No description available.

Norzoanthamine is a complex heptacyclic marine alkaloid isolated from colonial zoanthids. It potently inhibits loss of bone weight and strength in a postmenopausal osteoporosis mouse model, but its mode-of-action remains unknown. The scarcity of this natural product from its natural source and the need to access analogs for structure-activity relationship (SAR) study make it necessary to chemically synthesize this compound. However, the complex molecular skeleton, especially the highly functionalized and stereochemically complex ABC core structure of the natural product poses a significant challenge. As part of our efforts to develop a practical synthetic route to norzoanthamine, we systematically explored a transannular Michael reaction cascade in the context of the synthesis of angular 6-6-6 tricyclic ring system, a mimic of the ABC core structure of norzoanthamine. Using 1,7-bis-enones in the form of 14-membered macrocyclic lactone as model substrates, we demonstrated that both E,Z- and E,E-macrocycles underwent facile transannular reactions to give cis-syn-cis and trans-anti-trans ring systems, respectively. However, Z,E- and Z,Z- macrocycles did not cyclize under similar reactions. The similarities and differences between transannular Diels-Alder reactions and this transannular cyclization process were also disclosed. Building upon these preliminary studies, we developed a 12-linear step synthesis of the ABC carbocyclic core of norzoanthamine. It features an organocatalytic asymmetric intramolecular aldolization to set the stereochemistry of the entire molecule, a fragment coupling based on selective alkylation of a bis-enolate, and a transannular Michael reaction cascade for rapid and stereoselective synthesis of the polycyclic core. Subsequent Claisen rearrangement enabled installation of a handle for introduction of the bottom piece to complete the total synthesis. Other efforts toward the total synthesis have also been discussed.

Issued also as Thesis--University of Chicago. / "Studies from the Psychological Laboratory of the University of Chicago."

Thesis (doctoral)--Lund University, 1998.

Issued also as Thesis (Ph. D.)--University of Chicago, 1912. / "Studies from the Psychological Laboratory of the University of Chicago."

Thesis (doctoral)--Lund University, 1998.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18097号 / 理博第3975号 / 新制||理||1573(附属図書館) / 30955 / 京都大学大学院理学研究科化学専攻 / (主査)准教授 依光 英樹, 教授 丸岡 啓二, 教授 大須賀 篤弘 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

<p>  </p> <p>Dehydrogenation is a common reaction used to upgrade paraffins to olefins in the chemical and oil industries. Given the increased abundance of inexpensive alkanes due to the worldwide shale gas boom, this reaction has become increasingly important. Conventional industrial techniques such as thermal cracking and steam cracking have relatively poor olefin selectivity and thus require energy-intensive separations. Industry is increasingly relying on catalytic dehydrogenation as a more environmentally friendly alternative to generate olefins. While recent development in catalyst materials has largely solved issues with activity and selectivity, issues with catalyst stability remain. Deactivation mechanisms such as coke formation and phase changes plague the short-term and long-term stability of these catalysts, often requiring frequent and intensive regeneration procedures. </p> <p>This thesis will explore several strategies for mitigating the deactivation of dehydrogenation catalysts. This includes the modification of catalyst properties and reaction conditions, such as the catalyst support and the use of H2, to mitigate coke formation and even regenerate catalyst materials non-oxidatively, thus increasing the catalyst lifetime. Secondly, this thesis will cover the discovery of new catalyst materials through computational predictions based on descriptors assessed from several previous works. Experimental validation of these predictions led to the discovery of several new Rh and Ir based alloy materials that are remarkably selective and stable for propane dehydrogenation (PDH). Lastly, the contribution of electronic structure of PDH catalysts will be assessed using a new characterization technique that will help relate catalyst properties to catalyst performance and stability. </p> <p>Several advanced X-ray synchrotron techniques have assisted the analysis and discovery of catalyst materials in this work. Particularly, this includes difference-EXAFS to assess the surface structure of alloy catalyst materials as well as the newly-developed non-resonant X-ray emission spectroscopy (NR-XES) to assess the electronic structure of the 5d valence band for Pt catalyst materials. To extend this work further, the goal is to apply this new technique to additional catalyst materials, such as Pt alloys or single site Pt supported on CeOx, in order to measure the effect of different adsorbates on the electronic structure of the Pt catalyst. This will help derive fundamental insights to drive the development of the next generation of stable dehydrogenation catalyst materials.  </p>

No description available.

This thesisd escribess yntheticw ork carriedo ut on two separatep rojects. (i) Synthetics tudiest owardst he total synthesiso f galanthamine (ii) The total synthesis of 2-Benzoyl-9-azabicyclo[4.2.1 ]non-2-ene Galanthamine is an amaryllidaceae alkaloid processing a rigid tetracyclic structure with a fused dihydrobenzofuran onto a cyclohexenol and a bridging tertiary amine. 2-Benzoyl-9-azabicyclo[4.2.1]non-2-ene is an analogue of anatoxin-a, whereby the acetyl side chain has been substituted with a benzoyl group. Anatoxin-a itself possesses a 9-azabicyclo[4.2.1]nonane framework. Although structurally very different they both share a common feature in that they interact with acetylcholine receptors. Hence chapter 1 is an introduction to Alzheimer's disease which is primarily caused by a lack of acetylcholine. A literature review of the total syntheses of galanthamine and a background of galanthamine is described in chapter 2, whilst chapter 3 details the forward synthesis to the galanthamine framework but with a cyclopentenyl instead of a cyclohexenyl moiety and subsequent attempts for the elaboration of the cyclopentenyl into its corresponding cyclohexenyl moiety. Chapter 4 and 5 describes the published total syntheses of anatoxin-a and analogues of anatoxin-a, whilst chapter 6 concludes the total synthesis of the phenyl analogue of anatoxin-a via a key selenium mediated transannular cyclisation of a Boc-(3-Lactam to furnish the 9-azabicyclo[4.2. l]nonane ring system.