John C. Sheehan, who in 1957 chemically synthesized penicillin, a feat that had been thought impossible, died March 21 of congestive heart failure at his home in Key Biscayne, Fla. He was 76 years old.
Sheehan, a professor of organic chemistry, emeritus, at the Massachusetts Institute of Technology, taught at that school for 31 years. He joined the faculty there as an assistant professor in 1946 and in 1948 began working on the synthesis of penicillin. The formation of a just small amount of natural penicillin from mold took months, which proved inefficient during World War II, when demand for the antibiotic escalated.
Sheehan worked for nine years on penicillin synthesis. His work made possible the creation of different, bacteria- specific penicillin drugs. Eventually, improvements in fermentation technology made possible the commercial production of penicillin.
Sheehan was the discoverer of ampicillin, a semisynthetic penicillin taken orally. His research also focused on amino acids, peptides, alkaloids, and steroids.
At MIT, Sheehan was promoted to associate professor in 1949 and to full professor in 1952, and became professor emeritus and senior lecturer in 1977. He was the author of The Enchanted Ring: The Untold Story of Penicillin, published by MIT Press in 1982.
Sheehan received his Ph.D. in 1941 from the University of Michigan. From 1941 to 1946, he was a senior research chemist at Merck & Co. of Rahway, N.J.
He received the John Scott Award for inventions benefiting humankind from the city of Philadelphia in 1964. He was a scientific adviser to Presidents John F. Kennedy and Lyndon B. Johnson from 1961 through 1965. He was a member of the National Academy of Sciences.