 So, good morning, I will come back to the NPTEL course on Classics in Total Synthesis Part 1. So, in the last lecture we talked about Total Synthesis of Progesterone Sterite. So, we will continue our discussion today also on Total Synthesis of Sterites, particularly Progesterone, one more Total Synthesis as well as Synthesis of Cartesian and so on. In the last lecture, when I talked about Total Synthesis of Progesterone by W. S. Johnson, there we talked about a Domino Cation Triggered Cyclization and that was like Biomimetic Total Synthesis of Progesterone, that was a classic one and it was of academic interest. If the same strategy has to be applied for industrial production of Progesterone then it will be very, very expensive. So, for the industrial production of all these steroids, you need much, much better method and inexperiency method to synthesize, okay. So, today we will talk about a method where Progesterone, Cartisone, Testosterone always synthesize on a industrial scale and because of that it was inexpensive, okay. So, how? In today's lecture, I talk about synthesis of 3 steroids starting from a compound called Diasgenin, okay, this is called Diasgenin, I will come back to that what is Diasgenin and where from it was isolated and how it is used in its conversion to Progesterone, then Cartisone, then to Testosterone. As I mentioned during my introduction, when you are starting with a natural product like compound or material obtained from a natural product which has almost all the features of the target molecule, then conversion of this natural product or natural product like molecule to the target molecule, then the whole process is called Semi-Synthesis, is not it? So, here the synthesis which I am going to talk about starts with Diasgenin, okay. You can see that the Diasgenin has the core structure of the 3 steroids which we are going to discuss today, okay, Diasgenin has the core structure A, B, C, D rings, okay. All the 4 rings present in Progesterone, Cartisone and Testosterone are there. What is not required is the bicyclic system, the Spyroketal, okay. The Spyroketal is not required, okay. How to get rid of the Spyroketal and convert into the required side chain in Progesterone, Cartisone and Testosterone, okay. So, that is what we are going to discuss. But another interesting aspect about the synthesis which we are going to talk about is about industrial method, okay, how one can prepare in large quantity, okay. And we start with the discovery of Diasgenin. If you look at the history of steroids, okay, 1930s were the beginning of discovery of many major steroids. In fact, 1929 was the discovery year of female sex-carvone called Estro, okay. So from 1930s to 1980s, steroids played a very, very important role in pharmaceutical companies, okay. So many drug discovery program of steroids were focused during these 6 decades and that is why we call this as you know the 1930s was called as decade of the sex-carvone. But subsequently, in the next 50 years, lot of attention was given to synthesis of you know many, many steroids. Many structures of other steroids were discovered in the next few years, particularly the male sex-carvone Testosterone, female sex-carvone as I said was discovered in 1929 and little later the pregnancy hormone again related to females was, pergesterone was discovered or elucidated and later these were used as drugs, okay. But the isolation of these 3 steroids yielded very, very you know minute quantity of the natural product. So obviously if it has to be used as drugs, then it has to be synthesized prepared in large quantity, okay. So how this can be done? Already we talked about the totals in the supprogesterone by W. S. Johnson that came in 1950s, okay. But among these 3 steroids particularly the steroid called progesterone got much attention because this had very interesting medicinal properties in the treatment of menstrual disorders, okay. So this was a serious problem those days even now. So the progesterone used to be given as a drug of choice those days. So more synthetic efforts were on the synthesis of progesterone, okay. But unfortunately as I said the high cost, the high cost in the preparation or synthesis of this molecule restricted its use as a drug, okay. However in 1940s that the cost of progesterone fell dramatically, in 1940s the cost of progesterone fell dramatically. And that is because of the formation of a Mexican company and how that Mexican company was formed and again how it was started from the academic laboratory. Let us discuss in the next few slides. So the person called Russell Marker was responsible for the synthesis of progesterone from diasterein. So diasterein as I said is a naturally occurring compound. It was isolated from the plant steroid called sarsaparilla, okay. So Russell Marker was a professor from Penn State University and he was the one who correctly proposed the structure of diasterein and he did not stop there, okay. So what was his aim? His aim was as I mentioned since diasterein has the four rings present in all the steroids, his idea was can we convert this diasterein, okay, can we convert this diasterein into other steroids that was his primary aim. And how to do that, first you have to remove this side check, okay. The spiroketal, okay, the spiroketal should be removed. The spiroketal was considered as inert to various reaction conditions, okay. It was considered as inert to various reaction conditions. So but Marker thought he can really cleave that and then he used a very clever reaction which I will come to that little later to cleave this spiroketal, okay. To cleave the spiroketal once you cleave that then that opens the door for synthesis of several steroids, okay. In 1944, I think after 6 years after establishing the structure of diasterein, he first reported the really practical synthesis of progesterone, practical means it is possible and it can be sold at affordable price from diasterein, okay. That is very, very important. See when we talk about academic work, when we talk about industrial work, okay, these two are different extremes I would say, okay. One is for academic interests, other one you have to keep it in mind the whole process should be affordable, okay. It should be inexpensive and overall costing should be affordable, okay. So with that, this practical synthesis of progesterone from diasterein was one of the best synthesis reported for progesterone, okay. However, as I said he has to isolate diasterein from the plant called sarsaparilla, okay. So that actually he could not get enough of this diasterein from this plant steroid. So that actually makes the whole process little bit more expensive. So he thought it is better to look for different sources, okay, different sources to get diasterein. Of course if we can get another plant or any other plant which gives more of diasterein, then from diasterein he can convert into progesterone, okay. So with that next what he did, he sent few of his, you know, students, most of them are botanists, okay, most of them are botanists. So he asked them to search, go around South America, America, Mexico and then search for different plant source which will give more of diasterein, okay. That was his first job. And second thing is, his idea was once he makes progesterone and if the process is, you know, inexpensive, then he can make other famous drugs, the cartisone and testosterone, okay. So that was his idea. So idea is to develop a low cost process for progesterone and that depends on the isolation of diasterein in large quantity, okay. And meanwhile he was also searching and when he was going through a botanic textbook he found a picture of diasterein, okay, picture of a plant called diasterein and that was growing only in Mexico, okay. So he is a big professor in Penn State University, he saw that easily he could have sent one of his students to go to Mexico and get this plant. Similarly in that plant, the root of the plant has diasterein, okay and the root weighs about 100 kilos. Then you can imagine if he can get 100 kilos of this root of this plant, how much he can extract diasterein and from that how much he can make progesterone. So with all this calculation his antenna went up and from academician he became an entrepreneur, okay. He thought, okay it is better, he himself start this process. One day he went to Mexico, okay, you can imagine, he went to Mexico by bus, okay and he talked to few people and bought two big bags with large roots of this plant, okay, two large roots of this plant he returned by the same bus but those days you know it was not like now, he put this two big bags on the top of the bus and after he crossed the US border when he got down, already these two bags were stolen, okay, so that used to be common those days. However what he did, he did another interesting thing, he talked to a policeman and then somehow bribed and got 50 pound root, okay, so 150 pound root and with that he returned to Penn State University, okay. So he could easily isolate the diasterein in reasonably good yield, okay, then he thought, okay this is the best way to isolate diasterein, once he isolates diasterein in good quantities then he can go for the total synthesis of progesterone. So with this idea in mind he went to the company called Park Davis, okay, it was a very famous company and his other research program was funded by this company, so he went to them and then said he has developed a nice process for the synthesis of progesterone from diasterein. Now the diasterein is available from this particular plant and this particular plant is available in Mexico. So he wanted them to support financially so that he can develop this process and then make this in large quantity. Unfortunately, not only that company, he also approached other pharma companies, all of them refused to fund this project. It was surprising those days because those days the requirement for progesterone and other steroids were really very high and it was a big surprise that pharma companies refused to fund this particular project. But as I said, not only he was an academician, he was also an entrepreneur, he thought why we have to talk to companies, why not, he himself can do it, okay, so he became an entrepreneur as well as academician, so he thought he will do it himself. This time he went to Mexico but he was careful and what he did, he talked to a small local small scale extractor. So somebody who can do this job, he talked to that person first. Then he collected 10 tons of that root, okay, 10 tons you can imagine, okay. He gave this 10 tons to this local person and asked him, you extract this root with alcohol, okay, then remove the alcohol and give only the syrup, okay. That person agreed and it is like, you know, when you start a small industry what you do, you give certain percentage of share to that person, is not it? So what he did, when the alcohol was evaporated, he got syrup, one third of the syrup he gave it to that person who actually extracted. The remaining two-third he brought it to New York, okay, with this two-third he got 80 kilos of progesterone, with two-third of, you know, whatever syrup he brought to New York. He made 80 kilos of progesterone, then he sold one gram of progesterone for $80, one gram of progesterone for $80. Now you imagine, how much money he made, one gram cost $80, 80 kilos how much it is? That is the real, you know, entrepreneurship in him when he was an academician. So this is very important, not many academicians would like to become an entrepreneur but at the same time, this is a classical example when he realized that, you know, there is a possibility that he could be a successful entrepreneur, he moved ahead and took the risk and then he became a successful entrepreneur, okay, and he did not stop there. So he thought, okay, he could make 80 kilos for the sustained development, for the sustained development and sustained supply of progesterone, it is better to form a company, isn't it? Well, thinking about forming a company, where to form the company, because this is also very important whether you want to form a company in US or you want to form the company in Mexico. Always, you know, if you are an entrepreneur, you know very well, it is better to form a company where your raw materials are available, okay, from a chemical company's point of view, when logistics used to be a problem, it is always better to start a company where raw materials are available. So he decided immediately that he will form the company in Mexico. So he talked to two more N dynamic entrepreneurs from Mexico called Somlo and Lehmann, okay, then as usual, you know, they have to sign an agreement for profit sharing. So they signed an agreement, then they formed a company called Syntax, they formed a company called Syntax. So with this company, they started producing progesterone, okay, but when you form a company with more people, okay, there is always a risk of, you know, getting into some trouble, okay. So in 1944, Marker did not get along well with these two entrepreneurs, okay, there was always, you know, profit sharing problem, okay. Then he had to come out of the company, but before that, what he did, what Marker did, he saw that Syntax will take off very well. So he resigned from Penn State University, okay, academic position he resigned, academic position he resigned and moved to Syntax. He thought, no, Syntax will be a good option, you can sell and you can make a lot of profit, okay. And also in the process you can see, he could sell progesterone for $50, earlier he was selling progesterone for $80 per gram. Now since this company was formed in the place where the roots are available, so the raw material cost everything came down, so he could sell the progesterone for $50 per gram. But as I said, a year later there was a problem and profit sharing is, you know, has affected Marker and then he thought, okay, why, why to stick with the company. But interestingly, one should know, this is very common, at least this used to be very common until, you know, 10, 15 years ago in process division. Once you have the know-how, once you have the process of know-how, many people do not disclose, many people do not disclose how to carry out the reactions. Marker cleverly what he did, he used coding, he used coding, all the reagents. So his partners did not know which reagent he was using, which reaction he was doing. They only know, they only funded, they only know that he is responsible for the chemistry and they have funded and overall once they sell, they will share the profit. But they did not know the real chemistry, okay. When as I said when there was a profit sharing, Marker has to leave the company, when he left the company, he just took the process because he himself did all the chemistry. So others just could not repeat the process. So what Marker did, he went out and started another company called Botanica Max, okay. So he also got supply of, regular supply of the roots from others and with that he started a company Botanica Max and that company was, you know, supplying progesterone. And he remained in that company until retirement. Meanwhile, the other two entrepreneurs, okay, who started the company syntax along with Marker, so they saw the potential of this process, but they did not have a person like Marker. So what they did, they approached, they approached many people, many scientists who can think of this process, so by now they know what is the starting material, diazine. So they wanted to know somebody who can do the same process and then synthesize progesterone in large quantity. So they appointed a person called George Rosengranz, okay and who did a lot of, you know, optimization and revived the work and he could start making progesterone and that is how syntax was really, you know, again back to business in making progesterone. So not only that, this person, this chemist, he extended this work, okay, once he made the progesterone, the progesterone was converted into cortisone and testosterone, okay. And syntax later they also collaborated with a very famous chemist called Jarasi, was well known for mass spectrometry and then his work on steroid particularly or on oral contraceptive. So they collaborated with Carl Jarasi and Carl Jarasi was responsible for converting diazine into cortisone and cortisone to testosterone and so on, okay. That time before Carl Jarasi used this method to make cortisone, the Merck Company was taking about 36 steps to synthesize cortisone, okay. Cortisone is one of the, you know, famous steroids being used now but you can imagine if it has to take 36 steps to make cortisone then it will be very difficult for, you know, common people to buy this cortisone, okay. That is how this particular strategy was very, very important to make cortisone in affordable. Meanwhile the Ujjan Company made a major breakthrough, major breakthrough in oxidizing, oxidizing progesterone. See if you look at the progesterone and if you look at cortisone, you can see there is a hydroxyl group oxygenated at C ring, okay. The C ring hydroxylation was done by this microbiological process. So because of that, so you do not have to go through chemical process to introduce the hydroxyl group. So this microbiological process reduced significantly the number of steps involved in the conversion of progesterone to cortisone, okay. So now let us go to the chemistry, how Marker actually converted diastereone to progesterone and later progesterone to cortisone and testosterone. So this is diastereone and as I said the first step is the removal of the spiroketal side chain. So what he did, he reflects this diastereone in large quantity, one can do it in tons also in acetic anhydride at 200 degrees, okay. At 200 degrees, you reflects with acetic anhydride. This cleaves and you get, you can see, see this is acetic anhydride and then this lone pair and this becomes OAC and followed by a loss of proton, you get the corresponding enol ether, okay. Now if you treat with chromium trioxide, if you treat with chromium trioxide, this cleaves, okay. Oxygenation followed by cleavage of this double bond, one gets the acetyl group, okay. You can see this is what you need, this is what you need in progesterone and your free hydroxyl was also acetylated in the first step. Now what you need is you need to remove this long chain, okay, remove this long chain. So this can be done by treatment with acetic acid. So when you do acetic acid, so hydrolysis of this ester takes place followed by dehydration gives this comp, gives this comp, okay. Now this is a very important intermediate, this is a very, very important intermediate in steroids. This is called 16 DPA. What is 16 DPA? It is called 16 dehydrofragnenolone acetate. So this is a very important intermediate for synthesis of several steroids that was obtained from diasterein in 3 steps, okay, using simple reagents. Once you have 16 DPA, then one can selectively hydrogenate the CD double bond, okay. So once you do that, then you get the beta acetyl group, then hydrolysis, the acetate group is hydrolyzed with potassium hydroxide to get the corresponding OH. Now if you oxidize, not only the hydroxyl group gets oxidized, then the double bond also migrates, that is nothing but progesterone. So if you look at the whole process, basically in 6 steps, in 6 steps, one can convert diasterein to progesterone, all using very, very simple reagents, commercially available inexpensive reagents to make progesterone. That is how Marker used this method to make tons of progesterone, okay. Now how 16 DPA, which is the intermediate, okay, which is the intermediate in the synthesis of progesterone from diasterein to convert into cortisol, okay. This is 16 DPA, okay. First you make epoxide of this double bond, alpha, beta and saturated ketone. So if you treat with alkaline hydrogen peroxide, that will selectively epoxidize alpha, beta and saturated ketone. So you make the epoxide. It is a stereoselective epoxidation, the epoxide comes from the alpha side. Now if you treat with HBR, it opens up, so you get the tertiary alcohol and the beta bromide. Meanwhile, when you treat with acetic anhydride, the free hydroxyl group gets acetylated, okay. Having done that, next you treat with HI. So HI, you know, gives this bromide SN2 like displacement to give corresponding iodide and the noninical removes the iodide, okay. So what you have done basically, the epoxide you open and then you have done the reductive removal of the halide. Now as I said, you need to introduce a hydroxyl group here and also a hydroxyl group in the serine. So this is where the Merck's process, microbial hydroxylation took place at this position, very important transformation. So once you do that, it does two things. What are they? One, the hydroxylation here and hydroxylation here, two hydroxylation, okay. The dihydroxylation actually helped, okay, reducing lot of chemical waste. Now potassium hydroxide will hydrolyze the acetate to alcohol, then chromium trioxide will oxidize that alcohol as well as this secondary alcohol in serine to give ketone and also the double bond will migrate, so that is nothing but Cartesian. Again you see from 16 DPA to Cartesian in few steps and one of them is a microbial dihydroxylation, okay. That is the key step in the conversion of 16 DPA to Cartesian. Then the same 16 DPA was successfully used to convert into testosterone, male sex hormone. How? Same in 16 DPA. Now you treat with hydroxyl. So when you treat with hydroxylamine, you have a ketone and that will immediately form an oxide, okay. When you have an oxide, the next reaction which should come to your mind is Beckman rearrangement, okay. So Beckman rearrangement on treatment with para-toluene sulfonychloride and then acid, so you can see this will give you this corresponding amide, okay, corresponding amide. Once you have this amide, now this is enamide, is not it? This is enamide, that enamide can get hydrolyzed to give corresponding ketone, enamide gets hydrolyzed to the corresponding ketone. So now from here testosterone was done in two steps. First you hydrolyze the acetate to alcohol, then you oxidize, you see you get the corresponding eniome, the 5-ambered ketone reduced to alcohol, okay. So selectively one can reduce the 5-ambered ketone with sodium borohydride to get testosterone. So if you look at the whole process, the whole process dependent on markers degradation step. So marker cleverly used a 6-step process to convert diastenine which is available from roots of you know Mexican plant to make 16 DPA in 3 steps and in 6 steps he converted that diastenine into progesterone. From 16 DPA you can convert that into testosterone and cartisone, okay. So all this started with the clever use of oxidation of diastenine to 16 DPA, okay. So I will stop here, we will continue our discussion on synthesis of steroids in the next class. Thank you.