STOCKHOLM, Sweden — French chemist Henri B. Kagan and Japanese scientist Kenso Soai have won the 2026 Nobel Prize in Chemistry for discoveries that showed how chemical reactions can favour one of two mirror-image forms of a molecule, work that has become crucial to modern drug manufacturing.
The Royal Swedish Academy of Sciences announced the award on Wednesday, October 7, 2026, honouring the pair “for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis.”
Kagan, 95, and Soai, 76, will share the prize of 12 million Swedish kronor, about $1.2 million.
Their research tackled a century-old problem involving chirality, the property that allows molecules with the same chemical composition to exist in two forms that resemble a person’s left and right hands: mirror images that cannot be perfectly superimposed.
That distinction can be critical in medicine because two mirror-image versions of the same molecule can behave very differently inside the human body.
The Royal Swedish Academy of Sciences said the discoveries gave chemists powerful tools for producing the desired version of a molecule and helped explain how living systems could come to favour one molecular “hand” over another.
“Henri Kagan and Kenso Soai have provided a solution to a chemical mystery that is over a century old: how homochirality can emerge spontaneously,” Heiner Linke, chairman of the Nobel Committee for Chemistry, said.
“The chemical reactions they have developed are spectacular.”
Why Molecular ‘Handedness’ Matters
Many important molecules occur naturally in two mirror-image versions, known as enantiomers.
They may look nearly identical chemically but interact differently with biological systems.
Amino acids, for example, can theoretically exist in both forms, yet living organisms overwhelmingly use only one version in proteins. This preference is known as homochirality.
For chemists manufacturing medicines, flavours, fragrances, agricultural chemicals, and other compounds, controlling which molecular form is produced can be essential.
The consequences of failing to distinguish between molecular forms were dramatically illustrated by thalidomide, a sedative prescribed to pregnant women in several countries in the late 1950s and early 1960s.
The drug was associated with severe birth defects in thousands of children.
Research into thalidomide subsequently became an important example of how mirror-image molecules can have dramatically different biological effects.
The Nobel committee said Kagan and Soai’s work gave chemists better ways to understand and control asymmetric reactions, allowing manufacturers to produce purer forms of molecules intended to interact with living organisms.
Kagan Finds a Way to Amplify Molecular Imbalance
Kagan’s breakthrough came in the 1980s as he studied asymmetric chemical reactions at Université Paris-Sud in France.
Chemists were already trying to design reactions that produced more of one enantiomer than the other.
In 1986, Kagan discovered what became known as a non-linear effect.
He demonstrated that even a relatively small imbalance in the molecular form of a catalyst could produce a much larger imbalance in the final product.
The finding showed that chemical systems could amplify small differences in chirality rather than simply reproduce them proportionally.
That insight gave chemists a new way to investigate how asymmetric reactions work and provided tools for improving the purity of substances produced by those reactions.
The academy said non-linear effects are now used by chemists to understand reaction mechanisms and optimise processes designed to obtain the desired molecular form.
Kagan is a professor emeritus at the former Université Paris-Sud and has long been regarded as a pioneer of asymmetric chemistry.
His Nobel recognition comes 25 years after his field was honoured without him.
The 2001 Nobel Prize in Chemistry went to William Knowles, Ryoji Noyori, and K. Barry Sharpless for their work on catalysed asymmetric synthesis.
Kagan’s omission at the time generated debate within the scientific community because of his substantial contributions to the field.
Soai Discovers a Reaction That Copies Itself
Soai took the problem further in the 1990s.
Working at Tokyo University of Science, he investigated whether a chiral molecule could act as a catalyst for producing more molecules with the same handedness.
He eventually discovered an asymmetric autocatalytic reaction — a chemical process in which a product helps generate more of itself.
In an experiment published in 1995, Soai began with only a small excess of one mirror-image form of a molecule called 5-pyrimidyl alkanol.
By the end of the reaction, the imbalance had increased dramatically.
The process became known as the Soai reaction.
It demonstrated that a tiny initial preference for one molecular form could be repeatedly amplified until one version overwhelmingly dominated.
The discovery offered scientists a possible chemical explanation for one of the most enduring questions surrounding the origins of life: how biological systems came to contain almost exclusively one version of certain chiral molecules.
“The Soai reaction is artificial, different to the chemistry of life, but it awakened new enthusiasm in chemists who want to understand life’s origins,” the Royal Swedish Academy said.
Researchers are now exploring whether similar processes could explain how amino acids, sugars, and other molecules essential to life developed their characteristic handedness.
Soai Says Nobel Call Was ‘One of the Most Exciting Days’ of His Life
Soai was outside shopping near his home when he learned that he had won the prize, according to Nature.
“I am very excited to receive the very nice news about the Nobel prize,” he said in a call with the Nobel committee.
“This is one of the most exciting days in my life.”
The academy said Kagan was born in Boulogne-Billancourt, France, in 1930 and earned his doctorate from the Collège de France in 1960.
Soai was born in Hiroshima, Japan, in 1950 and received his doctorate from the University of Tokyo in 1979. He is professor emeritus at Tokyo University of Science.
The two scientists conducted their prize-winning work independently and at different stages, but the Nobel committee said their discoveries together demonstrated mechanisms by which tiny molecular imbalances can become overwhelmingly one-sided.
Their work now underpins techniques used across chemistry, particularly where producing the correct molecular form is essential.
The laureates are scheduled to receive their medals and diplomas at the Nobel Prize ceremony in Stockholm on December 10, the anniversary of Alfred Nobel’s death.
The chemistry award follows the Nobel Prize in Physiology or Medicine on Monday and the Nobel Prize in Physics on Tuesday.
