Henri Kagan at the University Paris-Saclay in France and Kenso Soai at the Tokyo University of Science in Japan have won the 2026 Nobel prize in chemistry for their work developing organic reactions that catalyse themselves and lead to an excess of one enantiomer over the other. These autocatalytic reactions also shed light on one of chemistry’s greatest mysteries – how life came to favour molecules with a certain handedness.
Life only functions with molecules that have a specific handedness, or chirality, including amino acids, sugars and DNA. This property is also crucial for organic chemists synthesising drug molecules, for example, as one form can have a desired therapeutic effect, while the other may lead to harmful side effects.
Yet, the puzzle of how life’s chemistry came to be one-handed is something that chemists have been pondering over for many years. In 1953, Charles Frank – a theoretical physicist from the University of Bristol – proposed a mathematical model for a chemical reaction that would result in a homochiral solution that contained just one enantiomer. He said that the reaction must use a chiral catalyst and the formation of one enantiomer must be favoured over the other, known as an asymmetric reaction. Equally, he said that any mirror-image molecule produced should form its own catalyst, autocatalysing its own synthesis.
However, fulfilling the last of Frank’s conditions was more challenging. This year’s Nobel prize recognises the work by Kagan and Soai, who have developed reactions that tick these boxes.
In the early 1980s, Kagan combined an unequal mixture of both left- and right-handed versions of a molecule along with a metal catalyst. He found that varying the ratio of enantiomers led to a different proportion of enantiomeric products, which followed a non-linear relationship. He concluded that some of the combinations of catalysts with some of the enantiomers were more effective than others, enhancing the formation of one enantiomeric product over another.
Building on Kagan’s work, Soai started searching for non-linear, asymmetric reactions that could catalyse their own formation. And in 2003, Soai succeeded. He showed that reacting a chiral aldehyde-containing pyrimidine with an alkyl zinc reagent, along with a chiral alcohol catalyst (the desired product of the reaction), produced the alcohol with same configuration as the catalyst. By starting with a reaction mixture with a small excess of one enantiomer, he eventually produced a solution containing more than 99.75% of one enantiomer. This reaction now bears his name and completes Frank’s conditions.
Peter Somfai at Lund University, Sweden, who is a member of the Nobel Committee for Chemistry, said at the announcement of the prize that the Soai reaction ‘is probably the coolest experiment in organic chemistry’.
The work of Kagan and Soai work offers scientists one way to understand how life’s homochirality could have originated from a racemic mixture of chiral compounds. However, exactly what occurred when life’s homochirality first arose is unlikely to be ever known.
Robert Mokaya, president of the Royal Society of Chemistry, notes that ‘different isomers can have completely different biological and physical effects, so are crucial in finding effective medicines to treat all sorts of illnesses’. ‘I add my congratulations to Henri Kagan and Kenso Soai on this hugely deserved honour from the Nobel prize committee.’
Kagan and Soai will share the prize of 12 million Swedish kronor (£906,000) that was awarded by the Royal Swedish Academy of Sciences.
This is not the first time that asymmetric catalysts have been recognised with a Nobel prize. For example, William S Knowles, Ryoji Noyori and Barry Sharpless developed reactions catalysed by chiral transition metal catalysts, which won them the 2001 Nobel prize in chemistry. At that time there was anger in some quarters in France that Kagan had been excluded from that prize. Two decades later, the chemistry Nobel committee awarded Benjamin List and David MacMillan the prize for their work developing asymmetric reactions catalysed by small, organic molecules.
No comments yet