Macrocycle 2, which contains a prochiral sulfoxide, was readily synthesized (Supplementary section 3) using a Ni-mediated macrocyclization protocol . Catenane formation (Supplementary section 4) was achieved by reacting (R)-1 with macrocycle 2 under active template Cu-mediated alkyne-azide cycloaddition (AT-CuAAC) conditions to give separable diastereomers 3 in which co-conformational motion is prevented by the bulky ester and N-Boc groups (route a). Catenanes 3 could also be accessed by reaction of (R)-1 with macrocycle 4 to give (Rco-c)-5 followed oxidation to give catenanes 3 (route b). Routes a and b proceeded with appreciable but opposite stereoselectivity. Single crystal xray diffraction (SCXRD) analysis of the major product of rac-1 and 2 allowed the different major stereoisomers produced in routes a and b to be assigned (Fig. , Supplementary section 11.1).