Diels, Otto Paul Hermann (1876-1954)

German chemist. He and his former assistant, Kurt Alder, were awarded the Nobel Prize for Chemistry in 1950 for their research into the synthesis of organic compounds.

In 1927 Diels dehydrogenated cholesterol to produce ‘Diels hydrocarbon’ (C18H16), an aromatic hydrocarbon closely related to the skeletal structure of all steroids, of which cholesterol is one. In 1935 he synthesized it. This work proved to be a turning point in the understanding of the chemistry of cholesterol and other steroids.

Diels was born in Hamburg and studied at Berlin. He was director of the Chemical Institute at the Christian Albrecht University in Kiel 1916-48.

Working with his assistant Alder, Diels developed the diene synthesis, which first achieved success in 1928, when they combined cyclopentadiene with maleic anhydride (cis-butenedioic anhydride) to form a complex derivative of phthalic anhydride. Generally, conjugated dienes (compounds with two double bonds separated by a single bond) react with dienophiles (compounds with one double bond activated by a neighbouring substituent such as a carbonyl or carboxyl group) to form a six-membered ring.

Diels published a textbook, Einführung in die organische Chemie/Introduction to Organic Chemistry (1907).