Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 220-232). Also available on the World Wide Web.

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Natural products play a historical role in the discovery of medicine but present unique challenges for chemical isolation, identification and production. In this work we describe the identification of twenty novel diterpenoids. These were isolated by use of chromatography, and the structures determined by spectroscopic methods, primarily 1D and 2D NMR. Six of these possess unprecedented diterpenoid skeletons and two of them show significant growth inhibitory effects on cancer cell lines in vitro (GI50 < 10 μM). The biomimetic semisynthesis of diterpendoids and analogues is also presented. Access to the bielschowskyane carbon skeleton by dearomatization of a furanocembranoid precursor is described. Highlights include a stereoselective alkene epoxidation, a novel kinetic furan dearomatization method, and an efficient [2+2] photochemical cycloaddition. The role of conformational steering was studied spectroscopically using VT 1H-NMR and NOESY as well as quantum chemical calculations at the DFT level of theory. We also disclose a biomimetic synthesis of providencin using a photochemical Norrish-Yang cyclization. This provided the absolute configuration by chemical correlation with the precursor bipinnatin E, the latter determined by x-ray diffraction. An unexpected, regioisomeric byproduct was observed and a possible mechanism is proposed. A biomimetic synthesis of the diterpene alkaloid aceropterine is also described, using an epoxidation-rearrangement cascade. This work led to a revised structure of aceropterine, formulated by spectroscopic methods. Finally, the isolation and structure elucidation of a novel, cyclic lipopeptide from Pseudomonas sp. is described. The compound was obtained using a unique antibiotic crowd sourcing approach and the structure determined by spectroscopic methods and advanced Marfey’s analysis. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

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The projects described in this dissertation are focused on compounds derived from marine organisms collected from the western Atlantic marine environment. Chapter 1 provides an introduction to the study of natural products chemistry, marine natural products, and overview of the research undertaken from natural product chemists. Chapter 2 describes the isolation and structure elucidation of a series of rare diterpenoids from the gorgonian Briareum asbestinum, together with their conformational analysis and biosynthetic interconversions. These rare diterpenes from Briareum asbestinum are linked by an unusual transannular oxa-6π electrocyclization which is described in detail and this work demonstates the biomimetic hemisynthesis of briareolate esters L (19) to B (22) achieved via an intermediary, briareolate ester G (2), through a controlled set of photoinduced isomerizations and a unique photochromic transannular oxa-6π electrocyclization. This work focuses largely on the mechanistic understanding of the photochemical production of these briarane diterpenoids and illustrates a unique UVA/UVC, photochromic switch which induces a transannular oxa- 6π electrocyclization. Chapter 3 describes the assay-guided isolation of marine antioxidants. This chapter focuses on the screening of marine organism extracts using the Ferric Reducing Antioxidant Power (FRAP) assay for antioxidant activity guided isolation of marine natural products. The chapter concludes with the activity guided isolation and structural elucidation of 1-O-palmitoyl-2-O-myristoyl-3-O-(6-sulfo-α-D-quinovopyranosyl)- glycerol (40) to show direct antioxidant potential through FRAP analysis. Chapter 4 describes the isolation, structural elucidation and pharmacological evaluation of the novel secondary metabolites iso-PsA(45), Iso-PsC (46), iso-PsD (47) as well as known Pseudopterosins A(41), B(42), C(43), D(44), K(48), K2’OAc(49), K2’OAc(50). These secondary metabolites were evaluated for both cytotoxicity. The chapter concludes with the screening of these compounds as αβ-amyloid fibril modulators utilizing atomic force microcopy (AFM). / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

In recent years, marine natural products in drug development increasingly wide range of applications. Both Taiwan's geographical location and climate are creating a rich marine biodiversity. Hence there is needed to construct a marine natural product database which with Taiwan features. The goal of this study is to establish a Taiwan's marine natural product database, with preliminary collected Formosan soft coral diterpenoids natural products from Taiwan for drug development features. The database included normal physical and chemical properties of compounds and biological activity assay from literature. Key project for the database is to construct three-dimensional structure information for marine natural products. In this study, it was to build and to check the correct three-dimensional structure by use of computer simulation study comparing with nuclear magnetic resonance (NMR) spectroscopy information from literature. The identification of the folding errors in three-dimensional structure of various compound skeleton types by computer was also discussed. And there was also discussed the relationship between potential energy and three-dimensional structure of compounds by compare with computer simulated structure and NMR structure.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Kubanek, Julia; Committee Member: Fernandez, Facundo M.; Committee Member: Harvey, Stephen C.; Committee Member: Hay, Mark E.; Committee Member: Hud, Nicholas V. Part of the SMARTech Electronic Thesis and Dissertation Collection.