Stereoselective Synthesis of a Topologically Chiral Molecule: The Trefoil Knot

Tying nice neat knots is demonstrated on a molecular level with the stereoselective synthesis of a trefoil knot. The key reaction was the completely stereoselective formation of a double-stranded helical precursor from two pinene–bipyridine threads around two CuI centers (the pinene moieties contain stereogenic centers). The helix was then transformed through several steps into 1; demetallation of the complex 1 yielded the configurationally predetermined free trefoil knot.