In 2002, Puddephat and co-workers reported a chiral catenane composed of two achiral rings with distinct faces (Cnv) (Fig. ) . A small number of axially chiral catenanes as a racemic mixture have been reported 9 , but no enantiopure examples where the mechanical bond provides the sole source of stereochemistry have been disclosed to date . Furthermore, unlike the example of topologically chiral catenanes, the notional process of ring opening and stoppering of the minimal representation of such mechanically axially chiral catenanes does not result in a chiral rotaxane (Fig. ). To address this challenge, we re-examined the mechanical axial stereogenic unit of catenanes with a focus on not just the symmetry of the components but how this arises structurally (Supplementary section 12). This led us not only to an efficient approach to enantiopure mechanically axially chiral catenanes but also to recognize and synthesize a noncanonical class of mechanically chiral rotaxanes that had previously been overlooked.