A childhood in hiding
Henri Boris Kagan was born on December 15, 1930, in Boulogne-Billancourt, on the western edge of Paris, into a Jewish family. He was eight when the Second World War began. After Germany occupied France in 1940 and the Vichy regime and the Nazis began rounding up Jews for deportation, the Kagan family escaped persecution by hiding in a village in southern France under assumed names. They survived. Around 75,000 Jews were deported from France during the war, and the great majority did not return.
In October 2026, when he became a Nobel laureate at the age of 95, Jewish organisations and newspapers described him as a Holocaust survivor. Few details of those years have been published, and he built his life in the country that once hunted his family, becoming one of its most honoured scientists.
Training as a chemist
After the war Kagan studied at the Sorbonne and at the École nationale supérieure de chimie de Paris, now Chimie ParisTech, graduating as a chemical engineer in 1954. He went on to doctoral research at the Collège de France under the chemist Jean Jacques, working on the chemistry and three-dimensional shape of steroids, the family of molecules that includes many hormones and medicines. He received his doctorate in 1960 and then worked as a research associate with Alain Horeau, who held the Collège de France chair of the organic chemistry of hormones and was a specialist in molecular handedness.
In the late 1960s Kagan set up his own research group at the Faculty of Science in Orsay, south of Paris, part of what became the Université Paris-Sud and later the Université Paris-Saclay. He spent the rest of his career there, becoming professor emeritus in 1999 and continuing to lecture, write and mentor long afterwards. At Orsay his group worked across the whole of asymmetric synthesis, from new catalysts to new reagents.
Left hand, right hand
Many molecules, like hands, come in two mirror-image forms that cannot be superimposed on each other. Chemists call them enantiomers. Life is strikingly one-handed: the amino acids in our proteins are all of one form, and the sugars in our DNA are all of the other. This matters enormously for medicine. A drug molecule usually works by fitting into a protein in the body like a key into a lock, and only one of its two mirror images fits properly. The other may do nothing, or may cause harm. The Nobel committee recalled the thalidomide disaster of the early 1960s, in which thousands of children were born with birth defects, as the event that showed how important it is to make the right mirror image.
The puzzle is an old one. In 1848 Louis Pasteur, examining crystals of tartaric acid from wine-making, separated them by hand with tweezers into two mirror-image forms that bent polarised light in opposite directions. In 1857 he found that bacteria would ferment one form but not the other, the first sign that life’s chemistry is one-handed. In 1953 the British physicist Charles Frank proposed, purely on paper, the conditions under which a chemical reaction could make one hand win out completely: a one-handed catalyst, a way of favouring one form over the other, and a product that catalyses its own formation. For decades this remained a puzzle that lecturers set their students. Kagan and Soai would eventually supply the missing pieces in the laboratory.
Yet when chemists make such molecules in the laboratory, they normally get an equal mixture of both. Separating them is wasteful and expensive. The solution is asymmetric synthesis: using a catalyst that is itself one-handed to steer a reaction toward a single form.
Tools for one-handed chemistry
Kagan was one of the founders of this field. In 1971 he introduced a catalyst ingredient called DIOP, a molecule with a special two-fold symmetry that binds to a metal atom and makes the metal favour one mirror-image product. It was one of the first highly effective ligands for asymmetric catalysis, and its design principle inspired many related catalysts that followed. The Wolf Foundation honoured him in 2001, together with Ryoji Noyori and K. Barry Sharpless, for this pioneering work.
In 1984 Kagan’s group, and independently Giorgio Modena’s group in Italy, showed how to adapt a titanium and tartrate catalyst so that it could add an oxygen atom to sulphur-containing molecules and produce one mirror image of the product. Versions of this Kagan oxidation were applied to the manufacture of esomeprazole, the single mirror-image form of the acid-reflux and ulcer drug omeprazole, a widely used medicine. In 1979 and 1980 his laboratory also showed that samarium diiodide, sometimes called Kagan’s reagent, can transform many kinds of organic molecules under unusually mild conditions. Because it is gentle and selective, able for example to act on one part of a molecule while leaving sensitive groups elsewhere untouched, it became a standard tool for chemists building complex molecules, from natural products to drug candidates.
The non-linear effect
In the early 1980s chemists assumed that if a catalyst was only partly pure, containing some of both mirror images, the product would be exactly as impure. The relationship was thought to be a straight line. Kagan questioned this. He reasoned that a metal atom in a catalyst often holds two of the one-handed molecules at once, so a mixture would produce three kinds of catalyst: right-right, left-left and left-right. If the mixed left-right form behaved differently, the straight line might bend. As the Nobel committee described it, while many chemists were busy refining asymmetric reactions to get purer products, Kagan took the time to think about the catalyst itself, and how its metal atom and one-handed molecules actually interact, something nobody then understood.
In 1986, in the Journal of the American Chemical Society, he reported three different reactions in which it did. The left-right catalysts worked far more slowly, so the pure catalysts dominated, and the product came out purer than the catalyst that made it. He called this a non-linear effect and developed mathematical models to explain it. The discovery gave chemists a powerful new way to analyse how catalysts work and to get highly pure products even from imperfect starting materials. It also inspired the Japanese chemist Kenso Soai, who in 1995 designed a reaction in which the product catalyses its own formation, and by 2003 had shown that a tiny excess of one mirror image could be amplified until essentially only that form remained. Together the two discoveries offered a chemical explanation of how life could have become one-handed.
The Nobel Prize
On October 7, 2026, the Royal Swedish Academy of Sciences awarded the Nobel Prize in Chemistry to Henri Kagan and Kenso Soai for the discovery of non-linear effects and autocatalysis in asymmetric organic synthesis. The chair of the Nobel committee, Heiner Linke, said they had solved a chemical mystery more than a century old: how homochirality can emerge spontaneously. The Academy said their discoveries have been decisive for chemists who design reactions for the manufacture of pharmaceuticals, and described Kagan’s discovery as revolutionary for those who develop reactions to make medicines, flavours, scents and new materials. Each laureate received half of the prize of 12 million Swedish kronor.
Many chemists had expected Kagan to share the 2001 prize for asymmetric catalysis, which went to William Knowles, Ryoji Noyori and Sharpless; French officials protested at the time, but the prize is limited to three people. Twenty-five years later, at 95, he was recognised in his own right. President Emmanuel Macron called the award an immense source of pride for France and a recognition befitting a lifetime of research.
Honours and influence
Before the Nobel Prize, Kagan had received many of chemistry’s highest awards, among them the Tetrahedron Prize, the Wolf Prize in Chemistry, the Ryoji Noyori Prize and the Franklin Institute’s Bower Award, whose citation credited him with greatly simplifying the manufacture of pharmaceutically important compounds. He is a member of the French Academy of Sciences, a Knight of the Legion of Honour and a recipient of honorary doctorates. For decades after his retirement he remained active as a visiting lecturer, author and mentor,.
Jewish identity
Kagan’s Jewish origins shaped his earliest years. As a boy he lived under a false name, part of the generation of Jewish children in France who survived the Holocaust because their families went into hiding. Reports of his Nobel Prize in the Jewish press, citing the World Jewish Congress, highlighted that he is a Holocaust survivor. He has kept his private life largely out of public view, and little has been published about his parents or his later religious life. The Jewish Virtual Library describes him as a French Jewish chemist.
Legacy
Kagan helped give chemists control over one of nature’s subtlest properties, the handedness of molecules. His catalysts and reagents are part of the standard toolkit of synthetic chemistry, his oxidation method helped make a single-mirror-image version of a medicine taken by millions, and his non-linear effect changed how chemists think about catalysts and about the origin of life’s one-handed chemistry. For a child who survived the war under an assumed name, it is a lifetime of work that has made medicines purer, safer and easier to produce for people everywhere.
Sources & further reading
Press release: The Nobel Prize in Chemistry 2026, NobelPrize.org · Popular information: The Nobel Prize in Chemistry 2026, NobelPrize.org · French Holocaust survivor wins 2026 Nobel Prize in Chemistry, The Algemeiner · Henri Kagan, Jewish Virtual Library · US Patent 8889873, Process for the preparation of enantiomerically enriched proton pump inhibitors, Google Patents · Henri B. Kagan, Wikipedia · Researched from the sources above and checked against them. Spotted an error? Tell us.
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