Chiral discrimination of 2-arylalkanoic acids by (1S,2S)-1-aminoindan-2-ol and (1S,2S)-2-aminoindan-1-ol:: Correlation of the relative configuration of the amino and hydroxy groups with the pattern of a supramolecular hydrogen-bond network in the less-soluble diastereomeric salt

The diastereomeric resolution of 2-arylalkanoic acids with enantiopure trans-1-aminoindan-2-ol and trans-2-aminoindan-1-ol were studied. Enantiopure trans-1-aminoindan-2-ol had a moderate resolving ability for 2-arylalkanoic acids having a naphthyl group as an aryl substituent at the alpha-position, while enantiopure trans-2-aminoindan-1-ol had a moderate-to-high resolving ability for a wide variety of the acids having a methyl group as an alkyl substituent at the alpha-position. The crystal structures of the corresponding less-soluble salts revealed that a reinforced columnar hydrogen-bond network was formed in the less-soluble salts with trans-1-aminoindan-2-ol, while a rather stable hydrogen-bond sheet was generated with the assistance of water molecules in the less-soluble salts with trans-2-aminoindan-1-ol. These results suggest that not only the relative configuration but also the position of the hydrogen-bonding groups in resolving agents have a considerable effect on the structure of the less-soluble salts. The difference in favorable hydrogen-bond structure determined the adaptivity to the structural feature of target racemic 2-arylalkanoic acids in the resolution by trans-1-aminoindan-2-ol and trans-1-aminoindan-2-ol, respectively.