Ca2+-induced folding of a chiral ditopic receptor based on a Pybox ligand and enhancement of anion recognition

A chiral Pybox ligand bearing two urea units was developed for a Ca2+-induced folding ligand. 1 : 1 Ca2+ complexation of the Pybox ligand afforded chiral foldamer formation with coordination of the urea carbonyls to Ca2+. The halide-ion affinity of the foldamer was enhanced compared to Ca2+-free Pybox ligands.