A cystine-bearing pseudo-cyclopeptide as a new amphi-receptor

A conformationally constrained cyclic peptide was designed and synthesized as a novel amphi-receptor. It binds to cations or anions through the carbonyl or amino groups, respectively. The stability of the cation complexes relies largely on the polarizability of the cation, whereas the stability of the anion complexes relies on the strength of the H-bond as well as the polarizability of the anion.