Pure chemists around the world last week celebrated reclaiming 鈥榯heir鈥�
Nobel prize from the biologists and physicists who had seized the crown
in recent years. This year鈥檚 prizewinner is Elias J Corey, an organic chemist
at Harvard University, who revolutionised the thinking behind the synthesis
of organic molecules. 鈥業t鈥檚 a long-overdue recognition of the work he鈥檚
done. Chemistry has had less than its fair share of the prizes recently,鈥�
said Peter Johnson, of the University of Leeds.
Corey鈥檚 greatest achievement was to develop a new framework for devising
synthetic pathways 鈥� the sequences of reactions that lead to a target product.
In what he termed 鈥榬etrosynthetic analysis鈥�, Corey worked backwards from
the target compound to the point where he could retrace the steps to rebuild
the product 鈥� from simple, cheap starting materials.
鈥楾he best chemists had always done this sort of thing intuitively but
without formalising the logic behind their strategies,鈥� said Johnson. 鈥楬e
introduced the language of doing it. It鈥檚 still an art today, but it was
more of a black art before Corey came along and systematised it.鈥�
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Organic synthesis is notoriously difficult, even for experienced chemists,
because there are so many possible routes to each compound. Corey鈥檚 theories
and methods made possible the synthesis of very complex organic compounds,
many of which are important in medicine but could previously be obtained
from natural sources only in tiny quantities.
Corey made his first attempts at retrosynthetic analysis in the 1960s.
Starting with the target molecule, he broke it down into smaller and smaller
parts, working out which bonds needed breaking as he went along. From these
simpler fragments, he was able to rebuild the molecule using the simplest
possible reactions at each step and making the whole process more efficient.
Organic chemists have applied Corey鈥檚 theory to the synthesis of biologically
active natural compounds that were impossible to make commercially before.
鈥楾here is not a pharmaceuticals company in the world that has not used the
discoveries from our lab,鈥� said Corey last week. 鈥楽ynthesis is one of the
major forces behind progress in the world. It is going to be crucial to
the maintenance of our standard of living and to the solution of world problems
(such as) health and population.鈥�
Corey has synthesised around 100 such compounds himself. These include
porstaglandins, hormone-like substances that regulate a range of biological
functions, including contractions during childbirth. Only last year Corey
synthesised (+)-ginkgolid, the active substance from the ginkgo tree. The
worldwide sales of this natural product 鈥� used to treat asthma and circulatory
disorders 鈥� could reach $500 million (about 256 million Pounds a year.
鈥楬e鈥檚 made an outstanding contribution to synthesis. He produced 50
and 100 new chemical reagents and reactions. Most chemists would be happy
if they鈥檇 developed just one or two,鈥� said Johnson.
Dudley Herschbach, another chemist from Harvard, who won a Nobel prize
in 1986, says that chemical synthesis 鈥榮hould be thought of as a great modern
art form. The architecture of creating these molecules is really akin to
what we admire in Beethoven or Mahler,鈥� he said.
