Kagan and Soai win chemistry Nobel for asymmetric synthesis

Henri B. Kagan and Kenso Soai won the Nobel Prize in Chemistry on Wednesday for discoveries that show how a chemical reaction can favor one version of a molecule over its mirror image — and, in some cases, produce only that version.

The Royal Swedish Academy of Sciences announced the award in Stockholm, recognizing the scientists’ work on non-linear effects and autocatalysis in asymmetric organic synthesis. Their discoveries address a longstanding question about homochirality: how the selective production of one molecular form can arise spontaneously.

“Henri Kagan and Kenso Soai have provided a solution to a chemical mystery that is over a century old: how homochirality can emerge spontaneously,” Heiner Linke, chair of the Nobel Committee for Chemistry, said in a statement. “The chemical reactions they have developed are spectacular.”

Many organic molecules come in two forms that are mirror images of each other, much like a person’s left and right hands. Chemists call this property chirality. Amino acids, the building blocks of proteins, have such forms, but living organisms use only one of them. Ordinary laboratory reactions, by contrast, often produce an even mix of the two.

That difference matters in drug development. Mirror-image versions of a molecule can interact differently with the body: One may fight disease while the other has no effect or causes harm. The Nobel committee said Kagan and Soai’s discoveries have been decisive for chemists designing reactions to manufacture pharmaceuticals.

According to the BBC, Kagan found a new way to manipulate chemical reactions in 1986, producing a greater excess of one mirror-image form than had previously been thought possible. Soai advanced that work in 1995, publishing a paper in Nature describing a reaction with the potential to produce only the desired form of an organic molecule. In 2003, the BBC reported, he controlled a reaction that formed just one of the two possible mirror images.

“Other than life itself, no one had previously achieved this feat,” the Nobel committee said, according to the BBC. NPR reported that the experiment is known as the “Soai reaction.”

Kagan, who was born in France, is affiliated with Université Paris-Sud in Orsay. Soai, who was born in Japan and is affiliated with the Tokyo University of Science, is 95, according to NPR. Speaking by phone at the Nobel press conference, Soai said: “This is one of the most exciting days of my life.” He also praised the “many, many excellent researchers” working in the field, the BBC reported.

Robert Mokaya, president of the UK’s Royal Society of Chemistry, called the work a “powerful example of how fundamental chemistry can underpin solutions to some of the biggest challenges facing society.” Different versions of molecules, he said, can have “completely different biological and physical effects.”

The prize carries 12 million Swedish kronor, about $1.2 million, according to NPR.