Enantioselective inclusion of chiral alkyl aryl sulfoxides in a supramolecular helical channel consisting of an enantiopure 1,2-amino alcohol and an achiral carboxylic acid

The enantioselective clathrate formation of alkyl aryl sulfoxides 4 was achieved with dissymmetric one-dimensional helical channels created in two-component hosts consisting of (1R,2S)-2-amino-1,2-diphenylethanol 1 and an achiral carboxylic acid, p-tert-butylbenzoic acid 2, or 2-anthraquinonecarboxylic acid 3. X-ray crystallographic analyses showed that the host framework (1R,2S)-1·3 in the single crystal of a clathrate with methyl p-methylphenyl sulfoxide 4n [(1R,2S)-1·3·4n (single)] maintained a supramolecular helical array as those of the solvent-included single crystals (1R,2S)-1·3·EtOH(single) and (1R,2S)-1·3·H2O·THF(single), while the guest 4n molecules were highly disordered. Moreover, the X-ray powder diffraction pattern of (1R,2S)-1·3·4n(clathrate) obtained through the clathrate formation demonstrated that the molecular arrangements of (1R,2S)-1, 3, and 4n were not the same as those which appeared in (1R,2S)-1·3·4n(single); the channel was enlarged. These results are consistently explained by assuming the dynamic motion of the framework (1R,2S)-1·3 to achieve widely applicable clathrate formation.

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