Discoveries by two chemists explain how chemical reactions can favour one mirror-image molecule over another, a breakthrough with major importance for making medicines
SRINAGAR: Henri B Kagan of Université Paris-Sud, France, and Kenso Soai of Tokyo University of Science, Japan, have been awarded the 2026 Nobel Prize in Chemistry for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis, the Royal Swedish Academy of Sciences said.
In simpler terms, the two chemists helped solve a mystery that had puzzled scientists for more than a century: how can chemistry produce one particular version of a molecule when two versions are possible?
The question matters because many molecules exist in two forms that are mirror images of each other, rather like a person’s left and right hands. Although the two forms may look almost identical, they can behave very differently inside living organisms.
This is particularly important in medicine. When scientists design drugs, one mirror-image form may produce the desired effect while the other may not. The ability to make predominantly one form is therefore an important part of modern pharmaceutical chemistry.
Mirror Molecules
The phenomenon is known as homochirality.
The word refers to the fact that the chemistry of living organisms overwhelmingly uses one of two possible mirror-image forms. Amino acids, for example, come in two such forms, but only one is normally used in the proteins inside our cells.
For generations, chemists struggled to understand how this preference could arise.
When researchers carried out chemical reactions capable of producing two mirror-image molecules, the normal result was an almost equal mixture of both. Yet nature appeared to have made a decisive choice.
Scientists also wanted to control this choice themselves. Producing one mirror image rather than a 50-50 mixture is particularly valuable when developing substances that interact with living organisms, including medicines.
First Breakthrough
Kagan made the first decisive advance in 1986, when he discovered a new way of manipulating chemical reactions.
According to the Nobel material, his work allowed scientists to obtain a much greater excess of one mirror-image molecule than had previously been thought possible. It was an important step towards understanding and controlling chemical asymmetry.
But a much bigger breakthrough was still to come.
Soai’s Step
In 1995, Soai published a landmark study describing the first chemical reaction with the potential to become homochiral.
His work introduced an unusual feature of chemistry: a reaction in which the products could help drive the reaction towards producing more of the same molecular form.
Eight years later, in 2003, Soai succeeded in demonstrating a reaction in which only one of the two possible mirror-image forms was produced.
The Nobel material describes this as a feat that, apart from life itself, had never previously been achieved.
Chemical Choice
The significance of the work goes beyond producing an interesting laboratory result.
Kagan and Soai’s discoveries showed chemists how homochirality can emerge spontaneously through chemical reactions. Their work provided a way to understand how a chemical system can move away from an equal mixture of two mirror-image forms and favour one of them.
Heiner Linke, chair of the Nobel Committee for Chemistry, said the two scientists had provided a solution to a chemical mystery more than a century old and described their reactions as spectacular.
Medical Value
The discovery is particularly important for pharmaceutical chemistry.
Many medicines work by fitting into specific biological structures in the body. Because mirror-image molecules can interact differently with living systems, being able to manufacture the desired form can be critical to developing effective drugs.
The Nobel Prize organisation says the discoveries of Kagan and Soai have been decisive for chemists designing reactions used in the manufacture of pharmaceuticals.
Their Nobel-winning work therefore addresses a problem that began as a fundamental question about the strange symmetry of molecules but has direct relevance to one of chemistry’s most practical tasks: making useful molecules in the form scientists actually need.
