Page 63 - Visions of the Future Chemistry and Life Science

52 J. M. GOODMAN

more powerful very rapidly, but will they become more powerful by a suf-
ficient amount for this problem?
We can obtain a crude estimate the time required for a precise
quantum mechanical calculation to analyse possible syntheses of bryosta-
tin. First, the calculation of the energy of a molecule of this size will take
hours. Many such calculations will be required to minimise the energy of
a structure. A reasonable estimate may be that a thousand energy calcula-
tions would be required. Conformation searching will require many such
minimisations, perhaps ten thousand. The reactivity of each intermediate
will require a harder calculation, perhaps a hundred times harder. Each step
will have many possible combinations of reagents, temperatures, times,
and so on. This may introduce another factor of a thousand. The number
of possible strategies was estimated before as about a million, million,
million. In order to reduce the analysis of the synthesis to something
which could be done in a coffee break then computers would be required
30
which are 10 times as powerful as those available now. This is before the
effects of solvents are introduced into the calculation.
Dr Gordon E. Moore, the co-founder of Intel, the computer chip
company, predicted that computers would double in power about every
two years, without increasing in price. ‘Moore’s Law’ has held good for
almost 30 years. If Moore’s law continues to hold true, it will be 200 years
before it is possible to analyse a synthesis in a coffee break, and then begin
to think about solvents. Moore’s law is based on the idea that it will be pos-
sible to double the density of components on computer chips every two
years. If this is to continue for the next two centuries, it will be necessary
to have circuits very much smaller than atoms! It is unlikely that Moore’s
law will continue to hold for so long. The estimate of the time required is
a crude one, and algorithmic advances will undoubtedly play a part in
making the problem easier, but it will certainly be a long time before com-
puters can conquer synthesis by brute force.
Can computers, therefore, have any hope of being competing with
humans at synthesis, or will people maintain supremacy over machines for
the foreseeable future? Fortunately for computers, there is another
approach to solving the problem of chemistry. In the introduction to his
book, The Nature of the Chemical Bond (Pauling 1945), Pauling gives his
opinion that it should be possible to describe structural chemistry in a
satisfactory manner without the use of advanced mathematics. Books such
as this have probably been more influential in the development of modern