How was Leopold Ružička awarded the Noble Prize?

Leopold Ruika was a Croatian-Swiss scientist who won the 1939 Nobel Prize in Chemistry for his work on polymethylenes and higher terpenes, including the first chemical synthesis of male sex hormones.
Ruzicka synthesized androsterone and testosterone in 1934, leading to the preeminence of the Swiss industry in the steroid hormone field. He became a professor of organic chemistry at ETH in Zurich and widened his research to include higher terpenes and steroids. After the successful synthesis in 1935 of sex hormones (androsterone and testosterone), his laboratory became the world center of organic chemistry, and he was awarded an honorary degree from Harvard University in 1936.