ChemSemBlog

The seminar that was held on October 29, 2009 was  called “Designing Asymmetric Catalysis.” The speaker was Hisashi Yamamoto, from the University of Chicago. He is known as a world famous organic chemist. I was impressed that he always wanted to be a chemist; he started to read some university chemistry books when he was a high school student. Later, he graduated and received a bachelor degree at Kyoto University in Japan, and received a Ph.D. at Harvard University. Not only that, but also he has over five hundred original publications and many journal and review articles that have been published.

As mentioned before, his presentation was on designing Asymmetric Catalysis for polyketide synthesis.  In this synthesis, cascade reaction, the “one-pot” reactions is used. Due to cascade reactions, the number of steps in the reaction decreases which also lead to save time and materials for the experiment. Additionally, it does not give side products and it would cause interference in reaction.

I learned new things in this seminar. First, only 1% of polyketides have biological activity and require more than fifty steps to synthesize. Second, different amount of substrate can produce different products. Third, cascade reaction is no side product reaction, giving 100% atom economy.

I also had two questions, first, how long he has been working on this research?  Secondly, what other things would be on 99% of polyketides? However, for the second question, his answer was that 99% of polyketides are selective.

Overall, the topic of this seminar was interesting and it was pleasure to meet a world famous chemist. He was really nice and kind when answering questions. If I can sum up this presentation in one sentence, it would be that cascade reactions can decrease steps in synthesis, which is really beneficial in saving time and materials.

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This week’s seminar was Designing Asymmetric Catalysis: Cascade Reaction for Polyketide Synthesis.  The speaker was Hisashi Yamamoto, an organic chemist, who received his BSc from Kyoto University and PhD from Harvard.  He has held many teaching positions over the years, such as Assistant Professor and lecturer at Kyoto University, Associate Professor of Chemistry at the University of Hawaii, Professor at Nagoya University, and an Arthur Holly Compton Distinguished Service Professor at the University of Chicago.  He has also received many awards over the years.  The presentation was interesting and easy to follow.

One of the new things I learned in this seminar was that when looking at a catalyst it is important not to have any side product and it needs to be highly reactive.  The speaker liked super bronsted acid.  And a small amount of base can kill an acid catalyst reaction.

The other students seemed to be pretty attentive during the seminar and the question and answer period went very well, the presenter was very knowledgeable about his topic.

The presentation definitely encouraged me to learn more about the subject.  However I do not think I would be interested in doing research on it.

I think the reason that this seminar was interesting was because it seemed to have a lot of practical applications. If I had do describe this seminar in one sentence it would be, “world famous organic chemist, Professor Yamamoto presents ways to speed up organic reactions.”

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This presentation was done by a world famous organic chemist, Hiashi Yamamoto. Yamamoto had a mild Japanese accent and soft spoken, but his presentation was very understandable, in which he explained a lot. His current interests are cascade reactions for polyketide synthesis. I found this topic to be interesting and it was amazing that Yamamoto made up some of his own catalysts as well as reactions, such as the super bronsted acid, and the Sakuri reaction. Yamamoto started his presentation by giving a background of acid catalyst and telling of what he wanted to improve. His goal was to modify the acid making it more powerful, selective, and useful.

With the cascade reaction, they used a 1-pot reaction, in which a reactant is subjected to successive chemical reactions in just one reactor. The importance of polyketides are that 1% of them are biologically active, which is five times the average for natural products. Another interesting point was the Mukaiyama Aldol reaction, which can be key for the synthesis of Nyastatin A., Leucascandrolide A, and Tetrafibricin. These methods are three to four steps and were improved by changing the acid catalyst to a super bronsted acid or silyl acid, which are very strong. Yamamoto and his group also performed an excess aldol reaction to see if they can form molecules with large molecular weights. They found that they could make a trialdol, using an iodine benzene complex. This molecule has three chiral centers, making it possible to generate eight stereoisomers of one product. They also performed a sequential reaction from acid to basic in a one pot reaction which I thought was very interesting.

At the end of this presentation many questions were asked, and Yamamoto answered them well. Some students seemed to enjoy the presentation, while others looked as if it was tedious towards the end. I felt that the overall presentation was appealing and I learned a lot about cascade reactions.

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Dr. Hisashi Yamamoto was able to give a rather fascinating presentation this past Thursday in his work with acid catalysts for cascade reactions. I found myself a little bit more hyped up than usual for the seminar this past Thursday particularly from reading his flyer which highlighted his many awards, publications, and patents. Coming into the seminar with pretty high expectations, I was not disappointed at all as he was able to give a captivating presentation that was both easily comprehensible and full of interesting chemistry.

I was able to learn several things during this lecture which were new to me. This idea of using Super Bronsted Acids and the benefits of them seemed really innovative, and it made me understand why Dr. Yamamoto was such a great chemist. No side products and very low catalyst load brought considerable benefits to the synthesis of complex molecules like polyketides. He was able to use one pot, while drastically cutting down the synthesis time. Other interesting things that I was able to get from this presentations were that since only a very small amount of catalyst was used, sequential basic reactions are able to be done in one pot. For example, a Grignard reaction was able to be done in the same pot.

Despite a softer speaking voice than past lecturers, Yamamoto was still able to take command of the audience’s attention. This was probably accomplished from the understandable and exciting research that he presented. He was able to answer the questions we had for him, and I was able to get more information from the questions asked as well. For example ,I found that their was Super Bronsted Bases, and that the acids were actually made from a battery making company. If I were to explain this presentation to a non-science friend, I would say that it was to use stronger acid catalysts which ultimately led to one pot and faster synthesis of complex molecules.

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