Supramolecular Catalysis of the oxa-Pictet-Spengler Reaction with an Endohedrally Functionalized Self-Assembled Cage Complex

An endohedrally functionalized self-assembled Fe(4)L(6)cage complex can catalyze oxa-Pictet-Spengler cyclizations of tryptophols and various aldehyde derivatives, showing strong rate accelerations and size-selectivity. Selective molecular recognition of substrates controls the reactivity, and the cage is capable of binding and activating multiple different species along the multistep reaction pathway. The combination of a functionalized active site, size-selective reactivity, and multistep activation, all from a single host molecule, illustrates the biomimetic nature of the catalysis.