Stereoselective synthesis of a topologically chiral molecule: the trefoil knot.

Topological chirality of a molecule is realized when any representation of its graph is topologically distinct from its mirror image, i.e. if it can not be converted to its mirror image by continuous deformation in 3D-space. [1] This property implies that the graph of the molecule is non-planar. Molecular systems with an intrinsically non-planar graph are scare. Their graphs can be contracted to Kuratowski's graphs K5 (the complete graph on five vertices) or K3,3 (the complete bi-partite graph on two sets of three vertices each). [2-4] Many examples of such systems are known, the 3-rung Möbius strip prepared by Walba et al. more than 20 years ago being a particularly representative example. [5]