trans- and cis-3-Aminoindan-1-ols were prepared by moderately selective reductions of 3-aminoindan-1-one derivatives and separated into enantiopure forms. The enantiopure trans-isomer had a moderate resolving ability for 2-arylalkanoic acids having a naphthalene ring at the α-position. The X-ray crystallographic analysis showed that an infinite hydrogen-bond sheet was formed in the less-soluble salt, suggesting that the skeleton of these indanols would be favorable for the stabilization of the less-soluble salt by hydrogen-bonding interaction.

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 ␣-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 ␣-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. Chirality 15: 564-570, 2003. © 2003 KEY WORDS: optical resolution; diastereomeric salt; crystal engineering; amino alcohol; 2-arylalkanoic acid Clarification of the chiral discrimination mechanism upon crystallization of diastereomeric co-crystal is a fascinating subject, which will have great influence in a wide variety of research fields such as molecular recognition, crystal engineering, and so on. 1 In particular, extraction of the characteristics of the crystal structures of diastereomeric crystals is of great importance, since it would afford valuable information for designing a resolving agent for a given target racemate.We recently found that the chiral discrimination of 2-arylalkanoic acids by enantiopure cis-1-aminoindan-2-ol (1) occurred through the formation of a consistent columnar hydrogen-bond network.2 In the crystals of the less-soluble diastereomeric salts, the hydroxy group of 1, locating in a cis-configuration with the amino group, afforded further intracolumnar hydrogen bonds with the ammonium hydrogens and carboxylate oxygens, which contributed to the formation of a columnar hydrogen-bond network, to increase the stabilization of the less-soluble salts. The formation of such a stable reinforced columnar hydrogen-bond network would enhance the differentiation in stability between the less-and more-soluble diastereomeric salts to lead the high-resolution ability of 1 for 2-arylalkanoic acids. On the other hand, in the course of our continuous studies on the design of acidic resolving agents, we have found that the formation of a supramolecular hydrogen-bond sheet in the less-soluble salt is an essentially important factor for the successful resolution of 1-arylalkylamines with enantiopure arylglycolic acids. 3,4 Comparing the two hydrogen-bond structures w...

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