The Royal Swedish Academy of Sciences has awarded the Nobel Prize in Chemistry 2026 to Henri B. Kagan of Université Paris-Sud, France, and Kenso Soai of Tokyo University of Science, Japan, for their discoveries explaining how chemical homochirality can emerge spontaneously. Their work addresses a long-standing question in chemistry: why do living organisms predominantly use only one of two mirror-image forms of certain molecules?
Solving the Mystery of Chemical Handedness
Some molecules, including amino acids, exist in two forms that are mirror images of each other. Chemists call these forms enantiomers. Although both forms can exist, living organisms primarily use only one of them. This phenomenon is known as homochirality, derived from Greek words meaning “same” and “hand”. The concept is similar to human hands: the left and right hands mirror each other but cannot be perfectly superimposed. For decades, scientists struggled to understand how this chemical asymmetry could arise naturally.
From Equal Mixtures to Chemical Asymmetry
Chemical reactions that produce mirror-image molecules typically generate both forms in equal proportions. However, producing predominantly one enantiomer is particularly important when developing molecules that interact with living systems. This is especially relevant to pharmaceutical development, where the two mirror-image forms of a molecule can have significantly different biological effects. Kagan and Soai’s research demonstrated how chemical reactions can overcome this symmetry and favour the formation of one mirror-image molecule.
Kagan’s Breakthrough in 1986
Henri B. Kagan made the first decisive contribution in 1986, when he discovered a new method for controlling chemical reactions. His work enabled chemists to produce a significantly greater excess of one mirror-image form than previously thought possible. This discovery opened a new pathway for studying and controlling chemical asymmetry.
Soai Achieves Homochiral Reaction
Kenso Soai subsequently advanced the field. In 1995, he published a landmark study describing a chemical reaction with the potential to become homochiral. Then, in 2003, Soai achieved a major breakthrough by demonstrating a reaction in which only one of the two possible mirror-image forms was produced. According to the Nobel Committee, no one other than living organisms had previously achieved this feat.
Impact on Pharmaceutical Chemistry
The discoveries of Kagan and Soai have provided an important explanation for how homochirality can emerge spontaneously. Their work has also influenced modern synthetic chemistry, particularly the design of reactions used to manufacture pharmaceuticals. By enabling chemists to control molecular handedness, these discoveries have helped advance the development of more precise and effective chemical processes. As per the Nobel Prize press release, as Nobel Committee for Chemistry chair Heiner Linke noted, the researchers have provided a solution to a chemical mystery that has challenged scientists for more than a century.
