Austrian-born U.S. chemist Carl Djerassi, known for the development of the first oral contraceptive pill, in 2008. (Heinz-Peter Bader/Reuters)

Carl Djerassi, who provided the chemistry behind the sexual revolution by patenting the synthetic hormone used in the Pill, the oral contraceptive sold under various names in the U.S. since 1960, died Jan. 30 at his home in San Francisco. He was 91.

The cause was complications of liver and bone cancer, said his son, Dale.

An Austrian-born research chemist, Dr. Djerassi crossed academic disciplines to study how the birth-control pill he helped create influenced women’s health, gender equality and global population.

“By separating the coital act from contraception, the Pill started one of the most monumental movements in recent times, the gradual divorce of sex from reproduction,” he wrote in “This Man’s Pill: Reflections on the 50th Birthday of the Pill” (2001), the last of three autobiographies.

As a professor at Stanford University, he explored the human side of science and the moral conflicts scientists face in novels, nonfiction books, plays and short stories.

He took issue with the oft-repeated title “father of the Pill,” saying it excluded others such as biologist Gregory Pincus and obstetrician-gynecologist John Rock, who played key roles in the decades-long path toward an oral contraceptive.

In 1951, as associate director of chemical research at Syntex SA in Mexico City, Dr. Djerassi led work on a synthetic version of progesterone, a hormone secreted by the female reproductive system.

Using diosgenin, a chemical abundant in Mexican yams, the Syntex team created a contraceptive steroid that could be taken orally. The drug, called norethindrone, was successfully synthesized on Oct. 15, 1951, and patented by Dr. Djerassi along with Syntex colleagues George Rosenkranz, the chief chemist who would rise to chairman, and Luis Miramontes, a doctoral student in their lab.

The birth-control pill first approved by the U.S. Food and Drug Administration -- Enovid, in 1960 -- was developed not by Dr. Djerassi but by a competitor, Frank Colton at G.D. Searle. In short order, though, Dr. Djerassi’s version was also approved and became an industry standard. Syntex then introduced its own pill, called Norinyl.

By 1965, seven U.S. companies were marketing versions of the Pill, with sales reaching $65 million, according to Time magazine. Syntex — incorporated in Panama and operating largely in Mexico -- was then the most heavily traded company on the American Stock Exchange, supplying the basic compound for its own version and for those made by Eli Lilly, Johnson & Johnson, and Parke, Davis, now a unit of New York-based Pfizer.

Syntex was acquired in 1994 by Basel, Switzerland-based Roche, the world’s biggest maker of cancer drugs.

Starting with a 1969 piece for Science magazine on global implications of U.S. contraceptive research, Dr. Djerassi waded into the public-policy debate spawned in part by his creation.

Hippie culture, rock-and-roll and women’s liberation would have triggered a sexual revolution even if the birth-control pill didn’t exist, he said. One sure effect of the Pill, he said, was fewer unwanted pregnancies and abortions.

“No one expected that women would accept oral contraceptives in the manner in which they did in the ‘60s,” Dr. Djerassi told the London Guardian in 2007. “The explosion was much faster than anyone expected.”

A few years later, according to the Guardian, Dr. Djerassi cited one way in which the Pill worked against the best interests of women.

“Modern, intelligent men won’t take responsibility, wouldn’t even use condoms,” he said. “They shrugged and said: ‘All women are now on the pill, I don’t need to bother.’ This has become another woman’s burden.”

His role in creating the contraceptive, he wrote in his 2003 autobiography, turned him “from a ‘hard’ physical scientist to a much ‘softer’ chemist concerned with the deeper social ramifications of my work.”

Carl Djerassi was born on Oct. 29, 1923, in Vienna to two Jewish doctors: Bulgarian-born Samuel Djerassi, who specialized in venereal diseases, and the former Alice Friedmann, a Viennese dentist. They divorced when he was young.

Fleeing the Nazis in the late 1930s, Dr. Djerassi and his mother emigrated to the United States, settling in New York City with little money. He graduated from Kenyon College in Gambier, Ohio, with a degree in organic chemistry in 1942.

While working as a research chemist at Ciba Pharmaceutical Co. in Summit, N.J., he began his graduate studies at Polytechnic Institute of Brooklyn, today’s Polytechnic Institute of New York University. In 1945, he received a Ph.D. from the University of Wisconsin in Madison.

Dr. Djerassi spent four more years with Ciba, researching steroids, before joining Syntex in Mexico City, where, in addition to norethindrone, he worked on synthesizing cortisone.

He returned to the United States in 1952 to teach at Wayne State University in Detroit while continuing his association with Syntex. From 1959 to 2002, he was a professor at Stanford, where he designed an undergraduate course called “Biosocial Aspects of Birth Control” and a graduate writing course on biomedical ethics.

He won the National Medal of Science in 1973, for his work on the Pill, and the National Medal of Technology in 1991, for his leadership at Zoecon, a developer of environmentally friendly insect control products. He was inducted into the Inventors Hall of Fame in 1978 for research that led to antihistamines and anti-inflammatory drugs in addition to oral contraceptives.

Perhaps fittingly for a man associated with the sexual revolution, Dr. Djerassi was open about his own turbulent romantic history.

While married to his first wife, the former Virginia Jeremiah, he had an affair that resulted in the pregnancy of the woman who would become his second wife, Norma Lundholm. (He later acknowledged it was “ironic” that he of all people had contributed to an accidental pregnancy, which he attributed to failure of a condom. He had a vasectomy in his 50s.)

That pregnancy produced a daughter, Pamela Djerassi Bush, an artist who committed suicide in 1978, at 28. In her honor, her parents founded the Djerassi Resident Artists Program, an artists’ retreat near Woodside, Calif.

Dale Djerassi, his son by his second wife, is a filmmaker. That marriage, like his first, ended in divorce. Dr. Djerassi’s survivors also include a grandson and a stepdaughter, Leah Middlebrook, according to the Times.

His third wife, Diane Middlebrook, a biographer and English professor at Stanford, died in 2007.

— Bloomberg News