Robert Burns Woodward (April 10, 1917–July
8, 1979) was an American organic chemist. He made many important contributions
to modern organic chemistry, especially in the synthesis and structure
determination of complex natural products, and worked closely with Roald
Hoffmann on theoretical studies of chemical reactions. Woodward won the Nobel
Prize in Chemistry in 1965.
Early life and education
Woodward was born in Boston, Massachusetts, the son of Arthur Woodward (an
immigrant from England) and Margaret Woodward, nee Burns (an immigrant from
Scotland, born in Glasgow).
From a very early age, Woodward was attracted to chemistry and engaged in
private study while he attended the public primary and secondary schools of
Quincy, Massachusetts. By the time he entered high school, he had already
managed to perform most of the experiments in Paul Gatterman's then widely used
textbook of experimental organic chemistry. In 1928, Woodward contacted the
Consul-General of the German consulate in Boston, and through him, managed to
obtain copies of a few original papers published in German journals. Later, in
his Cope lecture, he recalled how he had been fascinated when, among these
papers, he chanced upon Diels and Alder's original communication about the Diels-Alder
reaction. Throughout his career, Woodward was to repeatedly and powerfully use
and investigate this reaction, both in theoretical and experimental ways. In
1933, he entered the Massachusetts Institute of Technology (MIT), but neglected
his formal studies badly enough to be expelled the next year. MIT readmitted him
in 1935, and by 1936 he had received the Bachelor of Science degree. Only one
year later, MIT awarded him the doctorate, when his classmates were still
graduating with their bachelor's degrees. Woodward's doctoral work involved
investigations related to the synthesis of the female sex hormone estrone. After
a short postdoctoral stint at the University of Illinois, he took a Junior
Fellowship at Harvard University from 1937 to 1938, and remained at Harvard in
various capacities for the rest of his life. In the 1960s, Woodward was named
Donner Professor of Science, a title that freed him from teaching formal courses
so that he could devote his entire time to research.
Early work
The first major contribution of Woodward's career in the early 1940s was a
series of papers describing the application of ultraviolet spectroscopy in the
elucidation of the structure of natural products. Woodward collected together a
large amount of empirical data, and then devised a series of rules later called
the Woodward rules, which could be applied to finding out the structures of new
natural substances, as well as non-natural synthesized molecules. The expedient
use of newly developed instrumental techniques was a characteristic Woodward
exemplified throughout his career, and it marked a radical change from the
extremely tedious and long chemical methods of structural elucidation that had
been used until then.
In 1944, with his post doctoral researcher, William von Doering, Woodward
completed the synthesis of the alkaloid quinine, used to treat malaria. Although
the synthesis was publicized as a breakthrough in procuring the hard to get
medicinal compound from Japanese occupied southeast Asia, in reality it was too
long and tedious to adopt on a practical scale. Nevertheless it was a landmark
for chemical synthesis. Woodward's particular insight in this synthesis was to
realise that the German chemist Paul Rabe had converted a precursor of quinine
called quinotoxine to quinine in 1905. Hence, a synthesis of quinotoxine (which
Woodward actually synthesized)) would be tantamount to synthesizing quinine.
When Woodward accomplished this feat, organic synthesis was still largely a
matter of trial and error, and nobody thought that such complex structures could
actually be constructed. Woodward showed that organic synthesis could be made
into a rational science, and that synthesis could be aided by well-established
principles of reactivity and structure. This synthesis was the first one in a
series of exceedingly complicated and elegant syntheses that he would undertake.
Later work and its impact
Culminating in the 1930s, the British chemists Christopher Ingold and Robert
Robinson among others had investigated the mechanisms of organic reactions, and
had come up with empirical rules which could predict reactivity of organic
molecules. Woodward was perhaps the first synthetic organic chemist who used
these ideas as a predictive framework in synthesis. Woodward's style was the
inspiration for the work of hundreds of successive synthetic chemists who
synthesized medicinally important and structurally complex natural products.
Organic syntheses and Nobel Prize
During the late 1940s, Woodward synthesized many complex natural products
including quinine, cholesterol, cortisone, strychnine, lysergic acid, reserpine,
chlorophyll, cephalosporin, and colchicine. With these, Woodward opened up a new
era of synthesis, sometimes called the 'Woodwardian era' in which he showed that
natural products could be synthesized by careful applications of the principles
of physical organic chemistry, and by meticulous planning.
Many of Woodward's syntheses were described as spectacular by his colleagues and
before he did them, it was thought by some that it would be impossible to create
these substances in the lab. Woodward's syntheses were also described as having
an element of art in them, and since then, synthetic chemists have always looked
for elegance as well as utility in synthesis. His work also involved the
exhaustive use of the then newly developed techniques of infrared spectroscopy
and later, nuclear magnetic resonance spectroscopy. Another important feature of
Woodward's syntheses was their attention to stereochemistry or the particular
configuration of molecules in three dimensional space. Most natural products of
medicinal importance are effective, for example as drugs, only when they possess
a specific stereochemistry. This creates the demand for 'stereospecific
synthesis', producing a compound with a defined stereochemistry. While today a
typical synthetic route routinely involves such a procedure, Woodward was a
pioneer in showing how, with exhaustive and rational planning, one could conduct
reactions that were stereospecific. Many of his syntheses involved forcing a
molecule into a certain configuration by installing rigid structural elements in
it, another tactic that has become standard today. In this regard, especially
his syntheses of reserpine and strychnine were landmarks.
Woodward also applied the technique of infrared spectroscopy and chemical
degradation to determine the structures of complicated molecules. Notable among
these structure determinations were santonic acid, strychnine, magnamycin and
terramycin. During the war years, Woodward also proposed the correct structure
of penicillin as a beta-lactam, as opposed to the thiazolidine-oxazolone
structure proposed by Robert Robinson, the then leading organic chemist of his
generation. About terramycin, Woodward's colleague and Nobel Laureate Derek
Barton said:
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 much 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.
In each one of these cases, Woodward again showed how rational facts and
chemical principles, combined with chemical intuition, could be used to achieve
the task.
In the early 1950s, Woodward, along with the British chemist Geoffrey Wilkinson,
then at Harvard, postulated a novel structure for ferrocene, a compound
consisting of a combination of an organic molecule with iron. This marked the
beginning of the field of organometallic chemistry which grew into an
industrially very significant field. Wilkinson won the Nobel Prize for this work
in 1973, along with Ernst Otto Fischer. Some historians think that Woodward
should have shared this prize along with Wilkinson. Remarkably, Woodward himself
thought so, and voiced his thoughts in a letter sent to the Nobel Committee.
Woodward won the Nobel Prize in 1965 for his synthesis of complex organic
molecules. In his Nobel lecture, he described the total synthesis of the
antibiotic cephalosporin, and claimed that he had pushed the synthesis schedule
so that it would be completed around the time of the Nobel ceremony.
B12 synthesis and Woodward-Hoffmann rules
In the early 1960s, Woodward began work on what was the most complex natural
product synthesized to date- Vitamin B12. In a remarkable collaboration with his
colleague Albert Eschenmoser in Zurich, a team of almost one hundred students
and postdoctoral workers worked for many years on the synthesis of this molecule.
The work was finally published in 1973, and it marked a landmark in the history
of organic chemistry. The synthesis included almost a hundred steps, and
involved the characteristic rigorous planning and analyses that had always
characterised Woodward's work. This work, more than any other, convinced organic
chemists that the synthesis of any complex substance was possible, given enough
time and planning. However, as of 2005, no other total synthesis of Vitamin B12
has been published.
That same year, based on observations that Woodward had made during the B12
synthesis, he and Roald Hoffmann devised rules (now called the Woodward-Hoffmann
rules) for elucidating the stereochemistry of the products of organic reactions.
Woodward formulated his ideas (which were based on the symmetry properties of
molecular orbitals) based on his experiences as a synthetic organic chemist; he
asked Hoffman to perform theoretical calculations to verify these ideas, which
were done using Hoffmann's Extended Hückel method. The predictions of these
rules, called the "Woodward-Hoffmann rules" were verified by many experiments.
Hoffmann shared the 1981 Nobel Prize for this work along with Kenichi Fukui, a
Japanese chemist who had done similar work using a different approach; Woodward
undoubtedly would have received a second Nobel Prize as well had he lived.
Woodward Institute and later life
While still remaining at Harvard, Woodward took on the directorship of the
Woodward Research Institute, based at Basel, Switzerland in 1963. He also became
a trustee of his alma mater, MIT, from 1966 to 1971 and of the Weizmann
Institute of Science in Israel.
Woodward died in Cambridge, Massachusetts from a heart attack in his sleep. At
the time, he was working on the synthesis of an antibiotic, erythromycin. A
student of his said about him:
I owe a lot to R. B. Woodward. He showed me that one could attack difficult
problems without a clear idea of their outcome, but with confidence that
intelligence and effort would solve them. He showed me the beauty of modern
organic chemistry, and the relevance to the field of detailed careful reasoning.
He showed me that one does not need to specialize. Woodward made great
contributions to the strategy of synthesis, to the deduction of difficult
structures, to the invention of new chemistry, and to theoretical aspects as
well. He taught his students by example the satisfaction that comes from total
immersion in our science. I treasure the memory of my association with this
remarkable chemist.
Many regard Woodward to be the pre-eminent organic chemist of the latter half of
the twentieth century.
Other notes
In 1938 he married Irja Pullman, and in 1946 he married Eudoxia Muller. From the
first marriage he had two daughters, and from the second one daughter and one
son.
During his lifetime Woodward 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 was published even till a few years after his death.
Woodward trained more than two hundred talented PhD. students and postdoctoral
workers, many of who later went on to distinguished careers. Some of his best-known
students include Yoshito Kishi (Harvard), Stuart Schreiber (Harvard), Steven A.
Benner (UF), Christopher S. Foote (UCLA), Kendall Houk (UCLA), and world-renowned
porphyrin chemist and former Vice Chancellor of the University of California-Davis,
Prof. Kevin M. Smith. Smith was recently awarded the Robert Burns Woodward Award
for Lifetime Achievement at the International Conference on Porphyrins and
Pthalocyanines (ICPP- 4) held at Rome.
Woodward was known to be a workaholic and devoted almost all his time to
chemistry. He had an encyclopaedic knowledge of chemistry, and an extraordinary
memory for detail. Probably the quality that most set him apart from his peers
was his remarkable ability to tie together disparate threads of knowledge from
the chemical literature and bring them to bear on a chemical problem. His
lectures were legendary and frequently used to last for three or four hours. In
many of these, he eschewed the use of slides and used to draw beautiful
structures by using coloured chalk. His famous Thursday seminars at Harvard also
used to frequently last well into the night. He had a fixation with blue, and
all his suits, his car, and even his parking space were coloured in blue. He
detested exercise, could get along with only a few hours of sleep every night,
was a heavy smoker, and enjoyed Scotch whisky and a martini or two.
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