Eugene van Tamelen, 84, a Stanford University chemist who was a pioneer in determining the structure of complex natural molecules and then synthesizing them, died Dec. 12 of cancer, the university announced.

He was "an exceptional intellect, with an extraordinary imagination," said chemist John Brauman, now a professor emeritus at Stanford. "He was constantly inventing new reactions and new approaches to interesting molecules."

Dr. van Tamelen liked being different and he liked being first, colleagues said, and the problems he worked on had to be big ones, typically involving molecules much more complex than anyone had been able to make before.

While he was a graduate student at Harvard University working in the laboratory of chemist Gilbert Stork, Dr. van Tamelen played a key role in the total synthesis of cantharidin, the central ingredient of the notorious aphrodisiac Spanish Fly. That work is considered the first synthesis of a complex natural product in which the correct three-dimensional configuration of each atom was achieved.

He was named one of the 2,000 best scientists of the 20th century by the International Biographical Centre of Cambridge, England, and received virtually all of the top awards presented by the American Chemical Society.

He was born in Zeeland, Mich. His forebears were woodworkers, and he frequently said that he got his gift for spatial thinking - crucial in synthesizing natural products - from them.

He graduated from Hope College in 1947 and received his doctorate from Harvard University in 1950. He joined the faculty of the University of Wisconsin and stayed until he went to Stanford in 1962, spending the rest of his career there.

- Los Angeles Times