Supramolecular control over Diels–Alder reactivity by encapsulation and competitive displacement

A water-soluble M4L6 coordination cage was used as a supramolecular protecting group in the Diels–Alder reaction between furan and maleimide. Encapsulation of furan in the cage prevents the Diels–Alder reaction, while subsequent addition of a competing guest will initiate the reaction.