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Life—and the large molecules that make it possible—relies on long chains of carbon, bonded together to form everything from carbohydrates to neurotransmitters. However, the process that occurs in say, in a leaf, in a series of carbon-to-carbon bonding steps known as the Calvin–Benson cycle, has proved difficult to emulate in the lab, because carbon does not seek on its own to bond with its fellow carbon. Now, the 2010 Nobel Prize in Chemistry has been awarded to three chemists who developed reactions that harness the catalytic properties of palladium to enable the formation of such carbon-to-carbon bonds at room temperature.
"I am interested in all organic molecules and being able to synthesize them in the best way possible," said new chemistry laureate Ei-ichi Negishi of Purdue University in a telephone call broadcast Wednesday at the press conference held in Stockholm, Sweden, to announce the award. "We believe that our chemistry will be applicable to a very wide range of compounds, without knowing what they might be."
Negishi, along with Richard Heck of the University of Delaware and Akira Suzuki of Hokkaido University in Japan, share the Nobel for developing chemical reactions that the scientists arrived at independently and that enable the building of complex organic compounds with wide application in medicine, industry and agriculture. The key to all three slightly different reactions is the element palladium, a relatively rare silvery-white metal that provides a setting that allows carbon atoms or compounds with carbon in them to bond to each other. In fact, the palladium bonds with the carbon atoms, drawing them together like a matchmaker. Once close enough, the carbons form their own attachment and drop the palladium, enabling the catalyst to produce more such pairings.
"What palladium does is to lower those energy barriers between atoms to make it easier for these reactions to occur," says chemist Joseph Francisco, president of the American Chemical Society. "Some reaction processes that required hundreds of degrees Celsius in order to make those reactions go can often be done with this at room temperature. You can imagine the energy savings of producing new materials."
Those materials range from carbon-based polymers such as styrene used to make plastics to organic compounds that can emit light, enabling thin television screens or computer monitors. The processes find their widest application, however, in synthesizing medicinal compounds, like Taxol, a cancer drug derived from the Pacific yew tree, or tumor-fighting discodermolide, a natural organic molecule isolated from a Caribbean sponge. "In this way, one could obtain the large quantities of discodermolide required" for further testing, explained Swedish organic chemist Jan-Erling Backvall, a member of the Nobel Committee for Chemistry, at the event announcing this year's prize.
In fact, efficiently forming carbon-to-carbon bonds has long been a focus of chemistry, and various methods—starting with Victor Grignard's use of magnesium to help bind carbon atoms in 1912—have been awarded the chemistry Nobel. "This won't be the last one," Francisco says. "What this does is add to the toolbox for a chemist in terms of tools that they can use to build [compounds] more cleanly and more efficiently."
Of course, all living things use similar chemistry to synthesize the compounds necessary for life. In the case of photosynthesis, an enzyme known as rubisco, helps knit the carbon bonds that store sunlight as chemical energy—and make the plant's food. But so-called palladium-catalyzed cross coupling chemistry enables scientists to manufacture organic compounds in the lab with fewer chemical steps than photosynthesis—building chains of carbon containing as many as 129 atoms. " This method has a high precision and avoids unwanted side reactions," said Swedish biochemist Lars Thelander, chair of the Nobel Committee for Chemistry, in announcing the award. "This allows the formation of compounds as complex as the one's found in nature."