Enantioselective Synthesis of Mechanically Axially Chiral Rotaxanes

The chiral mechanical axial stereogenic unit of rotaxanes was only recently recognized, despite equivalent mechanically axially chiral catenanes being discussed in the early 1960s. Here we demonstrate that a single H-bond between the groups that differentiate the faces of the macrocycle and axle appears sufficient to deliver high diastereocontrol (80% de) in the mechanical bond forming step and extend this observation to the first direct enantioselective approach in up to 70% ee.