Helical Aromatic Oligoamide Macrocycle Incorporated with a Ferrocene Unit for Encapsulation and Chirality Signaling of Zwitterionic Proline

A strategy for developing ferrocene-incorporated heteroditopic macrocycles for the recognition of zwitterionic proline is presented. The receptor features a well-defined helical cavity, and diastereomeric conformers result upon encapsulation of d/l-proline as indicated by X-ray crystallography. Incorporation of a ferrocene unit allows efficient chirality signaling, which is clearly manifested by circular dichroism and NMR spectroscopy upon guest binding. This work demonstrates a viable approach for constructing ditopic hydrogen-bonded aromatic oligoamide macrocycles capable of sensing zwitterionic amino acids.