French chemist Henri B. Kagan and Japanese chemist Kenso Soai have jointly won the 2026 Nobel Prize in Chemistry for discovering nonlinear effects and autocatalysis in asymmetric organic synthesis.

Their research answered a core puzzle that had baffled the chemistry world for more than a century: why life chooses only one mirror image of a molecule.

The Royal Swedish Academy of Sciences said the two laureates' discoveries enabled chemists to drive reactions toward a single chirality, breaking the previous deadlock in which laboratories always produced equal amounts of mirror-image molecules.

Heiner Linke, chairman of the Nobel Committee for Chemistry, commented that the two "provided an answer to a century-old chemistry riddle, and the chemical reactions they developed are breathtaking."

The two will share the 12 million Swedish krona prize.

The honor has direct real-world significance for the pharmaceutical, fragrance and agrochemical industries.

Any company involved in producing substances that interact with living organisms relies on the theoretical framework established by the two laureates — the nonlinear effect discovered by Kagan has become a core tool for optimizing asymmetric synthesis and improving enantiomeric purity, while the autocatalytic reaction system built by Soai achieved, for the first time in artificial chemistry, a complete transformation from achiral to homochiral.

A century-old puzzle: why life has only "one hand"

The chemical composition of living organisms is known as "homochiral" — amino acids exist in two mirror-image forms, but proteins in cells contain only one of them; the sugar molecules that make up DNA are the same.

Yet when chemists tried to synthesize chiral molecules in the laboratory, the two mirror images always appeared in equal proportions and were difficult to separate.

Take the thalidomide scandal of the 1960s: the sedative caused birth defects in thousands of babies, and subsequent research found that it was the mirror-image isomer of the drug's active molecule that caused the harm.

How to obtain only the therapeutically effective mirror image during synthesis became a core issue in pharmaceutical chemistry.

On the theoretical level, British physicist Charles Frank established a mathematical model as early as 1953, pointing out that if a reaction simultaneously satisfies three conditions — chiral catalysis, nonlinear amplification and autocatalysis — homochirality can emerge spontaneously.

But turning this model into chemical reality remained an unresolved case for decades afterward.

Kagan: the nonlinear effect overturns the linear assumption

In 1986, Henri B. Kagan, then at Université Paris-Sud in France, took a key step.

At the time, researchers generally believed there was a linear relationship between catalyst chirality and product chirality — that is, the more chiral catalyst put in, the higher the proportion of the corresponding mirror-image molecule in the product.

Kagan questioned this assumption.

Analyzing the catalyst's structure in depth, he argued that the metal atom in the reaction could simultaneously attract multiple chiral molecules, forming three catalyst forms: "right-right," "left-right" and "left-left."

The key point was that the "left-right" mixed catalyst was far less catalytically efficient than the other two, meaning that when a small amount of the enantiomer was mixed into the catalyst, its interference with the product's chiral ratio was far smaller than expected, so the reaction's asymmetry was amplified.

Experimental results confirmed this inference: the relationship between the chiral ratio in the catalyst and the chiral ratio in the product was a curve rather than a straight line — the so-called "nonlinear effect."

In a paper published that year, Kagan described three asymmetric reactions exhibiting this effect, satisfying the second condition of Frank's model and quickly drawing widespread attention in the chemistry community.

This discovery not only had theoretical value but also gave chemists a practical tool: by judging whether a reaction has nonlinear characteristics, key information about the catalytic mechanism can be obtained, allowing synthesis conditions to be optimized to obtain the target enantiomeric product with higher purity.

Soai: the first complete transformation from achiral to homochiral

Inspired by Kagan's discovery, Kenso Soai began exploring asymmetric autocatalytic reactions.

He noticed that in a reaction with a pronounced nonlinear effect, the catalyst structure was highly similar to the product structure, which gave rise to the idea of designing an autocatalytic asymmetric reaction.

In 1995, Soai described in a paper the first reaction satisfying all of Frank's conditions: starting with a 5-pyrimidyl alkanol containing a 2% excess of one enantiomer, the excess of that enantiomer rose to 87% after the reaction.

This self-reinforcing reaction came highly close to the theoretical target, but had not yet reached the 100% chiral purity of living organisms.

After another eight years of exploration, Soai reported a milestone result in 2003: starting from achiral molecules, a single chirality could arise spontaneously through randomness alone.

At the beginning of the reaction, both enantiomers were produced, but the tiny difference formed by chance was gradually amplified through the autocatalytic mechanism, and in the end one enantiomer could account for 99.99% of the product.

When the experiment was repeated, which enantiomer "won" depended on the initial random event — this closely simulated the possible mechanism of chiral selection at the origin of life, and was the first time in human history that a complete transformation from achiral to homochiral was achieved in an artificial chemical system.

Real-world value for the pharmaceutical industry

The research results of the two laureates have already had a profound impact on multiple industries.

The nonlinear effect discovered by Kagan is now widely used in pharmaceutical chemistry, helping researchers optimize catalyst design and obtain target enantiomers with higher purity in drug synthesis, fundamentally reducing the risk of a repeat of an event like the thalidomide tragedy.

Flavor and fragrance companies and agrochemical firms have likewise benefited from this theoretical framework.

Although the Soai reaction itself is an artificial system, different from the chemistry of life, it has inspired researchers worldwide to try to synthesize homochiral amino acids and sugars using similar principles, pushing research into the origin of life into a new stage.

Henri B. Kagan was born in 1930 in Boulogne-Billancourt, France, received his doctorate from the Collège de France in 1960, and is now an emeritus professor at Université Paris-Sud.

Kenso Soai was born in 1950 in Hiroshima, Japan, received his doctorate from the University of Tokyo in 1979, and is now an emeritus professor at Tokyo University of Science.