Browsing by Subject "Alkaloids"
Now showing 1 - 13 of 13
Results Per Page
Sort Options
Item Alkaloid biosynthesis in Claviceps purpurea PRL 1980 protoplasts(Texas Tech University, 1979-12) Lu, Jean-PhonNot availableItem Exploring a Symmetry Based Logic for Palau'amine Synthesis(2008-05-13) Li, Qingyi; Harran, PatrickPalau'amine is a natural product originally isolated in 1993 from the marine sponge Stylotella aurantium. It is reported to posess impressive biological activities, including: antifungal, antibacterial, and antineoplastic characters. Moreover, it is a strong immunosuppressant (IC50<18ng/mL, allogenic lymphocyte reaction). The molecule has a complex polycyclic structure having a contiguous array of eight stereogenic centers. It is unusually rich in heteroatoms. A recent revision of its relating stereochemistry has brought further attention to this fascinating molecule. The current strategy of our group features a chlorination initiated cascade process on a symmetric precursor that assembles the skeleton of palau'amine with in a single operation. A symmetric bisalkylidene precursor for this process was synthesized. During the process, two new methodologies were developed: a titanocene dichloride mediated regioselective and stereoselective dimerization of heterocyclic dineolates; and a chemoselective Rh(I) carbene complexes catalyzed conjugation hydrosilylation of enamides. Our core idea was subsequently validated by the formation of the spirocyclopentane motif in palau'amine by an electrophilic halogen induced desymmetrization.Item Hydroxylation of intermediates in clavine alkaloid biosynthesis.(Texas Tech University, 1974-08) Bajwa, Raghbir SinghNot availableItem In vitro metabolism of agroclavine and elymoclavine in Claviceps sp.(Texas Tech University, 1983-08) Kim, Soo-unNot availableItem In vivo and in vitro metabolism of clavine alkaloids(Texas Tech University, 1970-08) Hsu, Joan Chung-Ying Chen,Not availableItem Metabolism of 4-Dimethylallyltryptophan in Claviceps purpurea PRL 1980(Texas Tech University, 1975-05) Saini, Mohan SinghNot availableItem Separation of alkaloid isomers and stereoisomers with beta-cyclodextrin bonded phases(Texas Tech University, 1987-08) Ward, Karen DeniseNot availableItem Studies directed towards the synthesis of secu'amamine A(2009-08) Padilla Acevedo, Angela Isabel; Magnus, Philip D.Herein is described our synthetic studies towards the synthesis of secu'amamine A, a member of the Securinega alkaloids. The first chapter describes the isolation, biological significance and previous synthesis of secu'amamine A. Chapter 2 discusses our proposed biogenetic origin of secu'amamine A from allosecurinine and the model studies to support the intermediacy of the putative aziridinium ion. Chapter 3 discusses our synthetic approach to the formation of rings A and C, as well as investigations on the regioselective functionalization of 1,2-dihydropyridines. Chapter 4 discusses the synthesis of ring D from ring D' and the transformations of our advanced intermediates with different carbamate protective groups. Chapter 5 consists of experimental details and characterization data for all new compounds.Item Studies on the Daphniphyllum alkaloids : strategies towards the synthesis of daphnicyclidin alkaloids(2008-05) Harrington, Ryan Matthew, 1980-; Magnus, Philip D.Herein describes our approaches to the Daphniphyllum alkaloids. Specifically targeted are the recently isolated daphnicyclidins. The first chapter describes the structural diversity and biological properties of this class of alkaloids. Chapter 2 discusses some exploratory chemistry towards the daphnicyclidin fused tricycle. Chapter 3 describes the use of cyclopropanes in synthesis and their use in our ring expansion strategy. Preliminary results on the key cyclopropane ring expansion and the stereoselective quaternary center formation are also discussed. The chemistry concerning the diasteroselective cyclopropanation of a key intermediate and further details concerning the cyclopropane ring expansion are delineated. Chapter 4 contains the experimental details and characterization data for all new reported compounds.Item Synthetic Studies Toward Selected Members of the Pyrrole-imidazole Alkaloids: Axinellamine, Konbu?acidin and Palau' amine(2011-10-21) Zancanella, ManuelThe pyrrole imidazole alkaloids (PIA) is an ever-growing family of structurally related natural products isolated from several species of sponges which now features more than one hundred memebrs. Their complex molecular architectures, and in some cases, significant biological activities, have made these alkaloids the synthetic targets of a number of research groups across the world. In our approach, following early biosynthetic proposal by Kinnel and Scheuer and Al-Mourabit and Potier, it was envisioned that several of these alkaloids, namely palau?amine, axinellamine, konbu?acidin, styloguanidine and massadine, could be derived from a common chlorocyclopentane precursor through different modes of intramolecular cyclization. Building on the work done previously in our research group by Dr. Anja Dilley, Dr. Paul Dransfield, and Dr. Shaohui Wang, my investigations led to the synthesis of the angular aza-triquinane core of axinellamine and the peculiar transazabicyclo[ 3.3.0]octane core of palau?amine. In my further studies mono- and bis-pyrrole advanced intermediates were synthesized that contain the complete carbon framework of the target natural products. However, attempts to induce the pivotal, potentially biomimetic cyclizations expected to deliver the cores of the target alkaloids proved to be rather challenging, resulting in inconsistent and irreproducible results and leading to the exploration of an alternative, ?abiotic? approach. My efforts in this direction resulted in the synthesis of a pentacyclic enamine precursor to styloguanidine and a pentacyclic carbinolamine suitable for the synthesis of palau?amine. Final attempts to complete the target natural products were however unsuccessful.Item The cell-free biosynthesis of clavine alkaloids(Texas Tech University, 1969-08) Cavender, Finis L.Not availableItem The conversion of 4-dimethylallyltryptophan to clavicipitic acid in vitro.(Texas Tech University, 1975-05) Cheng, Mary M LNot availableItem The total synthesis of (±)-renieramycin g and studies toward the synthesis of (±)-lemonomycin and (±)-saframycin b(2005) Matthews, Kenneth Stanley; Magnus, Philip D.