Henri B. Kagan of Université Paris-Sud in France and Kenso Soai of Tokyo University of Science in Japan were awarded the 2026 Nobel Prize in Chemistry on Wednesday for their discovery of non-linear effects and autocatalysis in asymmetric organic synthesis.
The Royal Swedish Academy of Sciences said their work provided a solution to a chemical mystery that has puzzled scientists for more than a century: how homochirality, or the dominance of one mirror-image form of a molecule, can emerge spontaneously.
The discoveries are particularly important for understanding the chemistry of life and for designing chemical reactions used to manufacture pharmaceuticals.
Why mirror-image molecules matter
Some molecules, including amino acids, can exist in two forms that are mirror images of each other. This property is known as chirality, a term derived from the Greek word for “hand”.
Like the left and right hands, the two forms contain the same atoms but have different three-dimensional arrangements and cannot be perfectly superimposed.
In most chemical reactions capable of producing such molecules, there is no obvious reason for one mirror image to dominate. Chemists therefore generally obtained roughly equal quantities of both forms.
Life, however, appears to have made a very different choice.
All amino acids have two mirror-image forms, but living organisms overwhelmingly use only one of them in their proteins. The other form is rarely found in nature.
This phenomenon is known as homochirality, derived from Greek words meaning “same” and “hand”. How this chemical preference arose has remained one of chemistry’s longstanding mysteries.
Kagan showed how an imbalance could emerge
The first decisive step towards solving the puzzle came from Kagan in 1986.
He discovered a new way of manipulating chemical reactions that could produce a much greater excess of one mirror-image form than scientists had previously believed possible.
The finding challenged the conventional expectation that reactions producing two mirror-image molecules would result in approximately equal proportions.
But a crucial question remained: could a small initial imbalance be amplified until virtually one form dominated?
That was the problem Soai subsequently tackled.
Soai demonstrated the power of autocatalysis
In 1995, Soai published a key study describing a chemical reaction with the potential to become homochiral.
Its central feature was autocatalysis, a process in which a product of a chemical reaction helps catalyse the formation of more of that same product.
Such a mechanism provides a way for a small chemical advantage to reinforce itself. If one mirror-image form gains even a slight lead, the reaction can amplify that advantage, allowing one form to increasingly dominate over the other.
In 2003, Soai demonstrated a reaction in which only one of the two possible mirror-image forms was produced. He created chiral molecules from a non-chiral mixture and succeeded in producing only one of the two mirror images.
According to the Royal Swedish Academy of Sciences, no one other than life itself had previously achieved this feat.
Why the discovery matters for medicines
The ability to control which mirror-image form of a molecule is produced is particularly important in pharmaceuticals.
Two mirror-image versions of the same molecule can interact differently with living organisms and can therefore have different effects in the body. Being able to favour one form allows chemists to design reactions that produce molecules with the desired properties.
The Nobel committee said Kagan and Soai had therefore provided an answer to the question of how homochirality can arise and made discoveries that have been decisive for chemists designing reactions for pharmaceutical manufacturing.
Kagan and Soai among 2026 Nobel laureates
Kagan, born in 1930 in Boulogne-Billancourt, France, earned his doctorate from the Collège de France in 1960 and later became professor emeritus at the former Université Paris-Sud.
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 2026 Chemistry Nobel carries a prize amount of 12 million Swedish kronor, to be shared equally between the two laureates.
Their work has thus turned a fundamental puzzle about the chemistry of life into a phenomenon that chemists can understand and, crucially, control.