Anna Schroeder

Multi-Step Synthesis of Small Molecules as Potential Inhibitors for MurG

April 9, 2021   /  

Name: Anna Schroeder
Major: Chemistry
Minor: French and Francophone Studies
Advisor: Dr. Sara Martin

The threat of antibiotic resistance demands a response in the form of new antibiotics that inhibit essential bacterial enzymes. A further requirement is methods for the synthesis of these inhibitors. MurG is an ideal target enzyme for this research as it is an essential enzyme in the synthesis pathway of peptidoglycan and no effective methods for inhibition have been found for this enzyme. Past computational models have found a potential inhibitor for MurG in coumarin-3-carboxamide analogues and previous work using Knoevenagel condensation reactions to synthesize these coumarins has produced contaminated product mixtures. The goal of this project is to develop a modified Knoevenagel condensation method in order to increase yield and product formation and make a small library of possible MurG inhibitors by synthesizing the analogues with a Q6S group. By heating the first part of the Knoevenagel condensation, three of the derivatives (1, 2, 3) were synthesized with increased yield and product formation while condensations to form three others (4, 5, 6) result in no product formation. Analogues 1, 2, and 3 were purified using column chromatography and then reacted with 2-oxo-1,2-dihydroquinoline-6-sulfonyl chloride (Q6S-Cl) to synthesize, via a nucleophilic reaction, a full inhibitor candidate (7, 8, or 9). 7 was successfully synthesized and purified while synthesis of 8 resulted in a contaminated product mixture due to the presence of an impurity, and 9 did not form. Future work on this project should include further purification to isolate 8 and further synthesis to form 9 and other compounds for the library, as well as testing full inhibitor candidates for inhibition of MurG.

Anna will be online to field comments on April 16:
10am-noon EDT (Asia: late evening, PST: 6-8am, Africa/Europe: late afternoon)

57 thoughts on “Multi-Step Synthesis of Small Molecules as Potential Inhibitors for MurG”

  1. Great talk! All NMR spectra are beautiful, but some of yours seem particularly challenging. How did you make peak assignments as to what might be your intended product vs. a mechanistic intermediate? (Also…Do I see some evidence of complex splitting in some of the aromatic signals?)

    1. Thank you Dr. Bonvallet! Yes, assigning peaks within these spectra was very challenging due to the presence of mechanistic intermediates (particularly products 2 and 8). I used NMR data from literature that featured similar coumarin products to determine the peaks for the intended product and tried to assign the rest of the peaks to an intermediate or impurity based off the mechanism or possible side reactions. The mechanistic impurity within the NMR of product 2 fit the most with the structural peaks present and it made sense mechanistically as it was a stable intermediate. Yes, there is definitely evidence of complex splitting within the aromatic region and I concluded that the doublet of doblet was the result of effects from the ortho and meta protons.

  2. Congratulations, Anna! I enjoyed mentoring you through this project and seeing your growth from the beginning of the project until now. What was your biggest takeaway from the IS experience (outside of the conclusions from your experiments)?

    1. Thank you Dr. Martin! I appreciate your mentorship and all the assistance you provided me throughout this project. My biggest takeaway from the IS experience is the flexible and goal-oriented mindset needed in order to complete a project independently. In the past, when I was in a group, I was able to rely on my fellow researchers for guidance and ideas, but now I had to make these decisions myself and make sure I wasn’t getting stuck in a direction that wasn’t generating the answers I hoped for.

  3. Great work and congratulations Anna! How have your experiences in IS and past research shaped your goals / focus as you look towards starting graduate school?

    1. Thank you Dr. Sobeck! My past research and IS experience have taught me that I really love lab-based research and I would love to continue applying my skills in synthetic organic chemsitry to projects with practical applications. I also discovered that I really like having a project that works at the interface of different fields (biochemistry and synthetic organic chemistry as for this project) which is why I am really excited about going to UD for graduate school since they really encourage this kind of research.

  4. Great job Anna, we are so proud of you. I know first hand how challenging a chemistry I.S. can be and I can’t even imagine how tough it was this year with the pandemic limitations. We are excited for you as you complete your undergraduate time and start grad school. I don’t have any questions (since you don’t have any IR data!) but you can show me those later. Enjoy these last few weeks on campus.

    1. Thank you Mom! This year was challenging with the pandemic but also really rewarding. I will show you the IR data later!

  5. Anna , congratulations on passing your IS and a great talk! Also, congratulations on admission to graduate school. Keep up the good work!

  6. Nice job, Anna! If you could go back and give advice to your Junior IS self, what would it be?

    1. Thank you Dr. Morris! I would tell my Junior IS self not to be so disheartened by not forming a product on the first try because it is just a part of the process of synthetic projects. I would also tell myself that it is okay not to reach all the lofty goals I wanted to accomplish in my Junior IS proposal.

  7. Congratulations on completing I.S., Anna! It is clear that you are thorough and confident about your research. You are doing to do great things in graduate school!

  8. Exquisite work Anna, very nice! Would you be able to give a layman’s explanation for why some substances may end up with an impurity and others do not? Is it the case that the process of synthesizing a substance is not entirely precise, so you may end up with something other than only what you’re looking for?

    1. Thank you Max! In the case of product 2, I believe the presence of the mechanistic intermediate was due to there not being enough hydrochloric acid in the second step to react with the intermediate resulting in a contaminated product mixture. It may also be the case that the mixing conditions were not good enough to allow the hydrochloric acid to reach the the intermediate and form product 2. The problem with batch reactions (which is what I used in these reactions) is that there is always a chance the starting material and intermediates will interact with something else and result in the formation of undesired side products. It is also possible (in the case of 4, 5, and 6) that other parts of the starting material (the substituent groups) will affect the ability of the molecule to react.

  9. Anna,
    Nice work! I am an alum (’81) and chair of Chemistry and Biocchemistry at La Salle University in Philadelphia. NMR interpretations are difficult and your thoughts of running COSY and HSQC spectra are a great idea to establish connectivity. It’s great to see this level of work coming out of Wooster. My best to you in the future.

    1. Thank you! I am hopeful that others in the future will consider using these advanced NMR techniques to establish NMR peak assignments definitively. Glad you enjoyed the presentation!

  10. Fantastic job, Anna! I thoroughly enjoyed your presentation; it was fairly easy to follow, even as a non-STEM major, so thank you! It sounds like your research will be integral to the future inhibition of MurG and the development of potentially groundbreaking antibiotics, which is phenomenal! Congratulations!

    1. Thank you Dante! I’m glad you were able to follow the presentation and that you enjoyed it. I am hopeful that this work will assist in the discovery of an inhibitor for MurG but there are still many steps to go before a new antibiotic is made!

      1. You’re welcome! Yes, that makes sense. In any case (and with my limited knowledge), your work is sure to be a worthwhile and significant contribution!

    1. I would advise them to continue applying modifications to the Knoevenagel condensation in order to synthesize the rest of the coumarin derivatives but to not be afraid to try a different reaction if they think it will work better. I would also advise more aggressive purification of coumarin derivatives before using them in further synthesis so they don’t have contaminated product mixtures and crazy NMR. They should also know that a few failed experiments does not mean your project is over. Focus on the successful reactions and go from there.

      1. Congratulations! What an impressive presentation. Grandpa actually understood quite a lot of it. You can explain to me in a simpler way as I don’t have any background in chemistry. We are so proud of you. That’s a great picture of you. Love, Grandma and Grandpa

        1. Thank you Grandma and Grandpa! I promise I will explain the project to you more fully in the future.

    1. Thank you Maya! I will be attending the University of Delaware for graduate school next year where I hope to get a PhD in organic chemistry.

  11. Congratulations, Anna! After hearing anecdotes about your research journey over the last few months, it’s wonderful to see the results and hear more of what you have been studying. Fantastic work, especially with making the project accessible to non-STEM majors!

    1. Thank you Claire! I’m glad you enjoyed the presentation and understood what was going on! Thanks for putting up with my complaints about the NMR and rotary evaporator.

  12. Congratulations, Anna! It’s so good to see all that time you spent in the lab paying off! Thank you for sharing your research as well as making it accessible! I look forward to seeing what else you accomplish.

  13. Anna, this is beyond amazing! I can’t imagine how much time you had to devote to this, but it’s really paid off. CONGRATS!! You are incredible!

  14. I can not speak to the content of the presentation, but the diction and articulation of the concept was very well done! Great job making complex scientific concepts accessible to non-STEM people. Congrats with all you have achieved recently, but I am NOT at all surprised by your success.

    1. Thank you Karin! I am glad you were able to understand the presentation to a degree.

  15. Congratulations and félicitations Anna!!! This was a great presentation, and I loved getting to see your work and learn a little more about what you’re doing when you’re in the lab!

  16. Really well done, Anna! It’s evident how much time and thought you’ve put into this (and blood, sweat, and tears) and congratulations for coming out on the other end intact!

  17. Thanks, Anna, for your presentation, and for contributing this way to improving antibiotics. It sounds like you’re building on research other students have done in the past? Is that right? How do you see yourself balancing independent and team work in graduate school and beyond?

    1. Thank you Mrs. Vosmeier! Yes, I was continuing the work done by past students within the Martin lab in synthesizing the desired inhibitor and I hope future students will continue my work by building a bigger library of possible inhibitors to test on MurG. I see myself using the skills I have learned in doing independent work to direct my personal goals in the lab setting while also using the communication and mentorship skills I have gained in doing group lab work when working with a team in graduate school.

  18. Fantastic presentation Anna! I’m very proud of you and everything you’ve accomplished. I know you will do amazing in graduate school

    1. Thank you Holly! I really appreciate the support and thanks again for being my safety buddy when I needed one!

  19. Anna, congratulations!! This was a great presentation and explained a complicated topic very well. It’s been so fun to hear about your IS project and process throughout the year, it was great to listen to your talk and hear the conclusions of it!

  20. Well done, Anna! The presentation seemed like an excellent summary of a challenging, but also rewarding experience. Thanks for sharing it!

    1. Thank you Dr. Feierabend! Thank you again for all the assistance on the computational work in my thesis.

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