Studies towards the synthesis of bielschowskysin and total synthesis of darobactin A

The isolation of evermore complex natural products has been continuously inspiring chemists to achieve total syntheses of such targets, while pushing the frontiers of the field of organic synthesis. The intellectual challenges encountered in these endeavors have tested the limits of our current knowledge and resulted in development of novel methodologies, thereby providing significant advancements in the field. Moreover, total synthesis of natural products that have promising bioactivity has had great merit in identifying novel pharmacophores and leads, thereby directly impacting the field of medicinal chemistry. The first chapter of the dissertation describes our approach towards the total synthesis of beilschowskysin, a marine furanocembranoid diterpenoid with impressive antimalarial and cytotoxic activity. The daunting structure of this natural product has posed a great challenge for the synthetic community, making it one of the most intractable natural products ever discovered. While most of the past approaches towards this molecule relied on a [2+2] cycloaddition to form the strained core, our study was based on a different paradigm, accessing this unprecedented molecular framework via a Norrish-Yang photocyclization. Herein, we describe our successful synthesis of the macrocyclic precursor for the aforementioned photocyclization and further investigation of this key step. The second chapter will focus on our total synthesis of darobactin A, a bismacrocyclic heptapeptide, that was recently isolated from a bacterial symbiont of entomopathogenic nematodes. This natural product has shown remarkable antibacterial activity, selectively targeting gram-negative pathogens via a novel mechanism of action. We have developed a concise and convergent synthesis of this antibiotic, via sequential halogen-selective Larock indole syntheses.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Nesic, Marko

Contributors dc:contributor

• Sarlah, David
• Denmark, Scott E.
• Silverman, Scott K.
• Mitchell, Douglas A.

• Bielschowskysin
• Darobactin
• Total Synthesis
• Larock Indole Synthesis
• Macrocycle
• Macrocyclization

Statement dc:rights

• Copyright 2023 Marko Nesic

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/120220

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120220