Karrer, Paul (1889–1971)

Russian-born Swiss organic chemist who shared the Nobel Prize for Chemistry in 1937 for his work in carotenoids, flavins retinal (vitamin A) and riboflavin (vitamin B2), and determining their structural formulae.

Karrer was born in Moscow but grew up in Switzerland. He studied at Zürich, was professor at the Zürich Chemical Institute from 1918 and its director 1919–59.

Karrer's early work concerned vitamin A and its chief precursor, carotene. Karrer worked out its correct constitutional formula in 1930, although he was not to achieve a total synthesis until 1950. He showed in 1931 that vitamin A is related to the carotenoids, substances that give a yellow, orange, or red colour to many foodstuffs. There are in fact two A vitamins. Karrer proved that there are several isomers of carotene, and that vitamin A1 is equivalent to half a molecule of its precursor β-carotene.

In 1935, he synthesized vitamin B2 (riboflavin). He also investigated vitamin E (tocopherol), which is a group of closely related compounds, and in 1938 he solved the structure of α-tocopherol, the most biologically active component.

In 1927, Karrer published Lehrbuch der organischen Chemie/Textbook of Organic Chemistry.