34 KJEMI 4 2025 Universitet og dato: UiT, Kjemisk institutt, 28. mars, 2025 Navn: Mateusz Piotr Sowiński Veiledere: Hovedveileder: Førsteamanuensis Marius Haugland- Grange, Institutt for kjemi, UiT, Co-veileder: Professor Abhik Ghosh, Institutt for kjemi, UiT Opponenter: First opponent: Professor Snorri Þór Sigurðsson, School of Engineering and Natural Sciences, University of Iceland Second opponent: Associate Professor Jens Nolsøe, Fakultet for biovitenskap og akvakultur, Nord universitet Committee coordinator: Professor Jørn H. Hansen, IK, NT-fak Tittel på prøveforelesning: Radicals and Dynamic Nuclear Polarization Tittel på avhandling: Stable spirocyclic nitroxide spin labels Sammendrag: Nitroxides are a class of organic radicals that exhibit remarkable stability under ambient conditions due to kinetic, thermodynamic, and electronic factors. Their unpaired electron and stability render nitroxides valuable as probes and polarisation transfer agents in spectroscopy and imaging techniques. In particular, electron paramagnetic resonance (EPR) spectroscopy extensively utilizes nitroxides as spin labels for structural biology applications. These applications require high stability in reducing biological environments and favourable relaxation properties. Both reduction stability and relaxation parameters are heavily influenced by the nitroxide structure, specifically the nature of the substituents at the quaternary α-positions and the nitroxide ring itself. Whilst spirocyclic groups on the nitroxide scaffold provide the latter, such systems are not inherently resistant to reducing conditions. The research presented in this thesis aimed to enhance the stability of spirocyclic nitroxides through various structural modifications and apply these stable probes to investigate protein structures using EPR methods. We conducted comprehensive synthetic, conformational, and kinetic analyses of a diverse panel of spirocyclic nitroxide scaffolds, accompanied by an investigation of their relaxation parameters. We developed three practically applicable spin labels and successfully applied them in protein spin labelling. Recent experiments have demonstrated that these novel spirocyclic spin labels are promising candidates for future use in in-cell EPR measurements. Universitet og dato: UiT, Kjemisk institutt, 15. november, 2024 Navn: Floriane Baussiere Veiledere: Hovedveileder: Marius M. Haugland Opponenter: First opponent: Professor Oliver Reiser, University of Regensburg, Germany Second opponent: Associate Professor Odd Reidar Gautun, NTNU Committee coordinator: Professor Anette Bayer, IK, UiT Tittel på prøveforelesning: Stereoselectivity in radical reactions Tittel på avhandling: Visible light- mediated alkyl radical additions to alkenyl and alkynyl silanes Sammendrag: Radicals are reactive species that possess a unique reactivity, which enables them to form unusual bonds unreachable by ionic chemistry. In the last twenty years, radical chemistry has benefited from a renewed interest due to the emergence of methods that can initiate radical reactions under mild conditions. Among those, visible light-mediated radical chemistry has become established as a powerful synthetic strategy and is to this day a fast-growing field. Organosilanes are a highly useful and versatile class of compounds that have found multiple applications in synthetic chemistry. Despite belonging to the same periodic table group, significant differences exist between carbon and silicon, which impact their reactivities. While radical additions to unsaturated C-C bonds are well known, similar additions to alkenyl and alkynyl silanes remain underexplored. The work presented in this thesis aimed to investigate and develop new methods for the visible light-mediated intra- and intermolecular addition of alkyl radicals onto vinyl and alkynyl silanes. First, we have developed a general protocol for the introduction of vinyl and alkynyl groups onto sp3 carbons from activated and unactivated alkyl iodide radical precursors, using vinyl and alkynyl silyl tethers as radical
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