The 2026 Nobel Prize in Chemistry goes to two chemists who uncovered surprising ways molecules can pass on, and even amplify, their “handedness.”
The Royal Swedish Academy of Sciences on Wednesday awarded the prize to Henri B. Kagan of France and Kenso Soai of Japan “for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis.” They will share 12 million Swedish kronor, about $1.2 million.
First, what is molecular “handedness”?
Many molecules come in two mirror-image versions, like a left and a right hand. The two versions contain the same atoms but are arranged differently in space, and chemists call this property chirality.
That difference can matter enormously, especially for medicines, because the human body is built from chiral molecules and can react very differently to each version. The best-known example is thalidomide: one form of the drug works as a sedative, while its mirror image causes severe birth defects. With the tuberculosis drug ethambutol, the active form is about 500 times more potent than its mirror image, which can cause blindness. Today, drug companies and regulators strongly favor medicines made of just one version.
“Asymmetric synthesis” is the art of making mostly one hand rather than a 50-50 mix. That’s where this year’s laureates come in.
Kagan: when the math doesn’t add up
Chemists often use a chiral catalyst, a helper molecule that steers a reaction toward one hand of the product. The common assumption was simple: if your catalyst is only, say, 70% pure in one hand, your product will be proportionally less pure too.
In 1986, Kagan and his co-workers showed that assumption doesn’t always hold. In a series of known reactions, the purity of the product didn’t track the purity of the catalyst in a straight line. Sometimes the product came out purer than expected, an effect now called asymmetric amplification. Sometimes it came out less pure. Kagan also built mathematical models to explain why.
These “non-linear effects” gave chemists a new tool for understanding how catalysts really behave, and for designing better ones.
Kagan, born in 1930 in Boulogne-Billancourt, near Paris, is an emeritus professor at Université Paris-Sud in Orsay. He was also an early pioneer of asymmetric catalysis more broadly, developing a family of catalyst components known as DIOP ligands. When the 2001 chemistry Nobel went to three other pioneers of the field, his omission drew criticism; 25 years later, at 95, he has his own.
Soai: a molecule that copies its own hand
In 1995, Soai, a chemist at the Tokyo University of Science, discovered a reaction that now bears his name. In the Soai reaction, the product acts as a catalyst for making more of itself, a process called autocatalysis. Crucially, it tends to make more of whichever hand it already is.
The result is dramatic amplification. Starting from a tiny imbalance between the two hands, repeated rounds of the reaction can produce an almost perfectly one-handed product. In a 2019 review, Soai and colleagues described starting from an excess of about 0.00005% and ending above 99.5%, an amplification of roughly 630,000 times.
Soai earned his Ph.D. at the University of Tokyo in 1979 and did postdoctoral work at the University of North Carolina. His earlier honors include Japan’s Purple Ribbon Medal in 2012.
A clue to one of life’s mysteries
Soai’s discovery also speaks to a deep question about the origin of life. The amino acids in our proteins and the sugars in our DNA are almost all one-handed. Nobody knows for sure how life ended up that way, a puzzle that dates back to Louis Pasteur’s discovery of molecular chirality in 1848.
Soai’s team showed that very small nudges could tip his reaction toward one hand, including circularly polarized light and chiral minerals such as quartz. That offers a plausible chemical route by which a tiny, random imbalance on the early Earth might have snowballed into the one-handed chemistry of living things.
The two discoveries are linked. Researchers later used Kagan’s models to help explain how amplification works in the Soai reaction.
The catch
The Soai reaction is a specific, carefully controlled chemical system. It shows how one-handed chemistry could emerge from tiny imbalances, but it doesn’t prove this is how life actually began. Scientists continue to debate the origins of life’s handedness.
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Sources
- AP (via WSB-TV): Nobel Prize in chemistry awarded to Henri B. Kagan and Kenso Soai
- Devdiscourse: Kagan and Soai win 2026 Nobel chemistry prize
- Symmetry (MDPI): Role of asymmetric autocatalysis in the elucidation of origins of homochirality of organic compounds
- Wikipedia: Henri B. Kagan
- Wikipedia: Soai reaction
- Wikipedia: Non-linear effects
- Wikipedia: Chiral drugs