Grand Designs: Synthesis

In this final reaction I am going to show you in the broadest of outlines how chemists build the equivalent of a cathedral. That is, how they synthesize a complicated molecule from scratch. The aim of a synthesis is to take a reasonably readily available laboratory chemical and process it—add bits on, take things off, close rings of atoms, open rings, build flying buttresses, and so on—until the target compound has been made. You could take the view that you should really start from absolute scratch, from the elements themselves, typically hydrogen, carbon, nitrogen, and oxygen, and build the molecule from those. However, that would be a waste of time and not crucial to the demonstration of the synthetic route because it is possible to argue that there are already plenty of methods for synthesizing the simple starting materials from scratch, and the real challenge is to build the intricate molecule. That is rather like accepting that a contractor can supply windows, bricks, and beams when constructing a real house and that it isn’t necessary to go all the way back to the sand, clay, and iron ore from which they are made to demonstrate that the house can be built literally from the ground up. Of course, the starting materials in a modern chemical synthesis might seem a bit recondite, but be assured that they are reasonably acceptable and purchasable from suppliers of laboratory reagents or easily made from what they do supply. Now for the particular cathedral on which I intend to focus. That scourge of humanity, malaria (‘bad air’), was introduced into the New World in the fifteenth century and soon wrought the havoc that had for long, and still, afflicts millions. The natives there found that an extract of the bark of the quina-quina tree, in due course to be classified as Cinchona Officinalis, was an effective cure, in particular having saved the life of the Countess of Cinchona. In due course the active component, quinine, was identified and extracted.