Crystallographic Studies of Cyclodextrin Inclusion Complexes and Neat Guest Molecules .Jennifer M. Alexander, Joanna L. Clark, Tom J. Brett, Charles R. Ross II, and John J. Stezowski, Department of Chemistry, University Of Nebraska-Lincoln, Lincoln, NE 68588-0304.

Single crystal X-ray diffraction methods are being used to study several (-cyclodextrin ((-CD) inclusion complexes of derivatized D- and L-amino acids. The guest molecules have been crystallized in the absence of (-CD to compare their conformations to those observed in the inclusion complex. Data sets have been collected for several guests and structures have been determined for N-acetyl-L-phenylalanine methyl and ethyl esters, N-acetyl-D-phenylalanine, N-acetyl-L-tyrosine methyl ester, and N-acetyl-L-tryptophan. N-acetyl-L-phenylalanine ethyl ester crystallizes in space group P2₁, the remainder in P2₁2₁2₁. Crystallization of the host-guest complex for each of the above guests with (-CD is underway.

X-ray measurements will be compared with solid-state nmr data to describe the host-guest interaction. The neat guest structures described above will be compared to the included guest. By studying the differences in these structures, we hope to increase our understanding of the interactions involved in molecular and chiral recognition.