Dr. Rosenkranz was one of numerous scientists and advocates whose work led to the widespread availability of “the pill,” a drug that has been used in various forms by hundreds of millions of women in the United States, where the first oral contraceptive was approved in 1960, and around the world.

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“The pill was not the result of serendipity,” Dr. Rosenkranz once said. “On the contrary, it was the result of a long chain of events, with many individuals and team players involved.”

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He conducted his research at Syntex, a pharmaceutical company based in Mexico City that he later led as chief executive and chairman. He had settled in Mexico after fleeing Europe along with other Jewish scientists during World War II; many of his relatives perished in the Holocaust.

From the earliest days of his career, Dr. Rosenkranz was fascinated by the possibility of making synthetic forms of naturally occurring hormones. In 1951, Syntex announced that scientists working under him had synthesized cortisone, a steroid hormone that reduces inflammation, using inedible yams found in Mexico. Earlier methods of making cortisone, which were vastly more laborious, required bile harvested from cattle.

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Later in 1951, Dr. Rosenkranz and two colleagues — Carl Djerassi, an Austrian-born scientist and fellow refugee from Nazi Europe, and Luis E. Miramontes, a Mexican doctoral student — were credited with making norethindrone, a synthetic version of the hormone progesterone that is also called norethisterone.

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Initially intended for a drug to prevent miscarriage, it later became the active ingredient in birth control pills. Dr. Rosenkranz credited Ludwig Haberlandt, an Austrian scientist, with identifying progesterone as a contraceptive in the 1920s.

“He asked a very simple question,” Dr. Rosenkranz told the Associated Press. “Why doesn’t a pregnant woman get pregnant again during her pregnancy? That is because of the role of the female hormone progesterone, which later as it turned out inhibits ovulation and all those number of processes.”

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In 1960, the Food and Drug Administration approved Enovid by the Searle pharmaceutical company, the first commercially available version of the pill. It was a watershed moment in the feminist movement as well as the culture wars — allowing women to enjoy sex without fear of becoming pregnant, permitting couples to decide when and whether to begin families, and setting off an enduring debate about sexual values.

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Similar drugs followed, including Syntex’s Norinyl in 1964, which helped turn the company into a juggernaut. When Dr. Rosenkranz joined Syntex, the company “was in shambles and nearly bankrupt,” he told the publication Pharmaceutical Executive. It was sold in 1994 for more than $5 billion to Roche Holdings.

Gyorgy Rosenkranz was born on Aug. 20, 1916, in Budapest, where his father ran a dance studio and his mother was a homemaker.

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He enjoyed an affluent, happy childhood in Hungary before moving to Zurich to attend the Swiss Federal Institute of Technology, where he studied under Leopold Ruzicka, who shared the 1939 Nobel Prize in chemistry. Dr. Rosenkranz received a chemical engineering degree in 1938 and a doctorate in technical sciences in 1940.

Amid the perils of World War II, Ruzicka obtained for Dr. Rosenkranz a professorship in Quito, Ecuador, according to Dr. Rosenkranz’s son. The Japanese attack on Pearl Harbor in 1941 — and subsequent entry of the United States into the war — cut short the journey, and Dr. Rosenkranz stopped in Havana.

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There he met and married Edith Stein, a Jewish refu­gee from Austria, in 1945. Dr. Rosenkranz found work at a Cuban pharmaceutical company where he used sarsaparilla root from Mexico to make small amounts of the hormones progesterone and testosterone. That work piqued interest at Syntex.

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Russell E. Marker, a scientist who had earlier worked for Syntex, had begun making progesterone from Mexican yam roots but had what Dr. Rosenkranz described as a “bitter falling-out” with the company and left.

When Dr. Rosenkranz arrived at Syntex, “there were no manuals, no process descriptions, and reagents and intermediates bore coded labels,” he recalled in a Syntex alumni publication. “As chemical archaeology was not my area of expertise, I started from square one, developing my own processes. Soon we were back in production.”

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Other innovations under Dr. Rosenkranz included the manufacture of Naproxen, a nonsteroidal anti-inflammatory drug used for arthritis and other conditions.

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Dr. Rosenkranz became a Mexican citizen in 1949 and a U.S. citizen when he was in his 90s. Besides Roberto Rosenkranz, of Atherton, Dr. Rosenkranz’s survivors include his wife, also of Atherton; another son, Ricardo Rosenkranz of Chicago; and nine grandchildren. His son Gerardo Rosenkranz died in 2011.

An accomplished bridge player, Dr. Rosenkranz wrote more than a dozen books about the card game and was inducted in 2000 into the Hall of Fame of the American Contract Bridge League, which named him a Grand Life Master.

He and his wife were competing in a bridge competition in Washington in 1984 when Edith Rosenkranz was kidnapped at gunpoint at a hotel garage and held for nearly two days for a $1 million ransom. Her abductors released her near the Mall after receiving the ransom, which Dr. Rosenkranz, under the guidance of law enforcement authorities, deposited under a car in a parking lot in Alexandria, Va.

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Three men — Glenn Wright, who was a fellow bridge player, and Dennis Moss and Orland Tolden — were arrested in connection with the crime and sentenced to prison.

Speaking with his mother after her release, Ricardo Rosenkranz remarked on how terrible the ordeal must have been for her. She replied that compared with living through the Holocaust, it had been easy — a demonstration of the “mettle” that he attributed to his parents.

“I leave to others any debate about the ultimate worth of the pill,” Dr. Rosenkranz said when he was honored at the University of Mexico in 2001 for his scientific achievements. “We must never forget that original research is the lifeblood of the pharmaceutical and biotechnology industry [and] that an interdisciplinary team effort is the indispensable motor of significant research achievement.”