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School of Chemistry and Biochemistry
School of Chemistry and Biochemistry
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ItemA Study into the Design, Synthesis, and Application of Asymmetric Catalyst Systems(Georgia Institute of Technology, 2023-04-17) Benda, MeghanThe importance of asymmetry, or chirality, in the natural world cannot be overstated and its role has been extensively studied in the fields of chemistry, biology, physics, materials and more. As a result, researchers have dedicated immense time, resources, and funding to the development of chiral resolution and asymmetric induction techniques. In this thesis, we focus on the design, synthesis, and applications of asymmetric catalyst systems. First, in a demonstration of the utility of asymmetric catalysis in the production of medicinally relevant materials, we disclose the total synthesis of three 7-keto-9-hydroxy-8,4’-oxyneolignans in up to >99% ee featuring a key Sharpless asymmetric dihydroxylation step. Additionally, we disclose the synthesis and reactivity of a pair of C2-symmetric thiophene-fused cyclopentadienyl ferrocenes. Finally, the attempted formation of a binaphthyl-based chiral calcium disulfonimide complex is discussed including its observed reactivity toward ring-opening cyclizations.
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ItemLeveraging The Reactivity Of 1,3-Dipoles To Access Heterocycles And Carbocycles(Georgia Institute of Technology, 2022-09-07) Chen, DorisHeterocycles and carbocycles often exhibit remarkable structural features as well as propitious bioactivities that attract immense attention from the synthetic community. These motifs also constitute the core framework of many natural products and synthetic pharmaceuticals. For these reasons, a great need exists for the exploration and development of robust synthetic protocols that efficiently access these frameworks. In this thesis, heterocycles and carbocycles will be accessed in unprecedented ways by leveraging the reactivity of 1,3-dipoles, specifically in the form of N-alkoxyazomethine ylides and oxyallyl cations. Projects in all three realms of organic synthesis research will be discussed: (1) exploratory chemistry/methodology discovery, (2) methodology development, (3) target-oriented synthesis. First, in collaboration with Pfizer Inc., an exploratory project was initiated to study the generation and reactivity of novel N-alkoxyazomethine ylides in cycloaddition reactions to render nitrogen-containing heterocycles. In the second project, the first intramolecular, interrupted, formal homo-Nazarov cyclization methodology was developed. The method’s intramolecular oxyallyl cation trapping ability allowed facile access to complex (hetero)aryl-fused polycycles and led to a concise total synthesis of an antibacterial natural product, (±)-1-oxoferruginol. Third, in a target-oriented synthesis project, the progress made toward a key fragment in the total synthesis of an anticancer natural product, propolisbenzofuran B, using a homo-Nazarov cyclization approach, will be recounted.
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ItemLeveraging C-X Bonds for Triggered Eliminations, Alkene Functionalizations, and Intramolecular Cyclizations(Georgia Institute of Technology, 2022-05-02) Jones, ElizabethChemists continue to take inspiration from nature when it comes to finding and creating biologically relevant compounds. Two branches of organic synthesis—methodological development and target-oriented syntheses—serve different functions towards the same goal in medicinally chemistry. Probing new chemical space by way of developing novel synthetic methods to heterocyclic compounds is one of two foci of this work. In partnership with Pfizer Inc, development of alkoxyazomethine ylide cycloaddition methods were explored and investigated in attempt to access complex pyrrolidine compounds of purely synthetic design. The second foci of this work sought to leverage known natural chemical processes and adapt them for synthetic replication. Marine sources of natural products continue to produce exceptionally unique compound scaffolds, with demonstrated activities against a wide array of microorganisms. One such class of compounds is the macrolide compound family isolated for the macroalgae Callophycus serratus. With no current total syntheses completed to-date however, there is no efficient way to access these compounds in a cost-effective manner. To aid in this venture, novel methods were developed to key structural components of these macrolide compounds, in addition to other synthetic-focused methodology and reaction discovery.
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ItemExploration of copper-catalyzed Grignard cross-coupling between 3-halo-4-alkoxybenzoates and bromoisoprenoids(Georgia Institute of Technology, 2022-05) Lutin, David J.Allylic functionality, often taking the form of terpenes, is a mainstay of marine natural products. The aryl-allyl connection is particularly common, appearing in several product classes derived from Callophycus serratus, many of which exhibit promising initial biological activities. In pursuit of several total syntheses, which leverage a copper-catalyzed Grignard cross-coupling between a 3-halo-4-alkoxybenzoate and geranylgeranyl bromide, we explored the effects of alkoxybenzoate and halogen substitutions on the coupling. By scrutinizing the constraints and influences of these protecting groups on cross-coupling success, we lay out the potential for downstream deprotection chemistry. Here, we present the results of this investigation, along with a theoretical basis for the observations.
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ItemSynthetic Strategies Toward Heterocyclic Seven Membered Ring Systems: Building Libraries of Privileged Scaffolds for Medicinal Chemistry and Forensic Analysis(Georgia Institute of Technology, 2021-12-14) Parker, Ariel N.Natural products are often the inspiration for many pharmaceutical compounds as they are found to have drug-like properties. Many times, these compounds exhibit structural commonalities and are therefore referred to as “privileged structures.” Synthetic organic chemists have devoted significant time and effort into developing efficient methods to access these privileged scaffolds for the construction of diverse libraries. This thesis explores novel synthetic strategies to access the privileged scaffolds: cyclohepta[b]indole and the 1,4-benzodiazepine, flubromazepam. The protocols designed to access these heterocyclic seven-membered ring systems include: 1) a formal [5+2] cycloaddition between alkenes and indole fused alkylidenes, 2) a Friedel-Crafts transformation and 3) a nucleophilic arylation. Additionally, through the development of these modular protocols new discoveries were made providing new insights in medicinal chemistry and forensic analysis.
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ItemUnprotected Carbohydrate Conversion to Polyhydroxyalkyl Furans and Dihydrofurans: Improvement, Expansion, and Interruption of the Garcia Gonzalez Reaction via Homogeneous and Heterogeneous Catalysis(Georgia Institute of Technology, 2021-11-18) Ronaghi, NimaBiomass conversion of carbohydrates will lay the foundation for the future of materials, chemicals, and fuels. The Garcia Gonzalez reaction, an undervalued reaction coupling carbon nucleophiles with aldose sugars, can be an integral part of the carbohydrate conversion world, given the high yields, ease of tunability, mild conditions, and ease of setup. The improvement of the homogeneous catalysis of the Garcia Gonzalez reaction, using zirconium chloride as the catalyst, allows for more mild, facile synthesis of polyhydroxyalkyl and C-glycosyl furans. The expansion of the catalysts to a well-defined metal-organic framework, specifically UiO-66, showcases an example of heterogenizing a catalyst for a reaction system, as well as tuning the catalytic and morphological properties. Finally, interruption of the Garcia Gonzalez reaction is displayed by accessing a polyhydroxyalkyl dihydrofuran, rather than the polyhydroxyalkyl furans synthesized in the previous chapters, by using a cheap, recyclable magnesium oxide catalyst.
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ItemSynthesis of Degradable Monomers for Ring-Opening Metathesis Polymerization(Georgia Institute of Technology, 2020-05) Crolais, Alex E.Ring opening metathesis polymerization (ROMP) is a type of olefin metathesis chain-growth polymerization that has shown great versatility in the field of polymer chemistry. Although it allows polymerization of monomers containing a variety of functional groups, how effective it is in polymerizing degradable monomers is largely unknown. In this report, we demonstrate a novel synthetic pathway to synthesize an acetal-containing degradable monomer that is compatible with ROMP and the Grubbs 3 (G3) catalyst. Polymers made from this monomer were characterized by GPC analysis and underwent degradation studies. Acetals generally undergo hydrolysis in mildly acid conditions and even in biologically relevant pH ranges, so this new monomer will have potential applications in drug delivery systems. The monomer also has the capacity to have its functional groups modified, changing its functionality which will be further studied.