French chemist Henri Kagan and Japanese chemist Kenso Soai have won the Nobel Prize in Chemistry for 2026 for their work showing how chemical reactions can amplify small asymmetries in molecules. The Royal Swedish Academy of Sciences said they have been feted “for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis”.
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Mr. Kagan is a professor emeritus at the former Université Paris-Sud, and Mr. Soai is a professor emeritus at the Tokyo University of Science. They will share the prize equally.
The duo’s work is centered on chiral molecules, which are molecules that can exist in two mirror-image forms, like a left and a right hand. The two versions are called enantiomers. Each enantiomer can interact very differently with other chiral molecules — a property that has had an outsized impact on biology.
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For example, the proteins in our bodies are made mostly of amino acids that have one of the two mirror-image arrangements. The enzymes that speed up chemical reactions in cells and the receptors that look out for chemical signals and trigger responses are also chiral. As a result, the two enantiomers of a chiral drug can interact differently with these molecules and elicit different responses, only of which might be desirable.
This was a challenge for chemists who had to manufacture the correct enantiomer of a drug rather than a mixture of both, which was the norm.
Scientists also puzzled over why so many molecules important for life occur in just one of their two possible handed forms.
In 1986, Mr. Kagan and his team made a landmark discovery. Chemists often use catalysts to speed up certain reactions. The team found that the chiral parts of a catalyst could combine in pairs, and opposite-handed pairs could react differently from same-handed ones. If the opposite-handed pairs reacted poorly, they could remove the minority form from the reaction, leaving the active catalyst more one-handed, and producing a disproportionately one-handed product.
Others were able to use this finding to work back from the products of a reaction to its microscopic mechanism, then accordingly redesign the reaction to produce more desirable products.
Soai et al. picked up from here and, in 1995, showed that a chiral molecule could speed up the formation of more molecules with its own handedness. In the so-called Soai reaction, scientists found that even if 0.00005% more right-handed than left-handed molecules entered a reaction, after just three rounds, 99.75% of the molecules could be right-handed.
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The impact of the laureates’ work has also differed. Scientists today use the findings of Mr. Kagan & co. to optimise reactions to produce specific enantiomers of drugs, agrochemicals, and fragrances.
Mr. Soai’s impact, on the other hand, has been on biochemistry: his work has allowed scientists to keep open the possibility that some small, random imbalance in the concentration of enantiomers billions of years ago became amplified to the overwhelming handedness we see in biological molecules today.
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