(b. Moscow, Russia, 21 April 1889; d. Zurich, Switzerland, 18 June 1971)
Karrer was the son of Paul Karrer, a Swiss dentist who practiced in Russia, and Julie Lerch Karrer. In 1892 the family returned to Switzerland, where Karrer was educated in the cantonal schools of Aargau. In 1908 he entered the University of Zurich and studied chemistry with Alfred Werner, whose lecture assistant he became. He began an independent study of organic arsenic compounds, and because of his interest in this field he went to Frankfurt in 1912 to work with Ehrlich.In 1914 Karrer married Helene Froelich, daughter of a director of a psychiatric clinic; they had three sons, one of whom died in childhood. The following year, after Ehrlich’s death, Karrer became director of the chemical division of Georg Speyer Haus. In 1918 he accepted a call to the University of Zurich, where he succeeded Werner as professor of chemistry in 1919. In spite of many offers from other institutions, Karrer remained at Zurich for the rest of his life, serving as rector of the university from 1950 to 1952.
Karrer was a versatile organic chemist. The large number of students whom he attracked and the wide variety of problems that he attacked are attested by the more than 200 dissertations he directed, his more than 1,000 publications of all types, and his successful Lehrbuch der organischen Chemie (1928), which went through fourteen editions and was translated into seven languages.
When Karrer returned to Zurich, by undertaking study of the structures of amino acids, peptides, and proteins, he demonstrated that all these compounds had the same steric configuration. At the same time he studied a number of highly polymerized carbohydrates such as starch and cellulose. During the 1920’s his attention was drawn to the pigments of plants, and he began the study of natural products, which occupied most of his career. After studying anthocyanin pigments, he turned his attention to the study of the carotenoids, a branch of organic chemistry with which his name is closely associated. By 1930 he had solved the longpuzzling problem of the structures of carotene and lycopene. During this work he did much to revive the almost forgotten contribution of Tsvet to chromatography; this not only made possible the isolation of a number of new carotenoids, but in its later developments became an important tool for many branches of chemistry.
The work on carotene led him to investigate the question of the nature of vitamin A, the configuration of which–closely resembling that of a part of the carotene molecule–he recognized in 1931. He was able to establish its structure before the pure substance had been isolated. He then studied other fat-soluble vitamins, which in part resembled vitamin A. In 1938 he established the formulas for and β-tocopherol (vitamin E), and in 1939 he isolated vitamin K. During the same decade he investigated the flavonoids, a class of yellow pigments. In 1935 he synthesized one of the most important of the flavins, riboflavin (vitamin B2), and in addition investigated the chemistry of vitamin C and another B vitamin, biotin. In 1937 he received the Nobel Prize for his chemistry “researches into the constitution of the carotenoids, flavonoids, and vitamins A and B.” He shared the award with Walter N. Haworth, who had worked on the constitution of carbohydrates and vitamin C.
In 1942 Karrer contributed greatly to an understanding of the structure and function of nicotin-amide-adenine dinucleotide (NAD), a coenzyme essential for the transfer of electrons in the energy system of the cell. In 1950 he accomplished the total synthesis of carotenoids. At the beginning of his carreer he had worked for a time on alkaloids, and after 1945 he resumed these studies, determining the structures of certain curare-like alkaloids. Karrer was honorary member of several scientific societies, from many of which he received medals. Reserved and retiring, Karrer led a quiet life in his home and garden on the Zurichberg. He refused to own an automobile, and upon his retirement in 1959 he burned most of his scientific correspondence.
In addition to Lehrbuch der organischen Chemie (14th ed., Stuttgart, 1963), Karrer summarized his work on carotenoids in Carotinoide (Basel, 1948), written with E. Jucker. His biography, including references to his most important papers, is A.Wettstein, “Paul karrer,” in Helvetica chimica acta, 55 (1972), 317-328. An appreciative biography is C.H.Eugster, “Paul Karrer 1889-1971,” in Chemie in unserer Zeit,6 (1972), 146-153.
Henry M. Leicester