«NATIONAL ACADEMY OF SCIENCES ROBERT BURNS WOODWARD 1917–1979 A Biographical Memoir by ELKAN BLOUT Any opinions expressed in this memoir are those ...»
NATIONAL ACADEMY OF SCIENCES
ROBERT BURNS WOODWARD
A Biographical Memoir by
Any opinions expressed in this memoir are those of the author
and do not necessarily reflect the views of the
National Academy of Sciences.
Biographical Memoirs, VOLUME 80
P U B L I S H ED BY
THE NATIONAL ACADEMY PRESSW A S H I N G T O N, D.C.
R O B E R T B U R N S W O O D WA R DApril 10, 1917–July 8, 1979
BY ELKAN BLOUTR was the preeminent organic chemist
OBERT BURNS WOODWARDof the twentieth century. This opinion is shared by his colleagues, students, and by other distinguished chemists.
Bob Woodward was born in Boston, Massachusetts, and was an only child. His father died when Bob was less than two years old, and his mother had to work hard to support her son. His early education was in the Quincy, Massachusetts, public schools. During this period he was allowed to skip three years, thus enabling him to finish grammar and high schools in nine years. In 1933 at the age of 16, Bob Woodward enrolled in the Massachusetts Institute of Technology to study chemistry, although he also had interests at that time in mathematics, literature, and architecture. His unusual talents were soon apparent to the MIT faculty, and his needs for individual study and intensive effort were met and encouraged.
Bob did not disappoint his MIT teachers. He received his B.S. degree in 1936 and completed his doctorate in the spring of 1937, at which time he was only 20 years of age.
Immediately following his graduation Bob taught summer school at the University of Illinois, but then returned to Harvard’s Department of Chemistry to start a productive period with an assistantship under Professor E. P. Kohler.
4 BIOGRAPHICAL MEMOIRSHe remained at Harvard until his death in 1979. Although Bob remained formally at Harvard for his entire professional life, he traveled extensively in order to lecture, receive awards, and sometimes to relax for a day or two with friends.
During the period 1945 through 1978 he received 24 honorary degrees. He was also the recipient of 26 medals and awards, which included the most prestigious in the world of chemistry. He was elected to the National Academy of Sciences in 1953 at the notably young age of 36. In addition, Bob was elected to membership in numerous academies and learned societies. A more complete and personal biographical summary, including a listing of his honors and awards, can be found in the Royal Society memoir by Lord Todd and Sir John Cornforth.1 What kind of a person was Bob, and how do we remember him? He was a genius and a very sensitive individual with a prodigious memory. He also had a drive to solve difficult problems and liked teaching in the broadest sense of the word. His lectures were models of clarity, originality, and insight. He enjoyed starting at the upper left-hand corner of a very large blackboard and finishing at the lower righthand corner with precise formulation of his ideas and thoughts and a total package that was characteristically Woodwardian. He really relished lecturing to students and to colleagues, but he did not enjoy formal courses. Fortunately, in the middle of his Harvard career, Bob was given an endowed professorship in 1962 that eliminated the need for him to teach regular courses. However, he maintained, “I teach all the time so that I don’t have to teach formal courses.” He taught in the laboratory, in seminars, and via lectures, so here was no question that he was an expert in this kind of teaching.
He accomplished much in several diverse areas (e.g., the correlation of various physical methods with organic
ROBERT BURNS WOODWARDstructures, determination of the structures of complex compounds, the syntheses of many naturally occurring biological compounds, and devising beautiful and concise synthetic pathways for complicated molecules). Last but not least, he had a deep appreciation of the wonders of nature and often attempted to understand many of the relations between the biological world, the chemical world, and the synthetic chemistry world in which he practiced so adroitly. Among the achievements of Woodward in the field of organic synthesis are the total syntheses of quinine, steroids, strychnine, reserpine, chlorophyll, and, finally, one of the most important and complicated naturally occurring molecules, vitamin B12.
During his lifetime he authored or coauthored 196 publications, of which 85 are full papers, the remainder comprising preliminary communications, the text of lectures, and reviews. The pace of his scientific activity soon outstripped his capacity to publish all experimental details, and much of the work he participated in is even now being published by his colleagues and coworkers.
In preparing this review I was assisted by written communications relating to Bob’s work by Derek Barton, Albert Eschenmoser, and Roald Hoffmann. Many of his students and postdoctoral fellows wrote to describe their feelings, attitudes, and assessments of Bob Woodward as a mentor, as a teacher, and as a friend. We regret that space does not allow us to include many of these statements, but we will do our best to present the feelings of some of them in the next sections.
(WITH INPUT FROM DEREK BARTON)In 1948, when he was 31, Woodward gave a brilliant lecture at Imperial College, London, on the structure of santonic acid. He spoke without notes or slides and covered
6 BIOGRAPHICAL MEMOIRSthe blackboard with beautifully drawn formulae. He argued that santonic acid, a compound obtained from santonin and hitherto without a structure, was formed by the basecatalyzed opening of the lactone ring with alpha-beta double bond shift to give a keto-acid, the anion of which cyclized to give santonic acid. He showed that the latter must be a derivative of cis-decalin.
Every scientist must be judged by the standards of his time. In 1948 we had never heard anyone pose, and then resolve, a problem in such a clear and logical manner. Woodward was the first to show that problems in chemistry could be solved by thinking about them. The scientific world first heard of Woodward between 1940 and 1942 because of his publications on the correlation of ultraviolet spectra with structure (1941,1942). He next became famous for the formal synthesis of quinine (1944), in association with W. von E. Doering.2 This was Woodward’s first multistep synthesis.
For this synthesis he immediately gained the respect of the older generations of organic chemists.
Woodward was exceptionally gifted in deducing structures. At a time when physical methods were not yet perfected he could integrate an enormous number of facts, both clear and misleading, into a coherent whole better than any chemist who had ever lived. During World War II he started with a reasoned argument (1944) for the betalactam formula for penicillin, in contrast to the incorrect oxazoline formula advocated by Sir Robert Robinson and others.
The problem of the structure of strychnine had been a challenge to organic chemists for more than a century.
Robinson had worked hard and well on this subject for many years, and immediately after the war he made it his major project. It was a perfect challenge for Woodward.
There was an enormous body of fact that, with the aid of a
ROBERT BURNS WOODWARDminimum of concise experimentation, led him to deduce the correct formula (1954).
In 1949 Barton was invited to spend a year at Harvard to replace Woodward, who was on sabbatical leave. It was no surprise to anyone also that Woodward stayed exactly where he was. At that time his evening seminars were marvelous, with Gilbert Stork also participating in a stimulating way. In theory a speaker would be recruited to talk about his work starting at 8:00 p.m., but in fact at approximately 8:30 p.m. The speaker would be closely questioned by all.
At about 10:00 p.m. Woodward would pose a problem from the literature. Guests and students would then spend up to an hour trying to solve this problem. When they had all failed Woodward would give his solution, which was always correct. He would then call for anyone else to pose a problem.
This being done, it was usually Woodward who proposed the correct answer first. However, this was somewhat unfair, because as midnight approached Woodward got better and better; at least it seemed like that, while others tired.
The most brilliant analysis ever done on a structural puzzle was surely the solution (1953) of the terramycin problem. It was a problem of great industrial importance, and hence many able chemists had performed an enormous amount of work trying to determine the structure.
There seemed to be too many data to resolve the problem, because a significant number of observations, although experimentally correct, were very misleading. Woodward took a large piece of cardboard, wrote on it all the facts and, by thought alone, deduced the correct structure for terramycin.
Nobody else could have done that at the time.
The first major synthesis by Woodward after quinine was that of the steroid nucleus, including cholesterol (1951) and cortisone (1951). Woodward went to the United Kingdom in 1951 to deliver a Centenary Lecture. He spoke about
8 BIOGRAPHICAL MEMOIRShis total synthesis of steroids, which was brilliant, and all in the audience were impressed when he showed the formula and said that this was known as chrismasterol because it was first synthesized on Christmas day in 1950.
The next important target chosen was strychnine (1954).
Strychnine had five asymmetric centers, and therefore would seem to be a difficult objective. However, Woodward realized that the constitution of the molecule was such that it defined its own configurations and that a total synthesis should be relatively easy. An elegant synthesis was planned and executed with highly talented collaborators, again in a short time.
During the same époque Woodward and Barton collaborated on another total synthesis (by relay). The determination of the structure (1954) of lanosterol suggested to Woodward that this biosynthetically important compound should be synthesizable by the addition of three methyl groups to cholesterol, whose total synthesis he had just accomplished more easily than expected.
Woodward now began what may be the most beautiful synthesis of his life, the synthesis (1956) of the medicinally important alkaloid reserpine. This synthesis was meticulously planned and executed in less than two years by a highly gifted group of coworkers. It was a challenging stereochemical problem, and it was a pleasure to see how skillfully he used the now mature theory of conformational analysis.
Now we come to the funding of the Woodward Institute in Basel by the Ciba Company. Ciba research was reorganized with Dr. Heusler, who had participated in the Woodward steroid synthesis, joining the new Woodward Institute, directed by Woodward. Their first project was the synthesis of cephalosporin C starting with L-cysteine, and he produced an elegant and sophisticated synthesis that was completed just in time (1966) for the Nobel Prize ceremony in
ROBERT BURNS WOODWARD
1965. The Woodward Institute continued to do good work until his death.
This account of Woodward’s earlier scientific life reflects his unique intellectual superiority in his own generation. In the 1940s he was already a mature and apparently self-assured young man who knew more organic chemistry than anyone else did, and who could instantly integrate the remembered facts to face a new challenge. He pretended to be lazy and to be without ambition; he was just the opposite. In the 1950s his work in several areas reached a level of brilliance that may never be equaled.
(WITH INPUT FROM ROALD HOFFMANN)In 1983 Woodward gave a lecture at an American Chemical Society meeting in which he described his pleasure at seeing the original publication by Diels and Alder describing the discovery of the reaction that bears their name and his lifetime preoccupation with that reaction. He made use of the Diels-Alder reaction in a marginally commendable (in his own words) approach to the synthesis of oestrone during the middle 1930s in the course of his work for his Ph.D.
degree. Much later he used the Diels-Alder reaction with greater effect in the syntheses of cholesterol, cortisone, and reserpine. And beginning in 1939 he remembered that he pursued a number of investigations explicitly concerned with the detailed course and mechanism of Diels-Alder reactions.
Theoretically, interesting molecules always intrigued Woodward. The paper that marks the beginning of modern organometallic chemistry, the assignment of the correct sandwich structure of ferrocene, bears not only the name of one of the future leaders of the field, Geoffrey Wilkinson, but also of Woodward and two of his coworkers, M. Rosenblum and M. C. Whiting.
10 BIOGRAPHICAL MEMOIRS It is likely that it was his colleague William Moffitt who sharpened Woodward’s perception of modern theoretical chemistry and introduced him to molecular orbital theory.
Though the remarkable generalization that is the octant rule was initially empirically formulated by Woodward, Klyne, and Djerassi, the theoretical support it received from Moffitt and Moscowitz was essential (1961).