A cyclic trimer of 2-(2-aminophenoxy)propionic acid with a bowl-shaped structure

Abstract

A cyclic trimer of ( R)-2-(2-aminophenoxy)propanoic acid, a δ-amino acid analogue, was synthesized. Molecular mechanics calculations on the cyclic trimer predicted that a concave network of sequential hydrogen bonds forms a C 3-symmetric bowl-shaped structure. Evidence for this conformation was found in the NMR spectra of the trimer in d-chloroform. Although the single-crystal structure of the cyclic trimer indicates that chloroform could be included in the bowl-shaped structure, the conformation was not C 3-symmetric and the hydrogen bonding network was of a different mode. These different conformations between solid and solution were reasonably clear from IR spectra.