Early in the development of the chemistry of the mechanical bond, Schill recognized that when a macrocycle containing a prochiral center such that its faces are distinguishable encircles an axle with distinguishable ends, the rotaxane can exist as distinct geometric isomers even though the individual components are stereochemically trivial. Although molecules that correspond to the type 1 3 mechanical geometric isomers (MGI-1) of rotaxanes have been reported, the vast majority where the mechanical bond provides the sole stereogenic unit are constructed from calixarenes or similar macrocycles 7 whose facial dissymmetry arises from the fixed cone-shaped conformation of the threaded ring. In these cases, facial dissymmetry is expressed over the whole macrocycle, which has been shown to lead to stereoselective formation of the corresponding rotaxanes. However, to our knowledge, the only MGI-1 rotaxanes in which a single covalent prochiral center differentiates the faces of the ring, 9 as envisaged by Schill, were reported by Bode and Saito, 10 where no stereoselectivity was reported.