Nobel Prize in Chemistry awarded to Kenso Soai and partner for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis

The Royal Swedish Academy of Sciences (RSAS) announced on October 7 that it will award the 2026 Nobel Prize in Chemistry to Emeritus Professor Kenso Soai (76) of Tokyo University of Science and Emeritus Professor Henri Kagan (95) of Paris-Sud University in France. The citation for the award reads "for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis." The Academy recognized their development of specialized reactions that selectively amplify specific chiral forms during catalyst-driven asymmetric synthesis. Soai became the 10th recipient of the Nobel Prize in Chemistry from Japan, following Susumu Kitagawa last year.

Synthesizing molecules such as amino acids through chemical reactions can yield two types of "enantiomers," structures that relate as mirror images to each other. However, biological organisms contain only one of these forms, and why this asymmetry known as "homochirality" arose remained a mystery. Furthermore, as seen in tragic side effects of the sedative thalidomide, while one enantiomer has therapeutic effects, the other form may prove ineffective or occasionally trigger harmful side effects. Some molecules such as amino acids possess two enantiomers that exist as mirror images of each other.

Researchers considered that generating homochirality required three conditions: (1) catalysts driving reactions that produce primarily one enantiomer, (2) reactions producing one enantiomer accelerating while reactions producing the other enantiomer suffer suppression, and (3) autocatalysis functioning as chemical reactions proceed to amplify only one enantiomer. In 1986, Kagan discovered a new method to manipulate chemical reactions, succeeding in generating larger proportions of single enantiomers than previously thought possible, which confirmed condition (2).

While researching asymmetric chemical reactions that produce imbalances in product yields, Soai analyzed the structures of catalysts and products during reactions. From their structural similarities, he considered whether he could design reactions where products themselves act as autocatalysts to synthesize more of the same product. After conducting repeated experiments using various molecules, he designed and published his unique "Soai reaction" in 1995. In 2003, he succeeded in generating enantiomeric excesses and further amplifying them in an autocatalytic manner.

Regarding the Soai reaction, RSAS praised it highly, stating that "it represents one of the most astonishing achievements in chemical experimentation." Praising the accomplishments of Soai and Kagan, RSAS stated that "they provided a solution to the question of how homochirality arose spontaneously, a problem that remained unsolved for over a century."

Soai joined the press conference of the RSAS by telephone, stating his impressions: "This is one of the most exciting days of my life, and I'm very glad to share the prize with Professor Henri Kagan, a renowned authority in organic chemistry."

The two recipients will divide the prize money of 12 million Swedish kronor (approximately 190 million yen) equally. The award ceremony will take place in Sweden on December 10.