STRUCTURES OF 3 INCLUSION-COMPOUNDS OF CHOLANAMIDE WITH EITHER (S)-ENANTIOMER, (R)-ENANTIOMER OR AN OPTICALLY RESOLVED MIXTURE OF BUTAN-2-OL

The three types of inclusion compounds of cholanamide (CAM, 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholan-24-amide) have been crystalliz ed from the solutions of (S)-butan-2-ol (CAMSB), (R)-butan-2-ol (CAMRB ) and racemic butan-2-ol (CAMSRB), respectively. The crystal structure s have been determined. The three crystal structures are isomorphous t o each other and revealed that the host CAM molecules form the same la yered arrangements, providing channel spaces for the guest butan-2-ol molecules. As expected, the CAMSB and CAMRB crystals include the pure (S)- and (R)-enantiomers of butan-2-ol, whereas the (S)-enriched mixtu re of enantiomers is accommodated in CAMSRB with a molar ratio between the host CAM and guest butan-2-ol molecules of 1:1. The hydrogen-bond network is rigidly formed between the CAM molecules and also between CAM and butan-2-ol molecules. CAMSB and CAMRB have slightly different unit-cell dimensions: the channels in CAMRB have a larger section, res ulting in a larger unit-cell volume. In CAMSRB, although both enantiom ers of the guest alcohol are included, the (S)-enantiomer is more abun dant, indicating that the optical resolution occurs during the crystal lization step.