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Hisashi Yamamoto’s presentation on Thursday, October 29 was pretty easy to follow and understandable. Professor Yamamoto is apparently a very famous organic chemist and is a professor at the University of Chicago. He is Japanese, and since he was foreign-born and received his BS from Kyoto University in Japan, I think he still has some accent when he speaks english. However, I did not have any trouble understanding him.

Three new ‘things’ I learned include that 1) cascade reaction is ‘one-pot’ reaction, which synthesizes the complex multinuclear molecules from a single precursor, 2) discovering no side product reaction is important in cascade reaction, because it interferes with the next reaction (goal is to discover 100% atom efficient reaction), and 3) in cascade reactions, various amounts of substrates can produce different products.

Two questions I had during the seminar were 1) How long did you work on this catalyst research for? and 2) How do you figure out which reagent/s to use for the cascade reactions? For the second question, he answered that looking at the previous researches on cascade reactions and knowing the reactivities of each reagents, he can expect which product will be achieved.

I thought the presentation was interesting, because I like organic chemistry the most compared to other science classes, and Professor Yamamoto’s presentation was presented in such a way that undergraduate science major students can easily understand and be interested in his presentation.

I would describe the presentation in one short sentence so my ‘non-science’ friend or family could understand it as this way: “Interesting presentation by the world-famous organic chemist, Professor Yamamoto’s presentation was about cascade reactions.”

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Hisashu Yamamoto, currently Professor of Chemistry at the University of Chicago, is the most influential chemist I have seen in person.  Even as a young man Yamamoto has never wanted to do anything other than Chemistry,  in fact he  had read several university chemistry textbooks before graduating from high school! He has since then dedicated his career to organic chemistry and has seen the proliferate results of his dedication to the field. I could write my entire blog on his accomplishments and still not have covered them all; however, what I was most impressed with was his humbleness, not once did he seem to boast about his achievements or treat us in a way that made us seem less important than his other lecture audiences. I am not a big fan of clichés but the only way to truly describe his presentation style is by the three C’s: cool, calm, and collected.

Yamamoto’s presentation was about designing asymmetric catalysis that would be utilized in a cascade reaction for polyketide synthesis.  The transition from multiple step reactions to cascade ones are becoming more and more evident in organic chemistry.  Although there are some disadvantages, such as losing as much as 50% of the materials to waste, the efficiency of moving from a 15-20 step process, which could take over a month, to synthesis just one molecule,verses one day, by far outweighs the negative aspects of the experiment.  Not only are cascade reactions efficient, but they are (everyone’s favorite) cost effective as well. Imagine how much cheaper drugs could be if they were all done in cascade reaction.  I’m sure the pharmaceutical industry has taken note of this and it probably won’t be long before all the synthetic organic chemists will be shifting from condensing reactions to 2 or 3 step reactions to pot reactions if they haven’t already.  All in all, it is evident that cascade reactions are “green” (what every government wants to hear) and are clearly the future of organic chemistry; so I am certain new discoveries with plenty of funding are coming our way.

I learned many things from Yamamoto’s presentation, however a few concept that stick out in my mind are that 1% of polyketides have biological activity, 5x the average for natural products! That acids discovered over 150 years ago for experiments are still being used today, and the importance that super Bronstead  acids play in chemistry today. If I could go back, I’d ask professor Yamamoto where he sees cascade reactions bringing us in 20 years. And then I wonder when one pot reactions do become dominate, if they will decrease the demand for chemists and lab assistants as they could probably be loaded by a machine; thus I guess the question is,  will we eliminate the need for ourselves? This is not to say chemists won’t be needed, but just how many will be?  Only time will tell, and hopefully Jesus will come before then!

Thanks Dr. Yamamoto for visiting us at Andrews University!

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This week’s speaker was Hisashi Yamamoto, from the University of Chicago.  Dr. Murray met Yamamoto at the symposium in Paris last summer.  Yamamoto is known as a world famous organic chemist.  His presentation was on designing asymmetric catalysis for polyketide synthesis.  Cascade, or “one-pot” reactions are used to make polyketides.  Cascade reactions have been known to reduce the number of steps that a reaction requires, saving both time and material.  These reactions also give no side products and are 100% atom efficient.  Only 1% of polyketides are biologically active and require more than 50 steps to make.

The Mukaiyama aldol reaction is an important reaction for polyketide synthesis.  Very strong acid catalysts, called super Bronsted acids, were needed for this reaction to work.  Triflimide can create an immortal catalyst system.  Chiral phosphoric acid catalysts were investigated.  Acids with selenium were more acidic than acids with sulfur or oxygen.  If the acid catalyst is strong enough, the reaction can be done in water.

A super silyl (TTMSS) group needed to be used in place of a silyl (TMS) group.  Super silyl groups are protecting groups.  They provide a great steric effect, but since they have high HOMO levels, they are also very reactive.  Super silyl makes enolates and cations more reactive, and it provides sufficient reactivity of silyl enol ether.  When super silyl groups react with aldehyde, aldols are produced.  The number of aldols produced depends on the equivalents of super silyl used.  Super silyl provides for very high diastereoselectivity and high yield.  The selectivity tends to be of the syn configuration.  To change the stereochemistry of the product, the stereochemistry of the super silyl group needs to be changed.

Yamamoto’s presentation was heavy on organic chemistry content, and he received a lot of questions at the end.  Yamamoto answered those questions well.  However, the presentation was uninteresting for me.  I had difficulty seeing how all the different reactions came together.  I also did not understand what polyketides could be used for.  If someone is going through all of these organic reactions to make a polyketide, I want to know the purpose of the polyketide.  If only 1% of polyketides are biologically active, what biological activity do the polyketides carry out?  I would also like to know what is meant by “immortal catalyst system.”  It is a term I have never heard before.

Finally, I would like to know if super Bronsted acids are useful in other organic reactions besides the Mukaiyama aldol reaction.  The presentation was difficult to understand at times, but any organic chemist would have loved Yamamoto’s presentation.  If I had to sum up the presentation for a layperson, I would say that polyketides were being made using economical and fast reactions.

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