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Two Americans and a Japanese were awarded this year's Nobel Prize in Chemistry for developing more efficient chemical reactions to produce many medicines, including L-dopa, the standard treatment for Parkinson's disease. Dr. William S. Knowles, 84, of St.
Louis, who retired from the Monsanto Company in 1986, and Dr. Ryoji Noyori, 63, director of the Research Center for Materials Science at Nagoya University in Japan, shared half of the $ 950, 000 award. Dr. K.
Barry Sharpless, 60, a professor of chemistry at the Scripps Research Institute in La Jolla, Calif. , received the other half. Dr. Eric N. Jacobsen, a professor of chemistry at Harvard University, said the winners' work "changed the field of chemistry. " The three scientists created catalysts that can selectively produce just one of two versions of a molecule, an essential requirement for the production of many drugs. Catalysts shepherd together other chemicals and increase the efficiency of reactions but remain unchanged themselves.
Dr. Knowles, a pioneer in the field in the late 1960 's, said he was overwhelmed by the honor because his work dates so far back. Most molecules come in two forms, identical in structure except that they are mirror images of each other, just as the left hand is the mirror image of the right. While they look alike, the two forms can have very different properties and sharply different effects on the body.
For example, one version of the molecule limonene smells of lemons; its mirror image smells of oranges. Sometimes the differences are catastrophic. In the drug thalidomide, one of the two forms eased nausea in pregnant women; the mirror image, which was not removed from the drug, caused limb deformities in thousands of infants born in Europe and Canada in the 1960 's. At that time, the chemical reactions used to manufacture drugs created equal amounts of the two mirror forms. The only way to produce a pure batch of one form was to separate it from the mirror image, a process that was difficult, costly and wasteful.
At least as far back as the 1950 's, chemists knew that some catalysts would produce more of one mirror image than the other, but the disparity was not large. "The principle was known, but it was not at all useful, " said Dr. Ernest L. Else, an emeritus professor of chemistry at the University of North Carolina. Dr.
Knowles, a senior chemist at Monsanto, decided to try to do better. He studied a catalyst that inserts two hydrogen atoms into a flat, two-dimensional molecule, between two carbon atoms. The addition causes the molecule to twist outward, and the direction of the twist determines which mirror form is created. Dr. Knowles modified the shape of the catalyst so that it could attach to only one side of the molecule, causing all the molecules to twist the same way and producing just one of the mirror forms. "Imagine a right-handed glove and it's trying to select between a right or left hand, " said Dr. Jacobsen of Harvard. "It's very much the same concept. "Dr.
Knowles then applied the technique to a project to produce the drug L-dopa, which counteracts symptoms of Parkinson's disease, like tremor and rigidity. The mirror form, D-dopa, is toxic. The reaction Dr. Knowles developed produced 97. 5 percent L-dopa and only 2. 5 percent of the unwanted D-dopa, and Monsanto used the process to make the drug commercially.
Dr. Noyori's contribution was to synthesize a better catalyst. In 1980, after six years of effort, he produced one that could insert hydrogen atoms into a wider range of molecules and produce even higher yields. The simple shape of the catalyst also appealed to chemists. "It's just a beautiful molecule, " Dr. Noyori said. The anti-inflammatory treatment naproxen is one drug produced using Dr.
Noyori's catalysts. About the same time, Dr. Sharpless produced similarly selective catalysts for a different type of reaction, which inserts oxygen atoms into a molecule. That was significant because chemists can attach other atoms to the oxygen atoms, leading to more complex products. Dr.
Amos B. Smith, a chemistry professor at the University of Pennsylvania, said Dr. Sharpless's research contributed "some of the most important reactions probably discovered in the last 50 years. " Those reactions have produced compounds like glycol, which is used to make beta-blocker heart medicines. This article discusses chemistry in the medical field.
When an antibiotic is produced, there is something called a mirror image of it. This mirror image is what causes most side effects. Some are more serious than others. For example, the drug thalidomide, one image eased nausea in pregnant women. However, the mirror causes limb deformities in infants.
Dr. Knowles has found a way to prevent the production of this mirror to a minimum. With this new technology, chemists and doctors may have found a way to do away with many horrible side effects. This is discussed in chapter 25.
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