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Conformational Communication Through Ortho-Phenylene Oligomers

Devkota, Govinda Prasad
http://orcid.org/0000-0003-3480-2055
http://rave.ohiolink.edu/etdc/view?acc_num=miami1689289338091259

Abstract Details

2023, Doctor of Philosophy, Miami University, Chemistry and Biochemistry.
Mimicking the structure and properties of the natural biomacromolecules, such as proteins, nucleic acids, and polysaccharides, by developing new synthetic oligomers could offer valuable tools for the life sciences. ortho-Phenylenes are simple aromatic foldamers that fold into compact helical conformations because of arene-arene stacking interactions. This dissertation examines the connection between conformational behavior and chiral induction present in o-phenylene oligomers and discusses how this can be used to communicate chiral information over distances through foldamers. Additionally, a new class of pyrazine-based oligomers is synthesized, and their conformational studies are discussed. Chapter 2 presents the detailed investigation of conformational control of o-phenylenes by attaching terminal amides. NMR spectroscopy, taking advantage of 19F labeling, allows multiple conformers to be detected for each compound. In combination with CD spectroscopy and DFT calculations, specific geometries corresponding to each conformer have been identified and quantified. Conformers differing in the orientation of the amides were distinguished, with N-out orientation favored, particularly for the amides that are less sterically demanding. The configuration of the terminal amide groups is effectively transmitted to the o-phenylene backbone, leading to preferential one-handed helicity. Chapter 3 investigates the phenomenon of long-range structural communication in ortho-phenylene foldamers. We synthesized hexa(o-phenylenes) and characterized their conformational behavior using NMR spectroscopy. To further expand our investigations, we synthesized (S)-oP10Ph(CHO) and (R)-oP10Ph(CHO) and attached (R)-(−)-1-cyclohexylethylamine at the binding site. The binding of chiral amine resulted in distinct conformations, namely out/in and in/in, for (S)-oP10Ph(CHO) and (R)-oP10Ph(CHO), respectively, suggesting potential communication between the chiral amide and imine groups, likely mediated by the foldamer’s helicity and manifested in the orientation of the imine. Ongoing research involves a comprehensive study integrating CD spectroscopy, NMR spectroscopy, and computational methods to gain a detailed understanding of the mechanisms underlying long-range communication in o-phenylene foldamers. In Chapter 4 we developed a new synthetic approach to synthesize a series of novel pyrazine oligomers and investigated their preliminary conformational behavior using a combination of 2D NMR. Despite encountering challenges in the synthesis of some oligomers, successful synthesis of phenyl-substituted pyrazine-based oligomers enabled further analysis of their folding properties. The NMR assignments reveal significant upfield shifts in the proton signals of inner rings, suggesting the presence of possible pyrazine ring stacking and the formation of an extended helix. Further research is ongoing to explore their folding behavior and conformational analysis.
Scott Hartley, Prof. (Advisor)
Dominik Konkolewicz, Prof. (Committee Chair)
Jessica Sparks, Prof. (Committee Member)
Benjamin Gung, Prof. (Committee Member)
David Tierney, Prof. (Committee Member)
452 p.
Organic Chemistry; Physical Chemistry
conformational analysis; folding; foldamers; ortho-phenylenes; fluorine NMR; long-range communication; chiral induction; pyrazine oligomers

Recommended Citations

Citations

  • Devkota, G. P. (2023). Conformational Communication Through Ortho-Phenylene Oligomers [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1689289338091259

    APA Style (7th edition)

  • Devkota, Govinda Prasad. Conformational Communication Through Ortho-Phenylene Oligomers. 2023. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1689289338091259.

    MLA Style (8th edition)

  • Devkota, Govinda Prasad. "Conformational Communication Through Ortho-Phenylene Oligomers." Doctoral dissertation, Miami University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=miami1689289338091259

    Chicago Manual of Style (17th edition)

miami1689289338091259
47
© 2023, some rights reserved.Creative Commons License Conformational Communication Through Ortho-Phenylene Oligomers by Govinda Prasad Devkota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Miami University and OhioLINK.