 31.739(6) Angstrom. The structure was solved by the direct method and refined to the R-value of 0.123 for all the 4993 observed reflections with I > 0. The ADMACD molecule is in a round shape with the pseudo hexagonal sy mmetry. Methyl and acetyl groups point towards the outside of the molecule. Because of the acetyl groups attached to O3 and methyl groups attached to O6, the intramolecular cavity is ca. 3 Angstrom deeper than the cavity of n ative alpha-CD. One butylacetate molecule is coaxially accommodated with it s acetyl group at the O6 side in the host cavity while the other guest mole cule is located in an intermolecular space between host molecules which are stacked to form a head-to-tail channel-type packing structure along the a axis.