Chemistry nobel rewards the mirror-image solution

By Daniel Okafor · Reporting from New York · October 7, 2026

Henri B. Kagan and Kenso Soai won the Nobel prize in chemistry for solving how molecules form mirror images.

The century-old mirror

Louis Pasteur watched tartaric acid crystals under his lens in the mid-1800s. The French chemist found that bacteria fermented only one type of sugar molecule in sweet tartaric acid from grapes and left the mirror image untouched. That observation proved that molecules exist in two forms containing the same atoms but facing opposite directions.

Living organisms use almost exclusively one version of these shapes. Proteins are built almost exclusively from left-handed amino acids and DNA and RNA sugars have the right-handed configuration. Scientists call this phenomenon homochirality, derived from Greek words for "same" and "hand."

For more than a century, researchers did not know how that single-handedness emerged spontaneously in nature. The Royal Swedish Academy of Sciences awarded the 2026 Nobel prize in chemistry to Henri B. Kagan and Kenso Soai on Wednesday in Stockholm, Sweden, for solving that exact puzzle. The committee cited the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis.

Heiner Linke, chair of the Nobel Committee for Chemistry, said that Henri Kagan and Kenso Soai provided a solution to a chemical mystery that is over a century old. He called the chemical reactions they developed spectacular, according to reporting by DW and NPR.

Kagan is a 95-year-old Frenchman affiliated with Université Paris-Sud. Soai is a 76-year-old Japanese chemist based at the Tokyo University of Science. The laureates will each receive an equal share of 12 million Swedish kronor, approximately $1.2 million.

Amplifying the small imbalance

Molecules can look identical on paper yet act differently in practice. Prof Andre Cobb, an organic chemist at King’s College London, told The Guardian that although these molecules look very similar, they can behave very differently when they interact with other molecules.

That difference shapes human medicine. Many molecules in the human body, including proteins that drugs target, are chiral. The left-handed and right-handed versions of a drug interact with the body in different ways, which can lead to different or weakened drug effects.

The consequences of ignoring this molecular geometry turned catastrophic during the Thalidomide scandal in 2006. The sedative caused birth defects in thousands of children because its two mirror-image forms had different biological effects, with the mirror image of the active substance causing the harm. Rappler and SVT Nyheter note that the drug caused conditions including short arms and damaged hands.

Kagan cracked part of this puzzle in 1986. He discovered that a small imbalance between left- and right-handed catalyst forms could create a greater excess of one mirror-image product, according to The Guardian.

Soai then built the mechanism that amplified that imbalance into complete dominance. In organic chemistry, the Soai reaction is the alkylation of pyrimidine-5-carbaldehyde with diisopropylzinc. The reaction is autocatalytic and leads to rapidly increasing amounts of the same enantiomer of the product.

The product pyrimidyl alcohol is chiral and induces that same chirality in further catalytic cycles. Starting with a low enantiomeric excess produces a product with very high enantiomeric excess. This uses autocatalysis to amplify a small imbalance into a single mirror-image molecular form.

In 2003, Soai demonstrated a reaction that produced almost exclusively one mirror-image form. Prof Peter Somfai, an organic chemist at Lund University and a member of the Nobel committee, told The Guardian that it is probably the coolest experiment in organic chemistry ever.

Soai expressed his joy when the academy announced the award. He said he was very proud and called it one of the most exciting days of his life.

The long delay ends

Some critics might argue that fundamental organic chemistry has little bearing on the industrial production of pharmaceuticals. The evidence from the Nobel committee dismantles that objection entirely.

The discoveries have been decisive for chemists who design reactions for the manufacture of pharmaceuticals. Somfai explained to Rappler that the left-handed version of a drug can have one effect while the right-handed version has another, requiring methods for selectively preparing them.

The laureates provided powerful tools for that work. Somfai noted that chemists use this understanding as a tool to develop catalysts and govern how they function.

This recognition also corrects a historic oversight echoing the Nobel Prize in Chemistry 2001. In that year, the prize went to other researchers for asymmetric hydrogenation, while Kagan, widely considered the father of the asymmetric catalysis technique, was passed over to the point that the French Ministry of Research protested.

The Royal Swedish Academy of Sciences has now corrected that record. Ellen Moons, permanent secretary of the academy board, said that this year's prize is about getting chemistry to choose a mirror image, according to SVT Nyheter.

Kagan and Soai solved how nature chose its hand, giving modern medicine the tools to do the same safely.

Chemistry nobel rewards the mirror-image solution

The century-old mirror

Amplifying the small imbalance

The long delay ends

Sources