Why in the News
Chemists have moved from making mirror-image molecules as near-even mixtures of both forms to producing one form almost exclusively, as living cells do. The 2026 Nobel Prize in Chemistry has gone to Henri B Kagan of France and Kenso Soai of Japan “for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis“.
What is chirality, and why does life use only one form?
- What it is: Some molecules exist in two forms that are mirror images but cannot be superimposed, like a person’s left and right hands. This property is called chirality.
- Enantiomers: The two forms, called enantiomers, have the same atoms joined in the same order. Only their three-dimensional arrangement differs.
- Homochirality: Life’s building blocks, such as the amino acids in proteins and the sugars in DNA, use only one form. This preference is called homochirality.
- Laboratory problem: Ordinary chemical reactions produce both enantiomers in almost equal amounts, so chemists had to separate the form they wanted.
- The takeaway: Making only the form the body uses lets chemists copy what living cells do, which is why the work matters for medicines.
How did Kagan and Soai make one form dominate?
- Marckwald’s start: In the early 1900s, German chemist Willy Marckwald used a chiral catalyst (a chemical that speeds a reaction without being used up) and got slightly more of one form.
- Stalled progress: Later attempts failed to raise this asymmetry, and chemists did not understand how a chiral catalyst skewed the result.
- Kagan’s non-linear effect: Chemists assumed a linear relationship: a product favours one form only as much as its catalyst. In the 1980s, Kagan showed a catalyst barely favouring one form could yield a product strongly favouring it.
- Soai’s autocatalysis: In an autocatalytic reaction, the product itself acts as the catalyst. From the 1990s, Soai spent about a decade building one in which a single enantiomer copied itself.
- Near-total selectivity: Soai’s final product held 99.5% of one enantiomer, close to the preference seen in living systems.
Why does it matter beyond the laboratory?
- Medicines: Many drug molecules are chiral, and the human body uses only one form. The other form can be ineffective or even harmful.
- Cleaner manufacture: Drug makers once produced both forms and then separated the useful one, an expensive and wasteful process. Asymmetric synthesis now makes the needed form directly and is widely used.
- Wider uses: The same approach serves other products that interact with living organisms, such as flavours, fragrances and pesticides.
- Origin of life: The work shows homochirality can arise in a laboratory, not only in nature. It does not explain how life itself came to prefer one form.
What does the thalidomide tragedy show?
- Morning sickness drug: Thalidomide, a sedative marketed by a West German company from the late 1950s, was widely prescribed, including to pregnant women for morning sickness.
- Birth defects: By 1961, doctors had linked it to severe birth defects in thousands of babies across 46 countries, many with phocomelia (severely shortened or absent limbs).
- Mirror-image problem: One enantiomer produced the desired effect and the other caused the defects. The two forms were later found to interconvert in the body.
Challenges
- Conversion inside the body: Some drugs switch between forms after they are taken, so a pure enantiomer alone cannot guarantee safety. Eg. Thalidomide.
- Narrow reactions: Autocatalytic reactions like Soai’s work only for specific molecules, so extending them to many industrial products is difficult.
- Testing burden: Each enantiomer of a new drug must be studied separately for its effects, which raises development time and cost.
- Unsolved origin: The work shows how one form can come to dominate, but not why life settled on the forms it uses.
Way Forward
- Enantiomer-level safety review: Drug regulators should require data on both forms of a chiral drug, and on their interconversion, before approval.
- Greener generic manufacture: Indian drug makers can use asymmetric catalysis to cut waste and cost in producing active ingredients.
- Origin-of-life research: Fund research linking autocatalysis to how homochirality first emerged on the early Earth.
Conclusion
Chemists can now make the one mirror-image form that living systems use, a capability that medicine and agriculture already rely on. Why life chose one form in the first place remains unanswered, and that is where this work points next.
Matching Previous Year Question
“[2026] ‘X’, born in the UK, was conferred the Nobel Prize in 2025. He was a professor in an American university when the prize was announced. Identify ‘X’: (a) Michel H. Devoret (b) Richard Robson (c) John Clarke (d) Joel Mokyr ANSWER: C”
