Studies on Oximidine II - Total Synthesis by an Unprecedented Reductive Coupling
Issue Date
2009-10-20Author
Schneider, Christopher Mark
Publisher
University of Kansas
Format
323 pages
Type
Dissertation
Degree Level
Ph.D.
Discipline
Medicinal Chemistry
Rights
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
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The benzolactone enamide natural products are identified by three structural characteristics: a salicylate arene, a 12- or 15-membered macrolactone, and an enamide side chain. These natural products exert their biological activity by inhibiting the vacuolar-(H+)-ATPase (V-ATPase) enzyme. The benzolactone enamide oximidine II has been synthesized twice previously with only moderate yields realized for the key macrocyclization step. Following a previous Georg group strategy, we envisioned performing the ring-closure using a Castro-Stephens reaction. While optimizing this copper-mediated macrocyclization, we discovered an unprecedented copper-mediated reductive coupling reaction. The enamide side chain of these natural products is postulated to be critical for biological activity. To probe the importance of this acid-sensitive moiety, we synthesized an allylic amide homolog of oximidine II and tested both oximidine II and this analog in melanoma cancer cells. The bacterial enzyme UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) catalyzes the first committed step of cell wall biosynthesis. Using highthroughput screening, 5 scaffolds were identified with MurA inhibitory activity. Analog development of the pyrrole-benzoic acid scaffold failed to generate compounds with improved potency. We then turned to structure-based drug design to investigate new MurA inhibitors. Using computer-modeling software, low molecular weight molecules were docked into various MurA crystal structures. Evaluation of these docking studies revealed 4 small molecules as potential leads for further optimization. Dioxins are environmental pollutants that cause a range of biological effects in a dose-dependent manner. The exact mechanism of action for dioxins is not fully understood. 2,3,7,8-Tetrachlorophenothiazine (TCPT) was designed to probe potential mechanisms of action and biological effects of dioxin analogs. Utilization of Buchwald-Hartwig coupling methodology produced TCPT in 37% yield. Preliminary biological testing of TCPT has shown favorable pharmacokinetic properties.
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