Chapter 1. Ring-Opening Knoevenagel Strategy for the Synthesis of Alpha-Carboalkoxy Cyclopentenones and Their Use in the Diels-Alder Cycloaddition. The Diels-Alder reaction has enabled the synthesis of hundreds of natural products efficiently and with high levels of stereocontrol. Despite over eight decades of development, this reaction is incapable of forming hydrindane ring junctions from alphahydro beta-alkyl cyclopentenones. As such, we used alpha-carboalkoxy cyclopentenones as synergistic dienophiles, but exposed a lack of synthetic tools for assembling strained bicyclic cyclopentenones. We addressed this paucity by developing a ring-opening Knoevenagel reaction for synthesizing these synergistic dienophiles with varying degrees of substitution. The 6 step protecting group free total synthesis of a structurally similar natural product merrekentrone D was achieved to demonstrate the utility of the new method. In addition, the Diels-Alder cycloaddition with these molecules with the Danishefsky-Kitahara diene were studied. The variability of the ring-opening Knoevenagel reaction also led to the development of a decarboxylative Diels-Alder cycloaddition which is degenerate with the alpha-hydro beta-alkyl cyclopentenone Diels- Alder reaction. The hydrindane structures are referred to as iso-Hajos-Parrish ketones which we subsequently demonstrate as powerful building blocks for natural product total synthesis. Chapter 2. Synthetic Studies Towards the Shizukaol Family of Oligomeric Sesquiterpene Natural Products The shizukaol family of oligomeric natural products are one of three oligomeric sesquiterpene families. Three different generations of synthetic strategies towards the unstable and dimeric precursor lindenatriene were studied. The use of the iso-Hajos-Parrish ketone enabled a 10 step, protecting group free, total synthesis of the intermediate. In addition the formation of unnatural dimers was achieved as well as several unexpected results which led to the generalization of our strategy to other natural product families. Chapter 3. Iso-Hajos-Parrish Ketones: Common Intermediates for Sesquiterpene Total Syntheses The three step synthesis of the cyclopropane substituted iso-Hajos-Parrish ketone enabled rapid access to other sesquiterpene families. Through reductase phases the total synthesis of sarcandralactone was achieved in 10 steps without the use of any protecting groups. Studies were also conducted towards achieving the trans-hydrindane ring as a synthetic equivalent to a trans-Diels-Alder paradigm, which was not realized. Additionally, cyclopropane opening of the iso-Hajos-Parrish ketone led to highly oxidized eudesmane skeletons. Our attempts to hydrogenate these molecules in the reductase phase inspired a 6 step total synthesis of des-methyl pinguisone with a strikingly different sesquiterpene framework. Finally, an analysis of redox conservation in total synthesis and the generality of this chemistry to the total synthesis of sesquiterpene natural products will be presented.

PART I Controllable Synthesis of Complex Members of the Resveratrol Oligomer Family Chapter 1. Synthesis and Biological Evaluation of Resveratrol Family Oligomeric Natural Products This introductory chapter traces the history of resveratrol, highlighting the substantial interest in elucidating its potential pharmacological benefits and the ensuing impact on the synthetic community. A plethora of research groups have sought to investigate strategies towards accessing higher order oligomers within the resveratrol family, and these approaches provide context for our own endeavors. Chapter 2. Uniquely Functionalized Resveratrol Dimers: Total Syntheses of Hopeanol and Hopeahainol A In this chapter, we expand upon the utility of a divergent strategy, which has enabled the synthesis of multiple oligomeric, resveratrol-based natural products from a common intermediate. We demonstrate applicability to two exceptional dimeric natural products of the resveratrol family, further developing the truly robust nature of this particular synthetic approach. Chapter 3. Harnessing Redox Reactivity: The Total Synthesis of (±)-Vaticanol A In the final installment of this section, we incorporate distinct methodology into the established chemical toolkit for accessing resveratrol oligomers. Targeting a formidable trimeric resveratrol-based natural product, this work takes advantage of several key insights generated from previous endeavors, particularly selective functionalization techniques. PART II Unexploited Paradigms for Chemical Probe Design, Focusing on Cancer Biology Chapter 1. Introduction to the Drug Discovery Landscape The introduction to Part II presents current approaches to the development of small molecule therapeutics and chemical probes, while concurrently obviating their limitations and the necessity to embrace underappreciated paradigms. Such endeavors could be capable of providing access to many elusive molecular targets. Chapter 2. Small Molecule Inhibitors of GPX4: Attempts at Targeted Covalent Inhibition This chapter discusses a recently validated protein target and our efforts to establish a platform for the development of highly selective, irreversible inhibitors. A unique mechanism of enzymatic activity informs a novel approach towards evaluating the capacity to target specific amino acid residues. Chapter 3. In Silico Design of Protein-Protein Interaction Inhibitors Targeted at the RAS Family of GTPases The final chapter embraces in silico inhibitor design as a strategy towards effectively modulating one of the most challenging protein targets of contemporary drug discovery efforts. As a caveat to traditional in silico approaches, this work sought to validate a multivalent ligand approach towards abrogating key protein-protein interactions.

Furanoeliangolidos são produtos naturais biologicamente ativos que contêm um esqueleto 11-oxabiciclo[6.2.1]undecano. Neste trabalho nós estudamos duas propostas sintéticas para síntese de um modelo simplificado do furanoeliangolido goiazensolido, através de uma reação de Diels-Alder seguida de clivagem da ligação central dos anéis. No desenvolvimento da primeira proposta nós preparamos o composto mesilato, porém as tentativas de efetuar a reação de eliminação resultaram em mistura complexa ou em produtos indesejados. Na proposta seguinte preparamos o éster, e testamos dois caminhos alternativos, entre várias possibilidades, para dar continuidade à síntese. No primeiro caminho o éster foi hidrolisado ao ácido, mas não foi possível obter a amida de Weinreb correspondente. No segundo caminho, o éster foi reduzido ao álcool, que foi oxidado ao aldeído; quando tratado com o ânion da hidrazona, o aldeído forneceu a hidrazona correspondente ao invés do esperado produto de adição de carbânion. Outras alternativas deverão ser investigadas no futuro. / Furanoheliangolides are biologically active natural products containing a 11-oxabicyclo[6.2.1]undecane skeleton. In this work we have investigated two different approaches to synthesize a model of the core structure of goyazensolide. Both approaches involve a Diels-Alder reaction and a bond breaking reaction to produce the polycyclic structure. In the first proposal we prepared mesylate compound. Attempts to effect an elimination reaction, however, resulted either in complex mixture or in undesired products. In the second proposal we prepared ester and investigated two alternative paths, out of several possibilities, to proceed the synthesis. In the first, ester was hydrolyzed to acid, but it was not possible to obtain the corresponding Weinreb amide. In the second path the ester was reduced to alcohol, that was oxidized to aldehyde; this, when treated with the anion from hydrazone, furnished hydrazone instead of the expected product of carbanion addition. Further studies should be developed in the future.

A realização deste trabalho objetivou a avaliação quantitativa da absorção da radiação UVB (290-320 nm) em oito amostras de própolis, incorporadas em base cosmética apropriada, sob a forma de extrato mole, originárias de diversas regiões com diferentes origens botânicas sendo duas de Minas Gerais, três de São Paulo, uma de Santa Catarina, uma do Rio Grande do Sul e outra da Pensilvânia - EUA. A estimativa de absorção foi feita através de método espectrofotométrico com medidas de absorbâncias na faixa entre 290 a 320 nm, tomadas de 5 em 5 nm. Cada medida de absorbância foi relacionada à intensidade e ao efeito eritemogênico da radiação em seu respectivo comprimento de onda. Os resultados tiveram como parâmetro o padrão de referência salicilato de homomentila, aprovado pela FDA para determinação de FPS in vivo. Foi obtido um perfil cromatográfico através de cromatografia em camada delgada para avaliação qualitativa de nossas amostras em relação a alguns flavonóides e ácidos aromáticos, o que nos permitiu constatar a presença de ácido cafeico em todas as amostras analisadas. Foram dosados flavonóides totais por método colorimétrico com cloreto de alumínio, expressos em crisina a 330 nm. Foi feita a comparação entre os resultados de FPS e flavonóides totais e observamos proporcionalidade direta entre a maioria das amostras, o que confirma a ação de absorção de radiação ultra-violeta por flavonóides colhidos pelas abelhas em plantas. / The aim of this work was to evaluate quantitatively the UVB absorption (290-320 nm) of propolis, contained in eight cosmetic samples as soft extract, from different botanical origins and several regions, such as Minas Gerais, São Paulo, Santa Catarina, Rio Grande do Sul and Pennsylvania (USA). A spectrophotometric method using absorbance measurements in a range of 290-320 nm, taken at 5 nm intervals, was used to asses the absorbance. Each absorbance measurement was related to both intensity and erythemal effect of the radiation at its respective wavelength. Homosalate, which is approved by the FDA as reference standard, was used for the determination of SPF in vivo. Chromatograms of the samples were obtained by thin-layer chromatography to evaluate the presence of some flavonoids and aromatic acids in the samples. This technique allowed the detection of caffeic acid in all the analyzed samples. The total flavonoids content was assayed by the colorimetric method using aluminum chloride, and the results were expressed in chrysin at 330 nm. A comparison between the SPF results and the total flavonoids contend was done and a direct relationship between most of the samples was observed, confirming the absorbing ultraviolet radiation property of the flavonoids collected by bees.

This thesis deals with the proposal that environmentally benign items of free standing furniture may be produced by the use of such well established techniques as training and grafting natural tree growth to shape. The project has been driven by the growing environmental concerns of which mankind has become aware in the late twentieth century, and which are starting to exert such a powerful influence in the twenty first. A broad history of man's use and control of natural tree growth, ranging geographically from Europe to Australia, and in size from hand held agricultural picks to eighteenth century sailing ships, is followed by a brief description of the ways in which the explosive increase in world popuanon. together with the expanding industrial activities of the Western consumer society, are feared to be threatening the stability of the natural environment. The various disasters and catastrophic accidents which have brought this situation to the attention of the general public are briefly surveyed, together with National, International and a range of Industrial responses. As one of the professions most closely concerned with the production of consumer items, the various reactions of the Design Community are similarly examined. In conclusion, the author's proposal for an experimental item of furnitureenvironmentally benign in production, use and disposal - is described and illustrated. A simple free standing three legged stool, the form of both the item itself and that of the jig required to control it's growth, are described and illustrated. The growth of examples of this, carried out on three sites across southern Britain are documented, experimental results reported and discussed. A further range of designs suitable to be produced using this method of controlling and grafting natural growth is proposed, and suggestions made for further experimentation.

Actinomycins are a class of compounds consisting of phenoxazinone-like core attached to two peptidolactone rings, denoted as α and β. A unique component of a few families—actinomycins G, Y, and Z—is a chlorinated β-ring threonine residue. Families G and Y also contained an actinomycin that possess a β-ring heterocycle (actinomycins G5 and Y5, respectively); prior to this work, no β-ring heterocycle-containing actinomycins were reported for the Z family. Unlike other actinomycin derivatives, Y5’s cytotoxicity was abolished while still maintaining some antibacterial potency. We constructed a model compound to probe the physical properties of the actinomycin core to test conditions under which heterocycle formation would occur. We also analyzed the gene clusters of these actinomycin producers for gene candidates to from this structural motif. We found the the actinomycin core aniline to have pKa values of 2.976 and 8.429 and a significant shift in UV absorption between 300-310nm when the group becomes charged. We also found cyclization conditions and no obvious gene candidates to form the β-ring heterocycle based on our gene cluster analysis. We hypothesize that the familial diversity of the actinomycin G, Y and Z familes is due to the reactivity of the phenoxazinone-like core.

Polyketides are a large group of structurally diverse natural products that have shown a variety of biological activities. These molecules are synthesized by polyketide synthases (PKSs). PKSs are classified into three types based on their sequence, primary structure, and catalytic mechanism. Because of the bioactivities of polyketide natural products, this study is focused on the engineering of PKS pathways for efficient production of useful bioactive molecules or structural modification to create new molecules for drug development. One goal of this research is to create an efficient method to produce pharmaceutically important molecules. Seven biosynthetic genes from plants and bacteria were used to establish a variety of complete biosynthetic pathways in Escherichia coli to make valuable plant natural products, including four phenylpropanoid acids, three bioactive natural stilbenoids, and three natural curcuminoids. A curcumin analog dicafferolmethane was synthesized by removing a methyltransferase from the curcumin biosynthetic pathway. Furthermore, introduction of a fungal flavin-dependent halogenase into the resveratrol biosynthetic pathway yielded a novel chlorinated molecule 2-chloro-resveratrol. This demonstrated that biosynthetic enzymes from different sources can be recombined like legos to make various plant natural products, which is more efficient (2-3 days) than traditional extraction from plants (months to years). Phenylalanine ammonia-lyase (PAL) is a key enzyme involved in the first biosynthetic step of some plant phenylpropanoids. Based on the biosynthetic pathway of curcuminoids, a novel and efficient visible reporter assay was established for screening of phenylalanine ammonia-lyase (PAL) efficiency in Escherichia coli. The other goal of this research is to characterize and engineer natural product biosynthetic pathways for new bioactive molecules. The biosynthetic gene cluster of the antibacterial compound dutomycin was discovered from Streptomyces minoensis NRRL B-5482 through genome sequencing. Confirmation of the involvement of this gene cluster in dutomycin biosynthesis and creation of a series of new molecules were successfully conducted by rationally modifying the biosynthetic pathway. More importantly, a new demethylated analog of dutomycin was found to have much higher antibacterial activity against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.

In the fight against disease and illness, nature has provided mankind some of our best therapeutics in the form of secondary metabolites. The plant, fungi and animal phyla inhabiting the Earth produce diverse and unique chemistry that can be used in our fight against disease. In the growing threat of drug resistance and pathogen evolution, the field of natural products chemistry strives to explore new biological and chemical diversity sources, and develop innovative methodology to identify and isolate new chemistry faster than ever. The dissertation herein presented is one such effort to find new, bioactive chemistry from the marine environments. New biodiversity sources, from the tropical Floridian mangrove forests to the cold waters of the Antarctic oceans, were evaluated for the new, unique chemistry they produce. A large-scale screening of epigenetically modulated mangrove fungi was undertaken, producing a large, biologically and chemically diverse extract library. New methodology was developed in order to evaluate these extracts, leading to rapid identification and isolation of known and new bioactive metabolites. From the Southern Oceans, a collection of sponges was studied, and a new, highly unique peptide was isolated and characterized. These efforts were undertaken in the continued effort to isolate new, unique lead compounds.

This thesis described the chemical investigations of natural products from Australian marine sponge-derived fungi. Sponge samples were collected from the Great Barrier Reef, Queensland, Australia, by Queensland Museum. The thesis is divided into eight chapters and can be devided into two major parts. The first three chapters comprised the first part of the thesis: Chapter 1 outlined the research background, literature review of marine fungal secondary metabolites; Chapter 2 introduced fungal culture and storage background knowledge, and the list of isolated marine fungal strains. Chapter 3 introduced the background of the thrombin inhibition assay and assay results. The second part (Chapter 4 to 7) of this thesis is focused on chemical isolation and structure elucidation of secondary metabolites from isolated fungal strains, mostly active strains against thrombin. An unidentified fungal strain, FS-G315858 (T)-Y, isolated from the frozen sponge sample Dysidea sp.1400 produced five peptide compounds (chapter 4, 16-20). Compound 16 is a polypeptide which features the same relative configuration with a known compound unguisine A, and compounds 17-20 are diketopiperazines. Active fungal strains FS-G315695 (T)-Y and FDPS-61732-YB were isolated from different sponge samples. However, they were identified to be the identical fungal strain Eurotium rubrum; the chemical isolation of FS-G315695 (T)-Y from its mycelia EtOAc extract resulted in three compounds (chapter 5, 17-19). Compounds 18 and 19 were identified to be flavoglaucin and iso-dihydroauroglaucin. Compound 17 was identified to have the same relative configuration with a known compound neo-echinulin A. The chemical isolation of FDPS-61732-YB from its broth EtOAc extract resulted in several diketopiperazines (chapter 5, 27-29). Another active fungal strain FS-G315695 (T)-WY was identified as Aspergillus ochraceous, the chemical isolation of its mycelia EtOAc extract resulted in one benzodiazepine compound (chapter 6, 18), together with two fatty acids (chapter 6, 16-17). The structure of compound 18 was elucidated and identified to have same relative configuration with the known compound circumdatin E. Media comparison for active fungal strain FS-G315695 (T)-Y was conducted and this work resulted in producing several neo-echinulin analogues (chapter 7, 1-3). The isolation and structure elucidation of these compounds were reported in chapter 7.

Isolation and structure elucidation of natural products from marine sponges and an invertebrate were performed. The marine sponges and invertebrate were obtained from three locations including South East Queensland, in Australia, Pontianak in West Kalimantan, and Tulamben, in Bali, Indonesia. The natural products were purified using chromatographic techniques, the structures were elucidated by means of extensive 1D and 2D NMR spectroscopy and some were confirmed by X-ray crystallography. Five known compounds and potentially a new metabolite were identified from three different sponges and a species of nudibranch obtained in Mooloolaba, South East Queensland in Australia. Furospinosulin-1 (4.5), a linear sesterterpenoid, was identified from a sponge coded 20-1-07-1-7 while imidazole alkaloids, preclathridine A (4.9) and clathridine (4.10), were characterized from sponge 22-4-07-2-1. The ethyl acetate extract of sponge 14-7-07-1-1 yielded a polyacetylene fulvinol-like compound (4.15) and potentially a new metabolite compound 5 (4.21). Additionally, a specimen of Chromodoris kuiteri furnished a cyclic macrolide latrunculin A (4.27). There were six secondary metabolites identified from Aaptos aaptos, two of which to the best of our knowledge were new compounds. Aaptamine (5.1), a chemotaxonomic marker of the sponge A. aaptos, 9-demethylaaptamine (5.3) and a biosynthetically unrelated compound (-)-jaspamide (5.31) were found as major constituents of the dichloromethane extract of the sponge. On the other hand, a known indole-3-carbaldehyde (5.10), and the two new natural products methyl 3-(8,9-dimethoxy-4H-benzo[de][1,6]naphthyridin-4-yl)propanoate (5.11) and 8,9-dimethoxy-4H-benzo[de][1,6]naphthyridine-5,6-dione (5.30) were isolated as minor components. During a two-month fieldwork trip to Tulamben, Bali, six different sponges were obtained. Investigation of a blue colored sponge Petrosia sp. afforded two isoquinolinequinone metabolites, namely mimosamycin (5.35) and O-demethylrenierone (5.36). A new 3-alkylpiperidine metabolite, tetradehydrohaliclonacyclamine A (6.28), was isolated from a sponge Halichondria sp. The structure and relative stereochemistry of 6.28 were determined from analysis of 2D NMR data and interpretation of coupling constants. Suitable crystals that were grown from hexane: ethyl acetate (1:3) allowed the determination of the absolute configuration of 6.28 and it was established to be 2S, 3S, 7S, and 9S on the basis of X-ray crystallographic data. The isolated compound (6.28) appeared to be as a single enantiomer according to chiral HPLC. The parent compounds, haliclonacyclamine A (6.19) and B (6.20), were re-isolated from a sample (coded BK-Hal-12-AIK) obtained from a previous project on Haliclona in our group. Their absolute configurations were determined for the first time by X-ray crystallography and they were established to be 2R, 3R, 7R, and 9R.