Divergent Anion Hosts from a Single Macrocyclic Precursor via Anion-Assisted Skeleton Editing or Late-Stage Functionalization

Acid cleavage of Boc-protected amide macrocycles 1 affords ammonium salts 2·HCl that undergo skeleton editing via macrocyclic ring-opening transamidation to give linear analogues 3·HCl. Addition of base suppresses this transformation, preserving the macrocyclic framework for late-stage functionalization. Isomeric pentamide hosts 4 and 5 derived from 2 and 3 display contrasting anion-recognition profiles in polar media: macrocyclic 4a preferentially binds chloride, whereas linear 5a strongly and selectively recognizes dihydrogen phosphate.