Nobel in chemistry for the detectives of nature's asymmetry

BarcelonaIf two molecules are practically identical, why does nature end up favoring one? To understand this phenomenon, which is known as homochirality, we can do an imaginative exercise with a pair of shoes: the right and the left are mirror images of each other—as if one were the reflection of the other in a mirror—but they cannot be swapped because each one fits a different foot. With some molecules, such as amino acids, the same thing happens: they exist in two forms that have the same composition and structure, but which cannot be superimposed. They are the so-called chiral molecules.

The origin of this chemical asymmetry was for a long time a mystery. Now it is known that a small initial difference between these two forms can eventually be amplified until one of them ends up predominating. It is this advance in the understanding of chemical asymmetry that the Royal Swedish Academy of Sciences recognized this Wednesday with the 2026 Nobel Prize in Chemistry. The award has distinguished Kenso Soai, a Japanese professor at the Tokyo University of Science, for performing "one of the most spectacular chemical experiments ever done," as well as Henri Kagan, a French professor at the University of Paris-Sud.

In a statement, the institution recognizes the trajectory of the two scientists for "their contribution to the understanding of chemical asymmetry through non-linear effects and autocatalysis in asymmetric organic synthesis." For years, getting a chemical reaction to produce only one of the two mirror forms seemed almost impossible. When scientists tried to create them, they usually obtained a mixture of both in similar proportions in their test tubes. But only one of them is found predominantly in the proteins of our cells; the other is very rare in living beings.

However, the problem was not just a question of laboratory precision: if the molecules were intended to interact with living beings, as is the case with medicines, the two forms could behave differently: each one could produce a different effect, even an undesirable one. "That is why we need methods to prepare them selectively," argues Peter Somfai, a member of the Swedish Academy.

The "genius" of two scientists

Kagan took the first major step in 1986: he discovered a way to amplify one of the two forms and obtain an excess much greater than what was previously considered possible. A few years later, Soai took this idea even further and in 1995 described a reaction with the potential to favor a single form. Almost a decade later, in 2003, Soai demonstrated that it was possible to arrive at forming practically only one of the two molecules. A milestone that, until then, seemed reserved for the chemistry of life.

Since then, these discoveries have become fundamental for designing reactions capable of producing chiral molecules with applications in drugs, aromas and fragrances, agricultural chemicals, and new materials. In fact, the Professor of Organic Chemistry at the Complutense University of Madrid and full academician of the Royal Academy of Sciences, Nazario Martín, considers it a “magnificent” Nobel, which stands out for the “brilliance” of the laureates: "It really provides an answer to one of the great questions of science: why is nature chiral? The answer was there and only they saw it," he states in statements to SMC Spain.

"Those of us who work in this field feel this recognition as something very close," adds Raquel Pérez Herrera, a research scientist at the Institute of Chemical Synthesis and Homogeneous Catalysis (ISQCH, Unizar-CSIC), where she is the principal investigator of the Asymmetric Organocatalysis group.