A new route to chirality

Chirality is an important property of life, from small molecules to the right-handed helix of our DNA. Accessing a single enantiomer from a racemic mixture is a fundamental goal in synthesis, and yet because of the degenerate nature of enantiomers, an equilibrium favouring one or the other enantiomer is not possible. Here, Thorsten Bach and colleagues report a photochemical deracemisation, which allows the formation of a single enantiomer from a racemic mixture of the same compound. On irradiation with light, a chiral sensitizer undergoes energy transfer to the allene substrate. Because this process is different for the two enantiomers, it selectively converts one enantiomer of the racemate and not the other, giving rise to a single enantiomer.