Completely stereospecific synthesis of a molecular cinquefoil (51) knot

Although several molecular prime knots have been prepared to date, their stereoselective synthesis is still a rare occurrence. Here, we report a two-step, completely stereospecific preparation of a molecular cinquefoil (51) knot in 86% yield. The knotted product is generated from the covalent capture of a pentameric circular helicate. The absolute configuration of amino acid ester within the ligand strand directly determines the helical chirality of the circular helicate, the handedness, and the topological writhe of the knot. An open helicate features layered packing in the solid state, providing a scaffold for molecularly woven polymers. Several anions bind weakly to the well-organized central cavity of the knot through hydrogen bonding. Topological chirality alone induces all-important changes in the environment around the chromophores. Transfer of chirality in knot synthesis opens up opportunities for the assembly of other chiral nanotopologies and exploring the consequences of topological stereochemistry in chemistry, materials, and biology.