There is an increasing need for complex chemicals. Humanity wants new medicines that can cure cancer or halt the devastating effects of deadly viruses in the human body. The electronics industry is searching for substances that can emit light, and the agricultural industry wants substances that can protect crops. The Nobel Prize in Chemistry 2010 rewards a tool that has improved the ability of chemists to satisfy all of these wishes very efficiently: palladium-catalyzed cross coupling.
At the end of the 1980s, scuba divers in the Caribbean Sea collected the marine sponge Discodermia dissoluta. At a depth of 33 meters (108 feet) they found a little creature that lacks eyes, a mouth, stomach and bones. At first sight it appears primitive, but its inability to escape enemies has turned Discodermia dissoluta and other marine sponges into masters of chemistry. They have a remarkable ability to produce large and complex chemical molecules that are poisonous and that prevent other organisms from exploiting them.
Researchers have discovered that many of these poisons have therapeutic properties; they can function as antibiotics or as anti-viral or anti-inflammatory medicines. In the case of Discodermia dissoluta, the first laboratory tests revealed that the substance discodermolide could in the future be used as a chemotherapy drug. Among other things, it stopped cancer cells from growing in test tubes.
Removes a significant obstacle to progress After more in-depth studies, scientists have been able to demonstrate how discodermolide defeats cancer cells in the same manner as Taxol, one of the most commonly used cancer drugs in the world. Finding a substance with such huge potential is a thrilling experience in itself, but without the discoveries being rewarded by the Nobel Prize in Chemistry 2010, the story of discodermolide would probably have ended there (figure 1). Progress would have come to a halt due to a lack of material, as it is not possible to develop medicines based on a substance found only in small quantities deep in the Caribbean Sea. However, with the addition of palladium-catalyzed cross-coupling reactions to the chemist’s toolbox by Richard F. Heck, Ei-ichi Negishi and Akira Suzuki, scientists can now artificially produce discodermolide. Negishi’s variant of the reaction was used as a central step in its synthesis. Other scientists have subsequently optimized the process and managed to obtain sufficient quantities of discodermolide to begin clinical testing on humans suffering from cancer.
Removes a significant obstacle to progress After more in-depth studies, scientists have been able to demonstrate how discodermolide defeats cancer cells in the same manner as Taxol, one of the most commonly used cancer drugs in the world. Finding a substance with such huge potential is a thrilling experience in itself, but without the discoveries being rewarded by the Nobel Prize in Chemistry 2010, the story of discodermolide would probably have ended there (figure 1). Progress would have come to a halt due to a lack of material, as it is not possible to develop medicines based on a substance found only in small quantities deep in the Caribbean Sea. However, with the addition of palladium-catalyzed cross-coupling reactions to the chemist’s toolbox by Richard F. Heck, Ei-ichi Negishi and Akira Suzuki, scientists can now artificially produce discodermolide. Negishi’s variant of the reaction was used as a central step in its synthesis. Other scientists have subsequently optimized the process and managed to obtain sufficient quantities of discodermolide to begin clinical testing on humans suffering from cancer.
Only the future will tell if discodermolide turns out to be a life-saving drug. In any case, it is one of many examples of how naturally occurring chemicals inspire the work of chemists. Common to all molecules in living organisms, so called organic molecules, is the fact that they consist of a more or less complex skeleton of carbon atoms. Carbon-carbon bonds are the basis of the chemistry of life itself, and its importance to chemists is well illustrated by the fact that the subject matter has now been rewarded with a total of five Nobel Prizes. The previous four are: the Grignard reaction (1912), the Diels-Alder reaction (1950), the Wittig reaction (1979), and olefin metathesis (2005).
Palladium – point of rendezvous for carbon atoms
The palladium-catalyzed cross-coupling reaction is unique since it is possible to carry it out under mild conditions and with very high precision. Previously, chemists had to kick-start the chemical reaction between two carbon atoms using reactive substances. Such substances do their job, but the carbon often also reacts with other atoms leading to the creation of unwanted by-products.