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京都大学 / 新制・課程博士 / 博士(農学) / 甲第23954号 / 農博第2503号 / 新制||農||1091(附属図書館) / 学位論文||R4||N5389(農学部図書室) / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 三芳 秀人, 教授 宮川 恒, 教授 森 直樹 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

This thesis presents the development of bis-amino acid-based spiroligomer applications in the areas of molecular recognition and organocatalysis. By taking advantage of the high degree of functionality and chirality of the unique bis-amino acid building blocks, spiroligomer backbones can be synthesized with predefined shapes, functioning as molecular hosts or as enzyme active-site-like pockets. Firstly, we demonstrated that spiroligomers can be designed to act as anion receptors. We designed a collection of spiroligomers that each display two urea groups. The spiroligomer that displayed the two urea groups in a way that they pointed at each other acts as an anion receptor and binds hydrogen pyrophosphate H2PPi anion (H2P2O72−), as demonstrated by an NMR titration experiment. Other spiroligomers that displayed the two ureas demonstrated a variety of behaviors including self-association and gel formation. In later work we explored the use of spiroligomers to develop catalysts. We attempted to design bipyridine/TEMPO-based bifunctional catalysts but they failed to achieve a faster alcohol oxidation rate than the background reaction. We then demonstrated the successful incorporation of metal-salen functional groups into spiroligomers in Chapter 4. Several bis-amino acid-based metal-salen complexes were synthesized and examined as asymmetric catalysts. Although only moderate enantio-selectivity was detected from synthesized Mn-salen catalyzed epoxidation reactions, it provides the first direct evidence that chiral bis-amino acid backbone can act as a chiral pocket that influence substrate selection and the stereochemical outcome of reactions. / Chemistry

The overarching theme of this work is to use weak interactions to improve transition metal catalysis by studying the ways transition metal cations interact with both traditional and novel weakly-coordinating anions. Understanding of these interactions will better allow synthetic chemists to choose appropriate counterions for catalytic transformations, as well as giving mechanistic insight for organometallic reactivity. Additionally, new anions can be synthesized with specific functionalities to improve reactions of interest. A series of ion pairs featuring the [Pd(IPr)(C(O)C6H¬9N)]+ cation were synthesized with various weakly-coordinating anions. Solid- and solution-state interactions with the anions were investigated using X-ray crystallography, NMR and IR spectroscopy, and computation. Proton NMR and percent buried volume calculations inform on the steric properties of the anions, whereas IR and DFT report on the electronics of anion binding. A qualitative scale of anion coordinating ability was created. In the process of this study, a new anion [IMP-H] – was also synthesized based on a phenylimidazole core. A variety of these functionalized [IMP-R] – anions were synthesized, with functionalities such as electron withdrawing groups, tertiary amides, and benzylic alcohols and amines. The coordinating abilities of these anions were analyzed with the techniques described above, with fairly large differences observed between the various functionalities. Further functionalization of these anions may be beneficial from a catalytic standpoint, as coordinating ability of anions has been shown to have dramatic effects on catalytic activity. By designing particular functionalities on anions, efficiency of catalytic processes may be markedly improved. To investigate the effects of the functionalized anions on catalysis, the anions were paired with gold cations such as [(IPr)Au(NCMe)]+, [(JohnPhos)Au(NCMe)]+, and [(tBuXPhos)Au(NCMe)]+. These ion pairs were used as catalysts for several reactions known to show differences in reactivity based on the anion present. While the IPr- and JohnPhos-containing ion pairs both resulted in the formation of gold nanoparticles under various reaction conditions, the tBuXPhos complexes did not, and were therefore more amenable to study. Mild anion effects were seen in the gold-catalyzed hydroalkoxylation of 3-hexyne as well as gold-catalyzed intermolecular [2+2] cycloaddition of α-methylstyrene and phenylacetylene; solvent polarity was also found to have a major effect on the reaction. Other reactions investigated include alkyne hydration, isomerization of 5-hexyn-1-ol to form cyclic vinyl ethers, and propargylation of substituted benzaldehydes. / Chemistry

Due to the very long half-life of Se-79 and its presence in used nuclear fuel, Se is an element of interest in the safety assessment for a deep geological repository (DGR) for used nuclear fuel. Sorption of radionuclides onto the surrounding host rocks and engineered barrier materials is a potential retardation mechanism for radionuclide transport. This thesis investigates the sorption of Se(-II) onto illite, bentonite (engineered barrier material), and shale under high ionic strength conditions relevant to a Canadian DGR. The ionic strength and pH dependence of Se(-II) sorption onto illite, bentonite, and shale were studied. A non-electrostatic surface complexation model was also developed for Se(-II) sorption onto illite and montmorillonite to investigate the sorption mechanisms by which Se(-II) sorbs onto these solids. / Thesis / Master of Applied Science (MASc)

t-Butoxyl radical has been used as a chemical model for hydrogen abstractions in many enzymatic and biological systems. However, the question has arisen as to how well this reactive intermediate mimics these systems. In addressing this concern, absolute rate constants and Arrhenius parameters for hydrogen abstraction by t-butoxyl radical were measured for a broad class of substrates including amines, hydrocarbons, and alcohols using laser flash photolysis. Initially, no obvious reactivity relationship between rate constant and substrate structure was observed for these homolytic reactions. However, by closely examining the Arrhenius parameters for hydrogen abstraction, a pattern was revealed. For substrates with C-H bond dissociation energy (BDE) > 92 kcal/mole, activation energy increases with increasing BDE (as expected). However, for substrates with a lower BDE, the activation energy levels out at approximately 2 kcal/mole, essentially independent of structure. Viscosity studies with various solvents were conducted, ruling out the possibility of diffusion-controlled reactions. Entropy rather than enthalpy appears to be the dominating factor at 25°C, contributing to the free energy barrier for these reactions. Laser flash photolysis was also used to study radical anions. Using an indirect photoexcitation method, the properties of radical anions, generated from aryl ketones, were investigated. These radical anions, such as t-butyl phenyl ketone and cyclopropyl phenyl ketone, measured to have decay rate constants of 1.0 x 106 s-1, although they are known to be persistent when studied electrochemically. They also had measured activation energies around 6.0 kcal/mole and log A values close to 9.5. By extending the molecules's conjugation, the decay rate constants increased to greater than 107 s-1, decreased their activation energy by half, and lowered the log A values to 8.0. This trend was observed in aryl ketones such as trans-1-benzoyl-3-phenyl cyclopropane. It is believed that the generation of a benzyl radical during the decay that facilitates the enhancement of the unimolecular decays. These unimolecular decays were also observed with the previously studied hypersensitive SET probes, 5,7-di-tert-butylspiro[2.5]octa-4,7-dien-6-one and 1,1,-dimethyl-5,7-di-tert-butylspiro[2.5]octa-4,7-dien-6-one. The decay rate constants for these radical anions were measured to be greater than 108 s-1, driven by the formation of an aromatic ring. / Ph. D.