Th.--Sci phys.--Grenoble 1, 1980. N°: 56. / Extr. en partie de Journal de physique. Colloque C5, 40, 1979, 5, 364-365 ; 41, 1980, 6, 181-184 ; de Physical review letters, 43, 1979, 4,304-307 ; de Journal of magnetism and magnetic materials, 1980, 989-990 et de Valence instabilities and narrox band phenomena, 1977, 513-515.

D.Phil. / The topic of this thesis centres around the construction of carbocycles from carbohydrates involving the use of SmI2 as reagent. Carbocycles, in particular functionalised cyclopentanes, form important substructures in a plethora of natural compounds, many of which are biologically active. The conversion of carbohydrates into stereodefined cyclopentanoids represents an attractive means of generating this type of compounds. The SmI2-mediated cyclisation of hex-5-enals, derived from suitably substituted carbohydrate precursors via a zinc-mediated Grob-fragmentation reaction, was found to be a facile reaction generating stereodefined cyclopentanols in moderate yields. The effect of varying stereochemistry and substitution pattern on the outcome of the cyclisation was also investigated. In order to achieve a more efficient route to the cyclic products, a Grobfragmentation based on SmI2 was investigated. The substituent at the anomeric position of the carbohydrate was found to be crucial to the success of the fragmentation. This protocol gave rise to conditions under which fragmentation and cyclisation could be effected in a tandem fashion mediated by SmI2. Various attempts at intermolecular trapping of the organosamarium species generated after cyclisation proved fruitless. In order to circumvent these obstacles a tandem radical bicyclisation reaction was investigated for the construction of highly functionalised bicyclic ring systems. This approach proved to be a successful alternative for incorporating functionality at the exocyclic carbon atom which is otherwise difficult to achieve. The second part of this work is directed at the synthesis of stereodefined alkoxyaminocyclopentanes from carbohydrates promoted by SmI2. The intramolecular trapping of a radical by an oxime ether represents an attractive means of generating these compounds. The preparation of the iodo oxime ether starting materials from suitably substituted carbohydrates is discussed. The radical cyclisation under the action of SmI2 was found to be a facile process providing a rapid route to aminocyclopentanes which are used as key intermediates for the preparation of carbocyclic glycosidase inhibitors and analogues. In the third part of this work, the construction of functionalised cyclobutanols from carbohydrate precursors is discussed. The 4-exo-trig cyclisation holds promise as a general route for the stereoselective synthesis of highly functionalised cyclobutanols. Initial attempts at the 4-exo-trig cyclisation proved fruitless. It was subsequently established that the radical acceptor plays a crucial role in the success of the transformation. This led to the isolation of the first carbohydrate derived cyclobutanol. The final part of this thesis involves the development of a new approach for the conversion of suitably functionalised pentose derivatives into chiral cyclopentanols. Cyclisation of a ribose derived hemiacetal via its in situ formed hex-5-ynal is discussed. This approach opens new possibilities for the construction of complex carbocycles from readily available carbohydrate starting materials.

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Thesis (M.S.)--Western Washington University, 2010. / Includes bibliographical references (leaves 38-40). Also issued online.

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This study utilizes recent advances in the analysis of neodymium (Nd) and samarium (Sm) by thermal ionization mass spectrometry (TIMS) to constrain timescales of heating and fluid flow within the lithosphere. Garnet grows during metamorphism and can be linked to its pressure and temperature of growth, while carbonate mineralization ages can be linked to hydrothermal fluid flow. The ability to date these common minerals makes it possible to unravel the timing and duration of tectonometamorphic processes. Garnet from the Eoarchean Nuvvuagittuq Supracrustal Belt (NSB) in Québec, Canada yields an age of 2574.66 ± 0.72 Ma. This is the most precise Neoarchean age reported for this terrane and was achieved through a modified partial dissolution procedure designed to remove the effects of much older (up to 3.8 Ga) inherited mineral growth. An accurate age for the most recent metamorphic garnet in the NSB is critical, as the (controversial) Hadean Nd model age calculations for this terrane depend on the time at which the 147Sm/144Nd systematics were last altered. Carbonate mineralization ages are explored for a diverse group of thirty samples using a novel sequential acid extraction procedure. Through this procedure it is possible to constrain carbonate mineralization in a variety of geologic settings (metamorphic fluid flow, hydrothermal and ore-forming systems) to ± 20 Myr. Zoned and bulk garnet geochronology at ten sites within a unusually localized area (~5 km2) of high temperature granulite-facies metamorphism in Bristol, New Hampshire reveals multiple brief (<1 Myr) periods of garnet growth focused between 393 and 386 Ma, at peak temperatures of 730-850°C. Comparison with garnet growth ages and temperatures , in central Massachusetts (364 Ma at 950°C) and Connecticut (341 Ma at 1000°C) reveal a regional trend of pulsed high temperature garnet growth spanning ~60 Myr from north to south, the same time span bracketed by associated igneous rocks dated via zircon geochronology. Ultrahigh metamorphic temperatures were achieved during the Acadian Orogeny in New England in localized, short pulses, likely related to igneous heating and/or associated fluid flow above and beyond the regional heating due to tectonic overthickening.