The soil bacterium Rhodococcus has a wide array of secondary metabolic pathways such as production of pigments, siderophores, and antibiotics that makes it an organism of interest for the production of novel natural products. Analysis of the genome sequence of Rhodococcus indicates the presence of 24 non-ribosomal peptide synthases and 7 polyketide synthases possibly involved in production of secondary metabolites. The use of a solid agar extraction method to screen soil isolates of Rhodococcus for compounds with inhibitory activity against other bacteria resulted in the discovery of a promising candidate molecule. The Rhodococcus strain KCHXC3, isolated from eastern Tennessee soil, produces a substance that inhibits the growth of several Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia and Gram-positive bacteria such as Micrococcus luteus and, Staphylococcus aureus. After bulk extraction of this compound with ethyl acetate from agar plates, the material was partially purified through different chromatography processes.

Chapter One presents an overview of phosphorus reagents for the carbon homologations of aldehydes and ketones leading to functionalized carbonyl derivatives. Select examples are provided to exemplify the utility of carbon homologation methodology in synthesis and asymmetric organocatalysis and in the total synthesis of natural products. The directing effect of acetals on regioselective ylide formation is explored in Chapter Two. Evidence is presented for ylide formation through a complex induced proximity effect with lithium bases under coordinating conditions. Moreover, four-carbon donors represent a limit for useful directed ylide formation with trialkylphosphine-derived Wittig salts in carbonyl homologation reactions. A facile approach to the synthesis of methyl vinyl ketones (MVKs), using acetonyl tripropylphosphoranes under mild conditions, is reported in Chapter Three. A library of diversely functionalized MVKs was synthesized as a demonstration of the scope and generality of the methodology. The application of MVKs as substrates for organocatalysis and as building blocks for useful polyketide intermediates is briefly highlighted. In Chapter Four, the two-carbon homologation methodology that was presented in the previous chapter is applied to the synthesis of the polyketide olivetol and a series of O-methyl derivatives. Cyclic diketone intermediates were aromatized with catalytic iodine and DMSO as a terminal oxidant. Modification of the solvent system allowed for the selective synthesis of mono- or dimethyl ethers of methyl olivetolate. The selectivity of this aromatization is further explored in the final chapter with more complex substrates. Chapter Five focuses on the synthesis of the meroterpene phytocannabinoids found in Cannabis sativa. A synthetic strategy involving the sequential condensation/[3+3]-annulation of citral with cyclic 1,3-diketones synthesized in the previous chapter. This afforded non-aromatic meroterpenes that were subjected to acid-mediated thermal rearrangement and catalytic oxidative aromatization. Evidence for chemoselectivity of the aromatization methodology was demonstrated and a synthesis of methyl cannabinolate is presented. / Thesis / Doctor of Philosophy (PhD) / Methodologies for the extension of aldehydes to functionalized olefins and their application to the synthesis of cannabinolic acid methyl ester are presented.

Geldanamycin possesses various biological activities as seen in the NCI 60 cell line panel (13 nM avg., 70 nM SKBr-3 cells). The predominant mode of action providing these unique results arises from the ability of geldanamycin (GA) to bind to the chaperone heat shock protein 90 (Hsp90). Despite its complicated functionality, the first total synthesis of GA was accomplished, which included two new reactions developed specifically to address the stereochemical features. The final step in the synthesis of GA was a demethylation-oxidation sequence to generate the desired para-quinone. This step could only be accomplished with HNO3/AcOH, producing GA in 5% yield. A GA model study, which closely resembled the aromatic core, was extensively investigated to solve this critical oxidation issue. A protected hydroquinone model compound was determined to be the optimum choice. Using Pd in the presence of air with a 1,4-hydroquinone provided the desired para-quinone quickly and nearly quantitatively in 98% yield. This study formulated the recipe of success for para-quinone formation of GA and future synthetic analogs. Asymmetric glycolate alkylation has been developed using phase-transfer-catalysis (PTC). Diphenylmethoxy-2,5-dimethoxyacetophenone with trifluorobenzyl cinchonidinium catalyst and cesium hydroxide provided alkylation products at —35 °C in high yield (80-99%) and with excellent enantioselectivity (up to 90% ee). Useful α-hydroxy products were obtained using bis-TMS peroxide Baeyer—Villiger conditions and selective transesterification. The intermediate aryl esters can be obtained with >99% ee after a single recrystallization. The newly developed PTC glycolate alkylation was applied to the asymmetric syntheses of ragaglitazar and kurasoin A. Ragaglitazar is a potent antihyperglycemic and lipid modulator, currently in phase II clinical trials. Kurasoin A is a relatively potent protein farnesyltransferase (PFTase) inhibitor with an IC50 value of 59.0 micromolar. PTC glycolate alkylation was optimized to provide 4-benzyloxy glycolate intermediates in excellent overall yield and with 96% ee after recrystallization. Ragaglitazar was then synthesized after considerable experimentation to provide the potent lipid modulator with yields and enantiopurity rivaling the best-known routes produced by industry standards. Kurasoin A was produced through an α-triethylsiloxy Weinreb amide to provide the highest overall yielding route to this PFTase inhibitor currently disclosed.

Acutumine is a tetracyclic alkaloid isolated from the Asian vine Menispermum dauricum with selective T-cell cytotoxicity and antiamnestic properties. We have developed a total synthetic route to this congested alkaloid, during which we also found a novel, stereoselective radical-crossover reaction that combines an intramolecular radical conjugate addition with a subsequent enolate hydroxylation. Key features of this synthesis also include a reagent-controlled diastereoselective ketone allylation, an anionic oxy-Cope rearrangement to form a congested quaternary sterocenter, a pyridine-mediated selective ozonolysis, and a Lewis acid promoted Michael-type cyclization.

The root of the Tibetan plant Rhodiola crenulata is part of eastern traditional medicine. Studies have suggested that members of the Rhodiola genus display anticancer properties. In this study we examine the effect of R. crenulata in a cellular model of invasive breast cancer, this disease being the second cause of cancer death among women in the US. Deregulation of the Wnt/β-catenin pathway has been frequently observed in breast cancers and appears to have a key role in the transformation of benign cells to a malignant form. Although mutations of the Wnt growth factor are rarely observed in cancer, the Wnt signaling pathway is often up-regulated by either mutations that result in stabilization of β-catenin or by hypermethylation and subsequent loss of expression of Wnt signaling antagonists like secreted Frizzled-Related Protein 1 (SFRP1) (Hanahan and Weinberg 2000; Miyoshi, Rosner et al. 2002; Reya and Clevers 2005; Suzuki, Toyota et al. 2008) (Hanahan and Weinberg 2000; Miyoshi, Rosner et al. 2002; Reya and Clevers 2005; Suzuki, Toyota et al. 2008) (Hanahan and Weinberg 2000; Miyoshi, Rosner et al. 2002; Reya and Clevers 2005; Suzuki, Toyota et al. 2008). We used an engineered cell line in which SFRP1 expression has been knocked down. These cells were derived from 76NTert cell line, an immortalized human mammary epithelium cell line. The resulting 76NTert-siSFRP1 cells display a mesenchymal-like phenotype, invasive behavior and are more resistant to apoptosis triggered by anchorage independent conditions, or anoikis. Additionally we used a highly invasive estrogen receptor negative (ER-), progesterone receptor negative (PR-), Her2/neu negative (triple negative) breast cancer cells line MDA-MB-231. Treatment of MDA-MB-231 and 76NTert-siSFRP1 cells with an extract of R. crenulata inhibited migration and invasion of both cell types, as compared to untreated cells. Furthermore, R. crenulata sensitizes cells to anoikis but does not increase γ-irradiation induced cell death. We provide evidence that death induced by R. crenulata does not occur through the inhibition of an epithelial-to-mesenchymal transition (EMT). Taken together, our initial results suggest R. crenulata as a potential therapeutic agent for breast cancer patients with mutations in the Wnt/β-Catenin signaling pathway. Additionally, we present evidence that R. crenulata exerts its anti-metastasis effect by inhibiting cell migration and increasing cell attachment to a substrate. We demonstrate that this effect occurs by R. crenulata’s modulation of the Rho GTPase effector ROCK1. We further show evidence that R. crenulata’s effect on ROCK is not limited to cancer cells (in vitro), but also affects isolated and intact embryonic tissues. We discovered that treatment of X. laevis embryos with R. crenulata can cause a spina bifida phenotype, suggesting (1) that compounds in R. crenulata may prove detrimental to a developing embryo, and (2) the active compounds in R. crenulata may prove useful in the study of developmental anomalies that lead to conditions such as spina bifida. More importantly, our results suggest that pregnant women should avoid taking R. crenulata-containing supplements during pregnancy. Compounds in R. crenulata may be contraindicative to the pregnancy and cause injury to a developing fetus. The information provided may help health providers offer better advice on natural supplements to expecting mothers. We also characterized and identified multiple R. crenulata compounds and report predicted protein targets for these compounds. Finally, we provide evidence that R. crenulata affects cancer cell metabolism and suggest potential protein targets of the chemical components of this extract. This study provides new information that will help dissect the mechanisms of action of the R. crenulata compounds and possible synergies amongst them.

Withanolides are a class of ergostane natural products found in plants of family Solanaceae. Plants of this family are used in traditional medicine in Asia and South America. Recently, a series of 17β-hydroxy withanolides were identified from high-throughput screens as inhibitors of androgen-induced changes in gene expression of prostate cancer cells. Therefore, these compounds may have important applications as new therapies against prostate cancer. We have devised a synthetic route to members of this family and their analogues which allows stereoselective introduction of C14, C17 and C20 hydroxyl groups in separate steps. This will allow preparation of differentially hydroxylated analogues so as to identify which contributes to the potency and thus gain a better understanding of the SAR of this class of bioactive molecules. As part of this we have shown that the stereochemical outcome of the epoxidation of Δ 14-15 cholestanes with m-CPBA is controlled by the steric bulk of a C17 substituent. When the C17 is in the β configuration, the epoxide is formed on the α face, whereas if the C17 is trigonal (flat) or the substituent is in the α configuration, the epoxide is formed on the β face. The presence of a hydroxyl substituent at C20 does not influence the stereochemical outcome of the epoxidation. We have successfully introduced aldehyde functionality to the lateral side chain 14 hydroxyl compound. This aldehyde compound is a key intermediate from which many of the withanolides can be made. We have also investigated the introduction of a hydroxyl at the C18 as an entry into the physachenolides. Finally, we have carried out an assessment of the potency of the synthesised compounds against hormone-insensitive prostate cancer cell line, PC-3.

First isolated in 1948 from the Trichothecium roseum fungus, trichothecenes are a diverse class of sesquiterpene natural products with the structures of over 250 congeners established to date. Their general structure consists of the tricyclic “trichothecene” core, marked by the C12,13 exocyclic epoxide and C9,10 olefin, with further structural complexity generated through esterification of macrolide chains to afford macrocyclic trichothecenes including verrucarin A. Owing to their complex structures and potent anticancer activity, trichothecenes have captured the attention of numerous academic groups since the 1970s, resulting in total syntheses of both non-macrocyclic and macrocyclic trichothecenes. The macrocyclic compounds exhibit increased potency, with recent biological studies suggesting involvement of novel molecular targets. The dissertation research described herein is focused on efforts toward the total synthesis of (–)-verrucarol, the flagship trichothecene natural product, and related trichothecene congeners. (–)-Verrucarol was the subject of six total syntheses throughout the 1980s, serving as an entry point for macrocyclic trichothecenes including verrucarin A. Compelled by the recent literature on insight into their therapeutic activity, we have established a concise route to the trichothecene core of verrucarol in eight steps. The construction of the tricyclic system is enabled by a novel samarium (II) iodide (SmI2)-mediated radical cyclization to an enol sulfonate to generate a complex oxabicyclo[3.2.1]octanone ring system. Significant synthetic efforts focused on a key late-stage olefin isomerization, which was ultimately accomplished through Mukaiyama-hydration and elimination. Furthermore, while significant synthetic efforts have gone into constructing the tricyclic trichothecene core, only a single successful, albeit lengthy, enantioselective synthesis of (–)-verrucarol has been reported. To evaluate the full therapeutic potential of trichothecenes, a concise asymmetric synthesis to access the prerequisite tricyclic core is needed. Herein, we report a Cr (III)-salen complex-mediated Diels-Alder cycloaddition of 4-pyrones and the simple diene, isoprene, for rapid access of an enantioenriched precursor for the trichothecene core. Future efforts and synthetic strategies to generate macrocyclic analogues for structure-activity-relationship studies are provided, as focused synthetic efforts to evaluate their clinical potential are sorely needed. / 2025-09-20T00:00:00Z

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