On 7 October 2026, the Royal Swedish Academy of Sciences awarded the Nobel Prize in Chemistry to two pioneers of asymmetric synthesis: making one mirror-image form of a molecule rather than both. The prize of 12 million Swedish kronor is shared equally.
The laureates
- Henri B. Kagan, born 1930 in Boulogne-Billancourt, France. Professor Emeritus at the then Université Paris-Sud, France.
- Kenso Soai, born 1950 in Hiroshima, Japan. Professor Emeritus at Tokyo University of Science, Japan.
The prize was awarded “for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis”.
The puzzle: life is one-handed
Many molecules are chiral: they exist as two mirror-image forms, called enantiomers, like a left and a right hand. Living things use only one form. The amino acids in your proteins are all the same “hand”, and so is the sugar in your DNA: one form, never both. Chemists call this homochirality.
Yet when chemists ran reactions that make chiral molecules, they always obtained an equal mixture of the two forms. So how could one hand ever win? The question matters for medicines too: often only one enantiomer of a drug has the wanted effect, while the other can cause harmful side effects, as the thalidomide tragedy of the early 1960s showed.
A recipe on paper
In 1953 the physicist Charles Frank described three conditions that could lead to homochirality:
- a chiral catalyst that drives an asymmetric reaction (more of one enantiomer than the other);
- a way of boosting one enantiomer and holding back the other;
- autocatalysis: the product is itself the catalyst, so the favoured enantiomer makes more copies of itself.
The first condition had already been met (asymmetric catalysis was recognised with the Nobel Prizes of 2001 and 2021). The 2026 prize rewards the other two.
Kagan: the non-linear effect (1986)
Catalysts for asymmetric reactions often combine a metal atom with a chiral molecule. Chemists assumed that the purity of the product simply follows the purity of the catalyst: a straight-line (linear) relationship.
Kagan questioned this. He reasoned that each metal atom holds at least two of the chiral molecules, so a catalyst made from a mixture of enantiomers contains three forms: left–left, right–right and left–right. The mixed left–right form turned out to work much more slowly than the other two. As a result, the product contained a greater excess of one enantiomer than the catalyst did. When he plotted his results, the graph was curved: a non-linear effect.
Soai: a molecule that copies its own handedness (1995 and 2003)
Soai searched for a chiral molecule that could catalyse its own formation. He found one, a 5-pyrimidyl alkanol. In 1995 he reported a reaction that began with a 2 % excess of one enantiomer and ended with an 87 % excess: the reaction reinforced itself.
In 2003 he went further. Starting from molecules that were not chiral, chance produced a tiny excess of one enantiomer, which then took over the reaction: up to 99.99 % of the product could be one form. Repeating the experiment, sometimes the other enantiomer won. This was the first time anyone, other than life itself, had created this kind of one-handedness from scratch.
Why it matters
- Non-linear effects are now an everyday tool for chemists who design reactions to make pure enantiomers of pharmaceuticals, flavours, scents and agricultural chemicals.
- The Soai reaction shows how homochirality can arise on its own, and has inspired research into how life’s one-handed molecules first appeared.
Written by Chemistry Clarity from the official information on NobelPrize.org; see the links below for the full story and illustrations.