Chemists Win Nobel for One-Handed Molecules

Stockholm — Two chemists who showed how a chemical reaction can be pushed to make only one "hand" of a molecule won the 2026 Nobel Prize in Chemistry on 7 October.

The Royal Swedish Academy of Sciences gave the prize to Henri B. Kagan, born in 1930, of the former Université Paris-Sud in France, and Kenso Soai, born in 1950, of the Tokyo University of Science in Japan, "for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis." Both are now professors emeritus. They will share 12 million Swedish kronor.

Left hands and right hands

Many molecules come in two forms that are mirror images of each other, the way a left hand mirrors a right hand. The two forms are built from the same atoms, joined in the same order, but one cannot be laid exactly on top of the other. Chemists call such molecules chiral, from the Greek word for hand.

Life uses only one hand. The amino acids that make up the proteins in your cells come in two mirror forms, but only one is found in those proteins, the academy said. The sugars in DNA are the same: two forms exist, and life uses one. Scientists call this homochirality, from the Greek for "same" and "hand."

For more than a century this was a puzzle. When chemists ran reactions that could make either hand, they always got an equal mix of both. So how did life end up with only one?

Why it matters for medicine

The puzzle is not only about the origin of life. Many drug molecules also come in two mirror forms. One form has the healing effect, while the other can cause unneeded and sometimes harmful side effects, the academy said. It pointed to thalidomide, a sedative that caused birth defects in thousands of children in the early 1960s; researchers later found the harm came from the mirror-image form of its active ingredient.

So chemists who make medicines want reactions that produce just the right hand. The same goes for makers of flavours, scents, farm chemicals and some new materials, the academy said.

What Kagan found

To make more of one hand, chemists use a catalyst, a substance that speeds up a reaction without being used up. A common type pairs a metal atom with a chiral molecule that steers the reaction toward one hand.

Chemists assumed a simple rule: if the steering molecule in the catalyst was only partly pure, the product would be exactly as pure, no more. In 1986, working at Université Paris-Sud, Kagan showed that this was wrong.

He reasoned that the metal atom grabs two steering molecules at once. With a mix of left and right, that makes three kinds of catalyst: right-right, left-left and left-right. The mixed left-right kind turned out to work far more slowly. That left the "pure" kinds to do most of the work, so the product came out purer than the catalyst that made it. Chemists call this a non-linear effect. It gave them a way to amplify a small lead of one hand into a bigger one.

What Soai found

Soai, at the Tokyo University of Science, took the next step. He looked for a reaction in which the product is also its own catalyst, so that each new molecule helps make more molecules of the same hand. This is called autocatalysis.

In 1995 he described such a reaction using a substance called 5-pyrimidyl alkanol. Starting with a mixture that had just 2 percent more of one hand, he ended with a mixture that had 87 percent more, the academy said.

In 2003 he went further. He started a reaction with ingredients that had no handedness at all. By chance, a tiny excess of one hand formed first, and that excess then copied itself until it made up as much as 99.99 percent of the product. Run it again, and chance might pick the other hand. Other than life itself, no one had done this before, the academy said.

What they said

"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," said Heiner Linke, chair of the Nobel Committee for Chemistry.

Soai was out shopping when he got the news, according to the Royal Society of Chemistry, a British professional body. "This is the most exciting day in my life, I am very glad to share this prize with professor Henri Kagan," he said. "Of course this is not the final answer," he added, saying the field needed more work to understand life.

What changes

The Soai reaction is not how life itself works, but it has sent researchers around the world looking for a similar reaction that makes one-handed amino acids and sugars, the academy said. Kagan's non-linear effects are now a standard tool chemists use to understand and tune reactions so they get the purest possible product.

The chemistry prize is the third of six Nobel announcements running through 12 October. The prizes are presented in December.