Stereospecific Assembly of Triply Chiral Pseudopeptidic Cages Through Dynamic Dual Chirality Transfer

A stereospecific transmission of chiral information within tripodal pseudopeptidic cages has been observed from dynamic constitutional co-operation of reversible orthogonal processes: imine bond and metal coordination. The chiral centers from the phenylalanine amino acid moieties induce a specific chirality into the formed octahedral Fe(II) complex and into the helical twist of the macrobicycle, as confirmed by NMR, circular dichroism, X-ray diffraction of single crystals, and theoretical calculations. Instead, when a configurationally stable Ru(II) complex is employed, the dynamic imine exchange efficiently selects the corresponding matched-combination of the same chiral elements, leading after reduction to a water-soluble homochiral stable macrobicyclic pseudopeptide Ru(II) complex with appealing chemical and photophysical properties. Overall, our study demonstrates how subtle structural factors from a chiral effector in a reversible dynamic system rule the generation and selection of subsequent chiral elements with high fidelity and complete stereocontrol.