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The most important contribution that I made in science


Working on natural products chemistry
Carl Djerassi Scientist
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In Mexico I was entirely a synthetic chemist... Making things with an object to make them, so that they can be used for medicinal purposes, mostly by synthetic chemists, but the cacti... and it really started with that. Interest aroused my curiosity what’s in them, and that led me to start working on cactus chemistry. Now there were very few people worked on cactus chemistry, there was really only one natural product that was famous, if not notorious, and that was mescaline from peyote buttons, but these were small cacti. They were from Mexico, but they were small, and not the really giant treelike ones here, and so I focused on that and we did... I probably did maybe a dozen PhD thesis’, and many post docs who worked on the constituents of giant cacti, and we did some very important work. And it had no... there were no practical consequences of this, and I didn’t even mean there to be, but chemically they were extremely interesting, and that led me also to alkaloid work, and to... what I really found were interesting, triterpines, and triterpines are compounds that look like... like steroids, but are even more complex. I don’t know whether I have some... I may have some structures in here? No, probably not. Chemical structures, but I worked on these, and that led me to alkaloid chemistry, and that led me to antibiotic chemistry, but it led me to the structure elucidation of compounds, rather than to the synthesis of it. And structurally I’ll use, not quite an architectural metaphor, which you try to use for synthesis, to try and draw the difference between total synthesis and partial synthesis, but a different one, and at that time it was, I think for me, intellectually an even more challenging one, and it was something which was primarily practised in Europe, and later also in Japan, and much less so in the United States, which sort of, continued my, sort of, outside status I mentioned, even in... in chemical priorities. Namely, natural products of chemistry means to identify the chemical structure of chemicals in natural products, and that was the first priority, and the next one was what could you use them for, or why are they there, and then finally, even how are they synthesised by that plant or animal? Most of them were plants at that time.

The analogy is that you walk into a pitch-dark room, a furnished room, and you want to find out what is in this room, and by that I mean what sort of furniture, and initially, just are there tables, beds, chairs, what are they made out of, what are their shapes, what are their colours, and so on and so forth? And in the end, how are they made, why are they made, why is that there, assuming that you don’t even know what a chair is, and a table? Now, how would you do that if you go in a pitch-dark room and you have nothing? All you can do is grope around and you feel with your fingers, and sometimes you can be grossly misled, and sometimes you wouldn’t be. This is a good example, this table here, which is oval. Well, you know, when you feel it around you would not necessarily think that this is actually a table, and even the material is an unusual material for a table. This happens to be metal.  Most dining room tables are not really metal like this, and it wouldn’t feel that way, so you could already be misled if you just did it by feeling, although eventually you might be able to figure it out. Well, the next thing you do is you try and at least light a match, and when you light a match you can really illuminate only very little, and for only a very short period of time, so you have to either light a lot of matches and do it gradually, and then discover it, or maybe if you are lucky you can try and get a candle, and then you can see more, and maybe a flashlight, and so on. Now, of course the ideal thing would be if you take a photograph, and in fact, if you take a colour photograph then you’ve got everything there. With one photograph with a wide-angle lens you take the entire room, you see it right there, and you even see it in colour, and then you can already extrapolate very much what the materials are, although not necessarily entirely so.

Well that’s exactly what natural products chemistry is. You want to know what is in that particular plant, let us say, but how do you do that? The chemical structures are very complex ones, and many of them... in fact, that’s the interesting part, are unprecedented ones. So the idea would be to see pieces of furniture that you have not the foggiest idea what they’re really being used for, then you also have to figure out what they might be used for, and then, even when you’ve figured it out... why on earth did this plant, or this bacterium, because this is true, for instance, with antibiotics, would do this extremely weird chemistry, and how do they do this chemistry, which is so damn complicated, so much more complicated than anything we would do, and here is this little miserable bacterium doing all this, and how are they doing this? That is what natural products chemistry is, and from that standpoint it’s very different from synthesis, and in my... at that time, much more difficult. Because synthesis meant you know what you’re synthesising. In this case the house, where the house is a chemical... has a structure. Well, the architect who designed whatever it is, a roof, windows, well the chemist does it with chemical formulas. You saw what the steroid looked like, and then he could take a steroid that had never been synthesised, one he knew that has... it does have this... this ring system that you see here, but you know, you’ll add things here or there. Over here things that have never been made, but still, you know what it looks like immediately. Then you have to work out ways of doing it, so all you have to do is then work out building ways of constructing something that’s never been constructed before. Maybe you’re the first one to develop an arch, or a different... or use materials that hadn’t been used before. I don’t know, bamboo, or plastic, instead of wood or concrete, but nevertheless it’s there, you have precedent, it is not completely de novo. In the context of a natural products synthesis, in other words structure elucidation, rather than structured synthesis, it is diametrically the opposite, and I’ve found it intellectually so much more challenging that I became a natural products chemist, and therefore worked on many new alkaloids, and antibiotics, and terpenoids, etc, etc.

Austrian-American Carl Djerassi (1923-2015) was best known for his work on the synthesis of the steroid cortisone and then of a progesterone derivative that was the basis of the first contraceptive pill. He wrote a number of books, plays and poems, in the process inventing a new genre, 'science-in-fiction', illustrated by the novel 'Cantor's Dilemma' which explores ethics in science.

Listeners: Tamara Tracz

Tamara Tracz is a writer and filmmaker based in London.

Tags: Mexico, Mescaline, peyote buttons, Triterpenes, terpenoid, alkaloids

Duration: 7 minutes, 17 seconds

Date story recorded: September 2005

Date story went live: 24 January 2008