Light - driven deracemization enabled by excited - state electron transfer

Charging through the looking glass Asymmetric catalysis is a commonly applied technique to prepare just one of two mirror-image products in a chemical reaction. But what if you already have the compound you want, stuck in a mixture of left- and right-handed enantiomers? Shin et al. now show that light-induced electron transfer can trigger a favorable succession of proton and hydrogen-atom transfer steps, both of which are susceptible to biasing by catalysts, to preferentially convert a mixture of cyclic urea enantiomers into just one (see the Perspective by Wendlandt). Science , this issue p. 364 ; see also p. 304