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Allium Genus Natural Product Isolation and Reactions of Cyclopropanes from Oxabenzonorbornadienes

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Title: Allium Genus Natural Product Isolation and Reactions of Cyclopropanes from Oxabenzonorbornadienes
Author: McKee, Mary K
Department: Department of Chemistry
Program: Chemistry
Advisor: Tam, William
Abstract: The Allium genus has attracted attention throughout history for its diverse and remarkable functions. In this study, an antimicrobial natural product was isolated from Allium tricoccum. Isolation methods began with maceration of the plant sample, filtration, and liquid-liquid extraction using nonpolar solvents. Crude purification methods included decolourizing carbon, and normal phase flash column and preparatory high pressure liquid chromatography. The natural product was identified by 1H and 13C NMR experiments and confirmed by HRMS analysis as methylallicin (26 mg). Antimicrobial activity was conducted by the Li group, Animal and Poultry Science, University of Guelph. Heterobicyclics have received much attention in the literature for their diverse and efficient applications in synthesis. In this study, a successful continuous flow cyclopropanation protocol was developed using diazomethane gas under palladium catalysis in diethyl ether. Exploration was accomplished through application to a total of 17 good examples of C1- and aryl-substituted oxabenzonorbornadienes, giving good to excellent yields (64-96%) and complete exo stereoselectivity. One mixture of regioisomeric pairs is also yet unseparated by chromatographic techniques employed. Nucleophilic ring-opening of the parent cyclopropane was unsuccessful with Grignard and yielded poorly with organolithiums. However, higher-order cyanocuprates R2CuCNLi2 in tetrahydrofuran yielded highly substituted dihydronaphthalenols with good to excellent yields (13-95%).
URI: http://hdl.handle.net/10214/7700
Date: 2013-12
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