Like for instance, tamoxifen…what would a chemist use as the raw material? Or for any other drug. If a chemist decides he wants to make something from scratch, what does he use for the scratch?
(IANAChemist, but I have been working in the pharma industry for many years)
There are hundreds of thousands of readily available chemical reagents out there. It is quite common for chemists to have an idea for a small molecule that they would like to produce and then do umpteen different kinds of chemical structure searches in a chemistry database.
MDL offers a well-known catalog called Available Chemical Directory (ACD) that many use to find vendors who sell useful starting components. This directory has hundreds of thousands of chemical structures and millions of catalog line items from many thousands of vendors.
Here’s how it might work: you might want to make something that looks like a benzene ring with a few widgets hanging off it and a dongle on the side. You simply use a tool like ChemDraw to sketch out the critical bits of the structure, paste it into your database query tool, and then perform a sub-structure search across your entire library of compounds: both proprietary compounds made in house as well as catalogs such as ACD. You will hopefully find some stuff that is pretty close to what you want.
If you have it in-house, you can order it from your compound room (and we’re talking about a few milligrams, most likely), or else you go to an external supplier such as Sigma Aldrich and order a bottle.
From that point, you use standard chemistry techniques to chop bits up and combine other bits.
There are all kinds of other interesting stuff folks do such as combinatorial chemistry, where they start with a given chemical structure and bolt various things onto it, producing many other compounds. You can even buy libraries of compounds that have secret identities: when you find one that responds nicely to your screening tests, pay the vendor to get the details of the compound.
Besides the relatively small bits of “fancy” specialty chemicals, chemists also consume larger amounts of standard reagents. A typical pharmaceutical company will have a well-stocked chemical stockroom with solvents, acids, distilled water, and other useful things.
Tamoxifen synthesis begins with a simple friedel-craft acylation between Anisole and Phenylacetic acid.. Or you can start by carbometallating phenyltrimethyl silyl acetylene with diethylaluminium chloride.
Tamoxifen synthesis is a straight out, hard core exercise in organic chemistry. They don’t even use a fungal enzyme to tack a hydroxyl group onto the final organic product.