Chiral discrimination of 2-arylalkanoic acids by (1S,2R)-1-aminoindan-2-ol through the formation of a consistent columnar supramolecular hydrogen-bond network

Abstract

Enantiopure cis-1-aminoindan-2-ol was selected as a basic resolving agent for racemic 2-arylalkanoic acids on the basis that its rigid cis-conformation would favor the formation of a supramolecular hydrogen-bonded column, in which chiral discrimination of the racemic carboxylate would occur. It was found that this amino alcohol possesses high resolving efficiency for a variety of racemic acids; also, X-ray crystallographic analyses of the diastereomeric salts showed that a columnar hydrogen-bond network is formed in both the less- and more-soluble diastereomeric salts, as we had expected. A detailed study on the stabilising interactions suggested that there are two that play an important role: (i) hydrogen bonding between the ammonium and hydroxy groups and the acid carboxylate, which determines the formation of the columnar network and (ii) CH⋯π, which influences the herringbone packing of the aromatic groups, implying that it also plays some role in chiral discrimination.