A Cyclochiral Conformational Motif Constructed Using a Robust Hydrogen-Bonding Network

A novel conformational motif constructed with a robust intramolecular hydrogen-bonding (H-bonding) network was discovered. A pyrrolidine derivative possessing four identical amide substituents at C(2) and C(5) formed a strong intramolecular H-bonding network consisting of all the amide groups. This conformation yielded a cyclochiral structure with a handedness that depended on the directionality of the H-bonding network. The most stable compound was isolated and applied to the acylative kinetic resolution of secondary alcohol. The handedness of the H-bonding network was biased by the presence of chiral substituents, and the preferred direction could be switched under an external stimulus. A structural analysis using NMR, X-ray crystallography, and theoretical calculation techniques indicated that the conformation of the substituents was highly ordered and depended on the directionality of the H-bonding network.