Kagan and Soai win Nobel Prize in chemistry for solving a century-old puzzle of molecular handedness

The Royal Swedish Academy of Sciences on Wednesday awarded the 2026 Nobel Prize in Chemistry to Henri B. Kagan, a 95-year-old French chemist, and Kenso Soai, a Japanese chemist born in Hiroshima in 1950, for discoveries that let researchers force a chemical reaction to build only one of two possible mirror-image versions of a molecule. The academy said in its official citation that the two laureates were honored "for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis."

The announcement, made in Stockholm shortly before 6 a.m. Eastern time, resolves what the committee called a mystery that had puzzled chemists for more than a century: how living organisms ended up using only one of the two mirror-image forms that most of their essential molecules can take. Kagan and Soai, working decades and continents apart, each supplied a piece of the answer.

The Numbers

The prize carries 12 million Swedish kronor, worth roughly $1.7 million at current exchange rates, to be split evenly between the two laureates. Kagan, who spent most of his career at Université Paris-Sud in Orsay, outside Paris, is recorded in the Nobel Foundation's biographical note on his work as having earned his doctorate in 1960 from the Collège de France and as holding emeritus status at the university. Soai, whose career was built at the Tokyo University of Science, is listed in a companion biography published by the foundation as having received his doctorate from the University of Tokyo in 1979.

Two dates anchor the science. In 1986, Kagan discovered what chemists call non-linear effects: he showed that a reaction could be engineered to produce a greater excess of one mirror-image molecule than the purity of the catalyst used to make it, a result many chemists had assumed was impossible. Nine years later, in 1995, Soai published a reaction design built to amplify tiny chemical imbalances on its own. He spent eight more years refining it before succeeding, in 2003, in building a reaction in which only one of the two possible mirror-image products formed at all, a feat the academy's committee describes as unmatched outside living organisms.

A Puzzle Dating to Pasteur

Many molecules, including amino acids and the sugars in DNA, can exist in two forms that are mirror images of each other, the way a left hand mirrors a right hand. Chemists call this property chirality, and a molecule's two mirror-image versions are enantiomers. Living cells, however, are strictly one-handed: proteins are built almost exclusively from left-handed amino acids, while the sugar backbone of DNA is right-handed. Scientists have called this asymmetry homochirality since the French chemist Louis Pasteur first showed, in the mid-19th century, that crystals of tartaric acid come in two mirror-image forms and that fermenting bacteria would consume only one of them while ignoring the other entirely.

A more technical account published by the academy alongside the announcement traces the century and a half of research that followed Pasteur's observation, as chemists tried and failed to design laboratory reactions that would favor one enantiomer over the other the way nature does. Ordinary chemistry, left to its own devices, almost always produces equal amounts of both mirror images, a mixture chemists call racemic. Kagan's and Soai's work, taken together, gave chemists the first reliable tools to break that symmetry deliberately.

Who Is Affected

The practical stakes are largest in the pharmaceutical industry, where a drug's two enantiomers can behave very differently inside the body. One mirror image of a molecule may produce the intended therapeutic effect while its twin does nothing or causes harm, so manufacturers increasingly need reactions that yield only the useful form rather than a wasteful, and sometimes dangerous, 50-50 mixture. The effect is not limited to medicine: the molecule carvone, as the Australian Broadcasting Corporation explained in its coverage of the prize, smells of spearmint in one mirror-image form and of caraway seed in the other, a vivid illustration of how completely a molecule's handedness can change its behavior.

Peter Somfai, a member of the Nobel Committee for Chemistry, was asked on the day of the announcement to name a specific drug that depended on the laureates' methods. He said it was difficult to single one out: "I would say all of them, because we use this as a tool," underscoring how thoroughly the techniques have been absorbed into routine pharmaceutical chemistry rather than reserved for a handful of landmark products.

Reaction From Stockholm and Beyond

Heiner Linke, who chairs the Nobel Committee for Chemistry, framed the discoveries as the resolution of one of chemistry's oldest open questions.

"Henri Kagan and Kenso Soai have provided a solution to a chemical mystery that is over a century old: how homochirality can emerge spontaneously. The chemical reactions they have developed are spectacular," Linke said.

Soai, reached shortly after the announcement, described his own reaction in personal terms. Scientific American reported that he called it "one of the most exciting days in my life" and added that he was "very glad to share the prize with Professor Henri Kagan." Asked whether his work explained how life itself first became one-handed, Soai was cautious, saying only "this is not the final answer" and that the field needed to keep advancing before that deeper question could be settled. Somfai, by contrast, was more willing to speculate that the discoveries could eventually help explain how life arose on Earth, telling reporters that Soai's self-amplifying reaction showed, for the first time, how a single mirror-image form could emerge essentially "from nothing."

Rigoberto Hernandez, president of the American Chemical Society, offered an outsider's appraisal of why the work mattered, comparing molecular chirality to two dancers who have to move in matching orientation. "You need to have just the right fit and relative orientation," he said, adding that the prize illustrated how decades-old basic research continues to underpin practical chemistry today and that sustained investment in fundamental science was what made discoveries like Kagan's and Soai's possible in the first place.

The award extends a line of Nobel recognition for work on molecular handedness. In 2001, the chemistry prize went to William Knowles, Ryoji Noyori and K. Barry Sharpless for chirally catalyzed reactions, and in 2021 it went to Benjamin List and David W.C. MacMillan for a related technique called asymmetric organocatalysis, as the academy's own archive of chemistry laureates shows. Kagan's and Soai's prize fills in an adjacent, longer-standing gap in that same field: not how to steer a reaction toward one enantiomer with an external catalyst, but how a reaction can amplify a one-handed outcome on its own.

What Happens Next

The chemistry announcement was the third of six Nobel Prizes being unveiled this week, following prizes in medicine and physics earlier in the week and preceding announcements in literature, peace and economic sciences before the cycle closes. NPR's coverage of Wednesday's announcement noted that the Chemistry Prize has now been awarded, with only a handful of interruptions, every year since 1901, when Jacobus Henricus van 't Hoff became its first recipient; Marie Curie remains the only woman to have won it, taking her second Nobel Prize in chemistry in 1911 after winning in physics eight years earlier.

Kagan and Soai are expected to travel to Stockholm in December to receive their medals, diplomas and share of the prize money at the formal award ceremony held each year on December 10, the anniversary of Alfred Nobel's death. Between now and then, the two chemists are likely to face a round of academic lectures, interviews and tributes from the pharmaceutical and fine-chemicals industries that have relied for years on methods tracing back to their laboratories, even as researchers studying the origin of life continue to debate, as Soai himself suggested, how much further work is still needed before the deeper question of why life chose one hand over the other is finally settled.