Why do organic chemists care about multistep synthesis
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A good illustration of the importance of organic synthesis comes with drug making. Throughout history, drugs have primarily been obtained from natural sources. The kings of Mesopotamia smoked poppies to get at the hallucinogenic properties of the opium alkaloids; Native Americans chewed aspirin-containing willow bark for pain relief; Fleming discovered Penicillin in a mould that grew on his staphylococcus bacteria plates. Still today, natural product chemists extract compounds from living things, characterize them, and test to see if those compounds have biological activity.

But extracting drugs from natural sources has its problems. Oftentimes, the source of a drug is an exotic plant or fungus that does not grow in large quantities. The extraction of these compounds can also be difficult, or the source may not produce it in large quantities. It is not uncommon to start with thousands of pounds of a source material and extract just a few paltry milligrams of the desired compound from it. Nature may be a far better synthetic organic chemist than humans can ever dream of becoming, but that does not mean that it produces the needed quantities of material on demand. Clearly, it would be impractical to take thousands of pounds of a species on the verge of extinction to make just a few small doses of a drug.

So what then is the answer to get the desired compounds? Multistep synthesis. Make the compounds from scratch. Take commercially available starting materials and build up the desired molecule using available reagents and techniques from the literature. A great many of the drugs that you can buy from pharmacies today were made by multistep syntheses, with enormous quantities of starting materials and reagents added with front-end loaders into gigantic reaction vessels. But all of that was first planned out on paper by chemists, plotting the shortest, cheapest, most elegant route available to the target compound (fortunately for those in a sophomore organic class, only the length of the synthesis is a factor).

Of course, that doesn't mean that the application of multistep synthesis is limited to drugs. It is not. It is used for many purposes, and one thing that is great about the ability to make compounds is that it gives the organic chemist free reign to pretty much do anything in chemistry (which is why biochemists and physical chemists are forced to collaborate with synthetic organic chemists if they want to get anything done). In some cases, multistep synthesis is even carried out for the act of synthesis itself, and there are those who synthesize molecules that have only "grant proposal activity" -- compounds that may show enough biological activity to fund a grant proposal, but not enough to make it to clinical trials -- and in these cases, multistep synthesis is used as a framework to develop new reactions, to test or to hone known reaction methods, and (let's face it) as a stomping grounds for chemists to flout their synthetic prowess.


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