Kenso Soai and Joanne Thomson discuss the origin of chirality in life

Kenso Soai

Kenso Soai is professor of applied chemistry at Tokyo University of Science. His research interests centre on chirality in organic synthesis, including asymmetric autocatalysis and spontaneous asymmetric synthesis.

 

What first inspired you to become a chemist?

I have been interested in the natural sciences since my childhood. My hope was to become a researcher in this area, although I hadn't decided on a specific subject. After entering university, I attended various lectures and seminars to help me decide. In the middle of my second year, I chose chemistry as the major subject because I thought that I would be able to contribute the most to this subject.

Much of your work focuses on asymmetric autocatalysis. Could you explain what this is and why it is important in understanding the origin of homochirality in life?

Asymmetric autocatalysis is a reaction in which a chiral product acts as a chiral catalyst for its own production. Because the structures of the catalyst and product are the same, consecutive asymmetric autocatalyses using the product of one round as the catalyst for the next significantly amplify the enantiomeric excess (ee) from extremely low to near enantiopurity and also significantly increase the amount of product.

Living organisms use only L-amino acids and D-sugars. How this chirality originated and the method of enantioenrichment are questions of broad interest that are also related to the origin of life. Several theories have been proposed for the origin of chirality, but the ees induced by these mechanisms have been very low. Asymmetric autocatalysis could be the answer. An initial spontaneous fluctuation in the ratio of enantiomers could have led to asymmetric autocatalysis and the amplification of chirality in nature.

What else are you currently working on?

We are working on asymmetric induction in organic compounds by physical factors. We have found that quartz and circularly polarized light act as the origin of chirality to afford highly enantioenriched compounds. We have also demonstrated spontaneous absolute asymmetric synthesis, where enantioenrichment occurs without adding any chiral material. For example, the reaction between pyrimidine-5-carbaldehyde and diisopropylzinc, affords enantioenriched pyrimidyl alkanol product because the initial tiny enantiometric imbalance is amplified by asymmetric catalysis. Our dream is to induce chirality in compounds by these chiral physical factors.  

Asymmetric autocatalysis with amplification of enantiopurity is not a mere purification or separation of enantiomers but an increase in the amount by self-replication, one of the essential features of life.

What are the best parts of your job?

The best part is that I am really interested in the research I do. The moment when a promising result is obtained, especially if it is unexpected, is very stimulating.

Chemistry is a bridge combining people with the same interests and passions. Listening to the excellent lectures, discussions and collaborations about chirality with chemists all over the world makes my life really exciting. 

You have received numerous awards and honours during your career, including the Chirality Medal in 2005. What do you think is the secret to successful research?

I have been working on the enantioselective addition reaction of alkylmetal reagents to aldehydes using chiral ligands or catalysts to form enantioenriched sec-alcohols for nearly 30 years. We reported the first asymmetric autocatalysis in 1990, but it took us another 5 years to finally find asymmetric autocatalysis with amplification of enantiopurity. We kept at it because I thought it a very fascinating project. Persistence, therefore, may be one of the conditions necessary to obtain success.

What do you do in your spare time?

I usually go for a walk along the banks of my local river and read a book. I like to read books about history. Although at school we learned the history of heroes and politicians, we didn't learn much about the lives of normal people in ancient and medieval centuries. 

If you weren't a chemist, what would you be? 

When I was a student, I was attracted to scientific subjects such as biology, chemistry, mathematics and geology. If I weren't a chemist, I would most likely be a biologist.