One of the greatest challenges in organic chemistry is mimicking the incredibly complex mechanisms Nature uses to synthesize molecules. Chemists have wondrous technologies and intricate techniques at their disposal, but these pale in comparison to the power of living systems (with their many enzymes, which act as catalyst) to produce complicated molecular structures.
One entire branch of organic chemistry is known as “total synthesis”. Put simply, it involves choosing a promising candidate molecule – maybe something that has shown anti-cancer properties, or other interesting behavior – and then developing a plan to synthesize that molecule, from “scratch”, in the laboratory. Using nothing more than common starting materials available from any chemical supply company, the chemists painstakingly go through dozens, sometimes many dozens, of separate intricate synthetic steps to end up with the final, desired molecule.
Given that these molecules are found in nature (sometimes abundantly), some may question the need for such elaborate “total synthesis”. To give an analogy, trees are everywhere; why would we want to create a tree from water / coal / trace nutrients? However, it is these epic marathon efforts to produce a complicated molecule from total synthesis that often give chemists new reactions and new understanding of chemical behavior. Nobel prizes have been awarded for such work, and the field of organic chemistry is richer for the efforts of those brave souls who piece together such amazingly complicated molecules from simple building blocks.
One recently published successful total synthesis (appearing in Angewandte Chemie, one of Germanys top science journals) is the culmination of over twenty years of work. The molecule in question is called azadirachtin, and it’s an insecticide that is biodegradable, non toxic towards humans, and very harmful to the insect pests who feed on plant crops. It is found naturally in certain trees on the subcontinent but not in sufficient quantities for the trees to be an economically viable source. Dozens of organic chemists worked on this synthesis. The accomplishment is even more notable given that the finished product is unstable in the presence of light as well as towards pH changes. This makes it an incredibly tricky material to synthesize, and just imagine the frustration if you are months into the project and the batch you’ve prepared gets exposed to light for a brief moment! Everything is ruined, and you have to start right back in the beginning. It’s maddening.
The techniques and new synthetic methods developed throughout this twenty year voyage of discovery will no doubt lead new generations of organic chemists to exciting discoveries. Not only is this accomplishment a triumph in its own right, but it is a stunning example of the ingenuity of organic chemists.
Source for this article:
“Synthesis of Azadirachtin: A Long but Successful Journey”
Veitch, G. E.; Beckmann, E.; Burke, B. J.; Boyer, A.; Maslen, S. L.; Ley, S. V. Angewandte Chemie2007, 46, 7629-7632.
Angewandte Chemie , a publication of the Gesellschaft Deutscher Chemiker.