Professor Nelson J. Leonard

Leading organic chemist who gave up a career as a concert baritone to devote his life to science

Nelson John Leonard, organic chemist and concert baritone: born Newark, New Jersey 1 September 1916; Assistant Professor of Chemistry, University of Illinois, Champaign-Urbana 1947-49, Associate Professor of Chemistry 1949-52, Professor of Organic Chemistry 1952-68, Professor of Chemistry 1968-81, Professor of Biochemistry 1973-86, Reynold C. Fuson Professor of Chemistry 1981-86 (Emeritus); Faculty Associate, California Institute of Technology 1992-2006; married 1947 Louise Vermey (died 1987; three sons, one daughter), 1992 Peggy Phelps; died Pasadena, California 9 October 2006.

A world leader in organic chemistry, Nelson J. Leonard was one of the first people to use chemistry to understand biology. He was also a musical artist of great distinction who had performed as a soloist with the Chicago, Cleveland and St Louis symphony orchestras.

At the time of Leonard's election (1955) as a member of the US National Academy of Science, it was open to him to continue his career as an academic or opt for one as a professional bass-baritone. He once confessed that, because of his election - the highest honour that American science can bestow - he had "better do something about it". That decision was influenced in part to having listened to a lecture by Alexander Todd (later Lord Todd, Nobel Laureate) of Cambridge University describing the importance and structures of the nucleic acids. "Todd's work was inspirational," he said.

For more than four decades Leonard was a professor at the University of Illinois at Champaign-Urbana, one of the hot-beds of organic chemistry in the United States. Here he pursued his research and teaching with flair and conspicuous success, directing over 120 PhD students and some 90 post-doctoral workers. He published over 400 papers and filed eight patents. The current head of the Urbana chemistry department, Steven C. Zimmerman, recalls that Nelson Leonard was "way ahead of his time . . . in the sense that he collaborated with biologists and biochemists long before interdisciplinary research was fashionable".

Starting in the 1960s, Leonard synthesised a variety of chemicals that were known to influence the growth and development of plants. For over 20 years he had a fruitful collaboration with the plant physiologist Folke Skoog, of the University of Wisconsin, where many of Leonard's new compounds were tested. Several of these compounds are now used in horticulture to stimulate the growth of intact plants, flowers and trees from tissue cultures.

Another important scientific contribution made by Leonard was to synthesise fluorescent variants of the nucleotide components of DNA and RNA as useful means to highlight their location within the living cell. Leonard's work has undoubtedly led to much of what is now known about the mode of action of cells. With the invention of the charge-coupled device and recent advances in cell microscopy, the fluorophore groups devised by Leonard have taken on a new significance, enabling molecular biologists to trace in vitro the "real-time" behaviour of single individual species such as enzymes.

In the course of the Second World War, he succeeded in synthesising a malaria drug known as chloroquine, which he produced just in time to be extensively used in the US Pacific campaign. After the war, he was recruited by the US Army to investigate the research publications of the giant German chemical company I.G. Farbenindustrie; and he and his colleagues found several processes that were later taken up by American companies, including a technique to improve the manufacture of synthetic rubber.

Nelson Leonard was born in Newark, New Jersey, in 1916 and grew up in Mount Vernon, New York, where, at high school, his interest in chemistry was kindled by a devoted schoolteacher, and by the fact that his father (a salesman) and mother (a housewife) had bought him a chemistry set. A glittering undergraduate career was pursued in Lehigh University, Bethlehem, Pennsylvania, where he sang frequently at the beautiful Packer Chapel, and from where he won a Rhodes Scholarship to Lincoln College, Oxford.

In an evocative and beautifully written autobiography entitled More than a Memoir (2006), Nelson Leonard describes how he became so charmingly anglophilic. On arrival in Plymouth, as he climbed up the Hoe he pondered the conquest of the Spanish Armada by Francis Drake. At Oxford he was mentored by N.V. Sidgwick and Leslie Sutton (later of Magdalen College); he sang in the college choir, frequently performed as a soloist in concerts, rowed in the college boat, became a lifelong friend of the college bursar, Keith Murray (later Lord Murray of Newhaven), and spent an occasional weekend in the home of the writer J.B. Priestley, whose daughter was his friend at Oxford.

The Second World War interrupted his career in 1939 when he returned to the US and enrolled for a PhD in Columbia University, New York. He graduated in 1942 and took up his first teaching post, at the University of Illinois at Champaign-Urbana.

At Urbana, he resumed his singing career. In his memoir, Leonard recalls the occasion (in 1952) when he sang the baritone part in Walton's Belshazzar's Feast with the Chicago Symphony Orchestra under the direction of the charismatic Czech conductor Rafael Kubelik. At the dress rehearsal, Nelson Leonard sang the famous aria:

Babylon was a great city. Her merchandise was of gold and silver, of precious stones, of pearls . . . wine and oil, fine flour, wheat and beasts, sheep, horses, chariots, slaves and the souls of men.

After he had finished this unaccompanied solo, Kubelik called a halt to the rehearsal and asked Leonard what he was thinking about when he sang the long list of wonders. Leonard replied that he started the list very slowly to indicate what was considered important to the Babylonians. Then he gradually accelerated and finished the phrasing so rapidly that "and the souls of men" became almost a throwaway line. Kubelik said,

Why not try it differently? Start with a faster listing of the merchandise and retard gradually, slower and slower until you end most slowly - and sarcastically - with "and the souls of men". Then the audience will appreciate the contrast.

At the actual performance, that is how Leonard did it. "I knew immediately that it had been much more effective. Kubelik winked at me."

After the death in 1987 of his first wife, Louise, and after retirement from Urbana, Leonard went as a Sherman Fairchild Distinguished Scholar to the California Institute of Technology in 1991. Later he accepted a faculty position at Caltech. His second wife, Peggy, shared with him numerous enthusiasms, especially for music and all the arts. They were both involved in the musical world in Pasadena, and he served on the board of the Pasadena Symphony.

Very few chemists that I have known could match Leonard's skill as a commentator and judge of scientific work, his own and that of others. I believe that all serious historians of science should read his perceptive article "The 'Chemistry' of Research Collaboration", published in Tetrahedron (1997) - a fascinating analysis that anatomises the process of research collaboration, its inception, expansion and completion. In it one sees how often the element of the unpredictable looms large in major scientific adventure.

John Meurig Thomas