Isomerization of a second-generation molecular motor (e.g.7 , Figure 3A) leads to helix inversion of the overcrowded
alkene moiety.21,27 The resulting metastable isomers
are diastereomers of the stable isomers. The metastable isomer
(R ,M )-7-ms is the pseudo-enantiomer of its
corresponding stable isomer (R ,P )-7-st . These two
isomers are called pseudo-enantiomers because they are near-mirror
images, except for the methyl group at the stereogenic center.
Metastable isomer (R ,M )-7-ms is pseudo-identical
to the stable isomer (S ,M )-7-st . The term
pseudo-identical, rather than identical, applies here because the point
chirality at the motor stereogenic center differs between the