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The Nobel Prize in Chemistry 1987
Donald J. Cram, Jean-Marie Lehn, Charles J. Pedersen

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Award Ceremony Speech

Presentation Speech by Professor Salo Gronowitz of the Royal Academy of Sciences

Translation form the Swedish text

Your Majesties, your Royal Highnesses, Ladies and Gentlemen,

A prerequisite for all life processes is that molecules recognize each other and bind to each other in order to be able to react. The molecules are said to form complexes. The proteins in our food bind to other proteins, called enzymes, which catalyze – – – that is accelerate – – – their breakdown. Other compounds recognize ions, such as sodium and potassium, and transport them in and out of the living cell. Our biological defence against intruders is based on the formation of antibodies, which recognize the enemy, the antigen, and disarm him by forming harmless complexes. Our whole life, our consciousness, our instincts are governed by signal substances that are recognized by various receptors.

This biological recognition is very specific and selective. As the great chemist Emil Fischer, who received the Nobel Prize in chemistry in 1902, formulated it: The two molecules have to fit like a key in a lock. However, the lock is always a very complicated molecule of high molecular weight, a protein or a nucleic acid.

Organic chemists have been wondering for a long time, how much of the very large biomolecule is really necessary for achieving the desired result. How much of the molecule is really needed to form the hole or cleft in which the key has to fit for the reaction to take place. Organic chemists have dreamt about preparing molecules that mimic biomolecules in the laboratory, molecules that for instance have the same catalytic effects as enzymes, which chemical evolution has taken millions of years to develop.

A breakthrough towards this goal occurred when Charles Pedersen in the 1960's prepared cyclic compounds that contained carbon and oxygen atoms in rings of 18 up to 40 atoms. As their form was similar to a royal crown, he called these new compounds crown ethers. He showed that these compounds had many peculiar and unexpected properties. For example, they formed strong complexes with the alkali metal ions, lithium, sodium, potassium, rubidium and cesium, which previously had been difficult to bind. Of these spherical ions, lithium is the smallest and cesium the largest. Depending upon the size of the synthesized crown, potassium, for example, could tit inside, while the cesium ion was too large to be trapped.

The explosive development of the art of organic synthesis during the last decades, which is reflected in the Nobel Prizes in Chemistry to Robert Woodward in 1965, to Herbert Brown and Georg Wittig in 1979 and to Bruce Merrifield in 1984, has made it possible for Donald Cram and Jean-Marie Lehn to very skilfully design more complex molecules containing holes and clefts which bind inorganic as well as organic positive ions even more selectively. Other synthetic molecules can bind various negative ions as well as neutral molecules. Even molecules which can differentiate between mirror image forms of a molecule have been prepared. It has also been possible to synthesize molecules which enzymes in their mode of action and strongly accelerate various types of chemical reactions. Other organic compounds have been prepared which transport ions through biological membranes. By means of their penetrating investigations the laureates have also elucidated the factors that govern complex formation, and the changes that occur in both partners' chemical and physical properties, and how this can be used in practice for different purposes.

Through their work the laureates laid the foundation to what today is one of the most expansive chemical research areas, for which Cram has coined the term host-guest chemistry, while Lehn calls it supramolecular chemistry. Their research has been of enormous importance for the development of coordination chemistry, organic synthesis, analytical chemistry, bioinorganic and bioorganic chemistry, it is no longer science fiction to prepare supermolecules which are better and more versatile catalysts than the highly specialized enzymes. The dream may soon become reality. Through their work Cram, Lehn and Pedersen have shown the way.

Professor Cram, Professor Lehn, Mister Pedersen, in these few minutes I have tried to explain your fundamental work in the field of molecular recognition and the great importance and consequences your results have in many branches of chemistry, such as analytical chemistry, organic synthesis, coordination chemistry and bioinorganic and bioorganic chemistry. You have indeed shown, as the father of organic synthesis, Marcelin Berthelot, Professor at College de France, formulated it more than a century ago "La Chimie crée ses objets".

In recognition of your important contributions to chemistry the Royal Academy of Sciences has decided to confer upon you this year's Nobel Prize for Chemistry.

It is an honour and a pleasure for me to extend to you the congratulations of the Royal Academy of Sciences, and to ask you to receive your prizes from the hands of his Majesty the King.

From Nobel Lectures, Chemistry 1981-1990, Editor-in-Charge Tore Frängsmyr, Editor Bo G. Malmström, World Scientific Publishing Co., Singapore, 1992

 

Copyright © The Nobel Foundation 1987
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