2026 Nobel Prize in Chemistry Honors Henri Kagan and Kenzo Soai for Explaining Molecular “Handedness”

Henri Kagan and Kenzo Soai have been awarded the 2026 Nobel Prize in Chemistry for explaining why some chemical reactions produce molecules in just one of two possible mirror-image forms.

On October 7, the Royal Swedish Academy of Sciences in Stockholm announced that Kagan, of the University of Paris-Sud in Orsay, France, and Soai, of the University of Tokyo, will share the 12 million Swedish kronor (US$1.2 million) prize.

“I’m very excited to hear the very good news about the Nobel Prize. It’s one of the most exciting days of my life,” Soai told the Nobel Committee after the award was announced. He added that he was shopping near his home when he received the call.

Although molecules can occur in either form, the building blocks of life are usually one-handed, or “homochiral.” DNA is right-handed, for example, whereas human amino acids are left-handed. The researchers’ work addresses the long-standing question of how this chemical asymmetry emerges in nature.

In experiments conducted in the 1980s, Kagan showed how small differences in the handedness of a catalyst can be amplified in the reaction products.¹ In 1995, Soai designed a reaction in which the chiral product also acted as the catalyst, further increasing the asymmetry.² Together, the studies suggest how natural reactions in living organisms could overwhelmingly produce just one type of mirror-image molecule.

“Henri Kagan and Kenzo Soai have provided a solution to more than a century of chemical puzzles: how homochirality emerges spontaneously,” Heiner Linke, chairman of the Nobel Committee for Chemistry, said in a statement. “The chemistry they developed is amazing.”

“Kagan was a very, very humble person with a real passion for chemistry, and he didn’t care about fame,” says Olivier Lien, an organometallic chemist at the University of Louvain in Louvain-la-Neuve, Belgium, who was a doctoral student in Kagan’s laboratory at the University of Paris-Sud.

Today, this discovery is important for chemists designing reactions to create drugs, materials and perfumes. The winners’ discoveries “challenge what we thought we knew and open up entirely new ways of thinking and designing chemical reactions,” says Mónica Pérez Temprano, a mechanistic chemist at the Catalunya Institute of Chemistry in Tarragona, Spain.

The century-old puzzle of molecular handedness

Chemists have long known that some molecules exist as two mirror images, or chiral forms, known as enantiomers. Life often functions using only one of these forms. Yet when chemists run reactions that produce chiral molecules, they typically obtain a mixture of both types. How organisms create just one mirror image has therefore remained a fundamental puzzle.

Catalysts—substances that accelerate chemical reactions without being used up—quickly emerged as a possible key. If a catalyst is itself chiral, it can promote the formation of one mirror-image molecule over the other. In 1953, Charles Frank, a theoretical physicist at the University of Bristol in the United Kingdom, proposed that if a chemical reaction could produce its own chiral catalyst, it would create a self-reinforcing effect in which one mirror image became dominant.³

William Knowles, Ryoji Noyori and Barry Sharpless, who shared the 2001 Nobel Prize in Chemistry, designed reactions that use chiral catalysts to direct chemical reactions and produce mainly one version of a molecule. The 2026 award recognizes Kagan and Soai for going further and making Frank’s vision a reality by engineering a reaction that creates a unique chiral catalyst.

“Kagan showed how it could be done in principle, and then the Soai reaction gave us the first real example,” says Jonathan Craden, an organic chemist at the University of Bristol.

Stephen Fletcher, a synthetic chemist at the University of Oxford in the United Kingdom, says Soai has “done a fantastic job of tuning the autocatalytic reaction.” In chemical mixtures, “in some cases, you might have a million one-handed molecules on one side and a million-and-one other-handed molecules on the other side. Soai then worked on ways to amplify that imbalance, which is remarkable.”

Kagan and Soai’s work has attracted interest from researchers trying to explain why biological molecules such as amino acids and nucleic acids tend to exist in just one chiral form, says Furkan Ozturk, a geochemist at the California Institute of Technology in Pasadena who studies the chemistry of the origins of life.

Since the Soai reaction was discovered, scientists have been investigating whether similar reactions could have occurred on the “prebiotic” Earth, before life arose. The reaction cannot be carried out in water and requires reagents that are not well suited to prebiotic Earth conditions or chemical inventories. Nevertheless, its basic principles could help researchers understand the origins of prebiotic homochirality, Ozturk says.

“Many people are trying to study the biological relevance of autocatalytic reactions, and I can see this award being the spark that will reignite this research,” Fletcher says.

Kagan’s pioneering experiment and the Soai reaction

Kagan was the first to discover a reaction in which a small initial imbalance in the chirality of a catalyst is amplified during the experiment. The result is a larger imbalance between the two types of chiral catalyst.

Soai then searched for other reactions with this asymmetric effect and, importantly, for reactions in which the catalyst forms part of the reaction itself. This process is known as autocatalysis.