Kagan and Soai share the chemistry Nobel for one-handed molecules

Two chemists who chased one-handed molecules share the 2026 prize

Henri Kagan and Kenso Soai were awarded the 2026 Nobel Prize in Chemistry on Wednesday for the discovery of nonlinear effects and autocatalysis in asymmetric organic synthesis. The Royal Swedish Academy of Sciences announced the prize in Stockholm at 9:51 UTC. The two men share 12 million Swedish crowns, about 1.2 million dollars.

Kagan is 95 and a professor emeritus at Université Paris-Sud, now part of Paris-Saclay. Soai is 76 and works at the Tokyo University of Science. Soai told the prize news conference he had been out shopping when the call came. “This is the most exciting day in my life, I am very glad to share this prize with Professor Henri Kagan,” he said.

The citation is narrow, and that is the useful part. The academy did not honour a new drug or a new machine. It honoured a pair of findings about how a reaction can be pushed toward one molecular mirror image and away from the other.

Why the left hand and the right hand are not the same drug

Many molecules that matter in a body exist as a pair of mirror images. Chemists call them enantiomers. They have the same atoms and the same bonds, and they cannot be laid on top of each other, any more than a left glove can be made to fit a right hand by turning it over on a table.

In a medicine, that difference can decide the effect. Peter Somfai, a member of the Nobel Committee for Chemistry, put it in plain terms at the announcement: the left-handed version of a drug can have one effect, and the right-handed version can have another, so chemists need methods for preparing one of them on purpose. He said the laureates had supplied powerful tools for that work, and he called the key experiment “probably the coolest experiment in organic chemistry.”

The committee used the thalidomide scandal of the early 1960s as the cautionary case. The sedative was sold as a mixture. One mirror image of the active substance was tied to the birth defects that harmed thousands of children. Selective preparation, on this reading, is a manufacturing problem as much as a classroom diagram.

What Kagan and Soai actually showed

Kagan has worked on chirality since the 1960s. His name has sat beside the field of asymmetric synthesis for decades. In 2001 the chemistry prize went to William Knowles, Ryoji Noyori and Barry Sharpless for catalytic asymmetric synthesis. The French research minister at the time complained to the Nobel Foundation that Kagan had been left out. Wednesday’s award does not rewrite 2001. It marks a different slice of the same problem: nonlinear effects, in which a small excess of one mirror image can be amplified, and autocatalysis, in which a product of the reaction speeds the reaction that makes more of itself.

Soai’s reaction, studied from the 1990s, became the textbook case of an autocatalytic system that can grow a tiny imbalance into a large one. A flask that starts almost even can finish strongly biased toward one hand. That is the point Somfai was pointing at when he spoke of making one mirror image “from nothing,” meaning from a trace imbalance rather than from a large charge of an already pure catalyst.

The academy said the discoveries are decisive for chemists who design reactions for the manufacture of pharmaceuticals. That sentence is doing real work. A plant that can run a reaction toward one enantiomer uses less feedstock, runs fewer separation steps, and throws away less of the unwanted twin. The prize money is shared. The industrial consequence is not shared equally across every drug. It shows up where the unwanted mirror image is toxic, inactive, or expensive to remove.

What the winners said, and what the prize does not settle

Kagan’s daughter, Veronique Le Deunff, said the family was very happy, and that the creativity and originality of his work had opened new avenues for research. Soai, speaking from Tokyo, was careful about the remaining gap. He said the mystery of mirror-image molecules had not been fully unravelled, and that he intended to keep working on it.

The prize follows this week’s medicine and physics announcements. Chemistry is the third science prize of Nobel week, with the literature, peace and economics prizes still to come. Kagan’s age, 95, makes him one of the older laureates in the chemistry list. Soai, at 76, is closer to the recent average.

A reader who already knows the headline still needs three numbers and one distinction. The sum is 12 million crowns. The ages are 95 and 76. The 2001 prize was for catalytic asymmetric synthesis and did not include Kagan, despite a formal French complaint. Wednesday’s citation is for nonlinear effects and autocatalysis, which is a different claim: a small chiral imbalance can be grown, and a product can catalyse its own formation. That is the part a process chemist can take back to a plant.