Two Americans and a French scientist shared the Nobel Prize in Chemistry yesterday for discoveries that make it possible to create synthetic substances more easily, cheaply and cleanly for a host of purposes, including drugs, plastics and chemicals used in everyday life.

Robert H. Grubbs, 63, of the California Institute of Technology in Pasadena, Richard R. Schrock, 60, of the Massachusetts Institute of Technology in Cambridge and Yves Chauvin, 74, of the French Petroleum Institute in Rueil-Malmaison, France, will share the $1.3 million award from the Royal Swedish Academy of Sciences.

Chauvin figured out in 1971 how a key chemical process known as metathesis works and what types of metal compounds act as catalysts for the reaction, providing a crucial "recipe" for making it practical, the Nobel committee said. In 1990, Schrock produced the first efficient metal catalyst for the process. Two years later, Grubbs developed "an even better catalyst, stable in air, that has found many applications," the committee said.

Metathesis, which means to "change places," has been likened to a "change-your-places" square dance in which double bonds between carbon atoms are broken and then reformed, allowing different components to swap positions like dancers moving around a dance floor, creating new materials. During the awards announcement yesterday, two men from the Nobel committee moved to the floor of the wood-paneled academy hall to dance with two women, exchanging partners to illustrate how the process works.

"Metathesis is an example of how important basic science has been applied for the benefit of man, society and the environment," the committee said.

The process has myriad applications and has been employed in a wide array of commercial uses by the pharmaceutical, biotechnology, agricultural and plastics industries to produce drugs, advanced plastics, herbicides, fuel additives and other substances.

"The achievements of the laureates have given us fantastic opportunities for producing new molecules," said Academy Secretary General Gunnar Oequist in making the announcement in Stockholm.

Because building molecules is "the soul of chemistry," the work will probably yield a host of new substances, said Astrid Graeslund, Nobel committee secretary.

"The beauty of this is that it's a reaction that you can now guide very precisely what will happen, exactly as you would like," she said.

The process can be easily controlled and involves fewer steps, making it less cumbersome and less expensive, and producing far less waste, making it more environmentally friendly, she said.

"If you were going to do this kind of reaction in the old way, it would involve many, many steps. . . . In every reaction, you make waste products that you have to discard," she said. "With this you can make a shortcut. You can make a reaction that causes very little waste and make only the product you want."

Researchers have recently begun using the process to try to develop new medications for diseases including hepatitis C, cancer, Alzheimer's disease, arthritis and AIDS, the academy said.

"Metathesis is thus an important weapon in the hunt for new pharmaceuticals for treating many of the world's major diseases," the committee said.

The recipients all said they were surprised and honored.

"It's one of the things one never expects to happen," Grubbs said from a hotel room in Christchurch, New Zealand, where he received word while on a lecture tour. "One hears rumors but never expects it."

"It's obviously a tremendous honor," Schrock said at a news conference at MIT. "So now I know -- dreams can come true."

Schrock said the prize shows the importance of basic research.

"I got here by doing basic research, and doing basic research these days doesn't have a lot of cachet to it," Schrock said. "But basic research is still very, very important."

In Tours, France, Chauvin said he felt "embarrassment, not joy," and told reporters that "I had a quiet life; now I see that that is no longer the case," the Associated Press reported.

"I knew that my research was important. I opened the way, but it is my American colleagues who also worked on my research who are enabling me to get this prize today," Chauvin said. "It took 30 years of laboratory work to show that what I found was interesting."

Massachusetts Institute of Technology's Richard R. Schrock.California Institute of Technology professor Robert H. Grubbs.

French chemist Yves Chauvin in Tours, France.