silicon and nitroxyl

This article explores a new, convenient route to beta-phosphorus nitroxides. Specifically, the reaction sequence involves the novel 1,3-addition of trimethylsilyl phosphites (e.g. diethyl) or trimethylsilyl phosphines (e.g. diphenyl) to aldo-nitrones [e.g. alpha-phenyl-N-tert-butylnitrone (PBN) or 5,5-dimethyl-l-pyrroline-N-oxide (DMPO)] or keto-nitrones [e.g. 2-ethyl-5,5-dimethyl-1 pyrroline-N-oxide (2-Et-DMPO) or 2-phenyl-5,5-dimethyl-l-pyrroline-N-oxide (2-Ph-DMPO)] to form alpha-phosphityl- or alpha-phosphinyl-O-silylhydroxylamines. Acidic hydrolysis provides the corresponding hydroxylamines that are easily oxidized to the title beta-phosphorus-nitroxides. ESR spectroscopic analysis revealed some very large beta-phosphorus hyperfine splittings (i.e. in excess of 5 mT). For this reason and their remarkable stability (persistence) some of these nitroxides show promise as integral components in new, improved weak-field dynamic nuclear polarization (DNP) magnetometers.

Topics: Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Hydroxylamines; Magnetic Resonance Spectroscopy; Molecular Structure; Nitrogen Oxides; Organometallic Compounds; Organosilicon Compounds; Phosphorus; Phosphorus Compounds; Silicon

Our studies showed that the spin-labeled (SL) compounds (free stable nitroxyl radical derivatives) accumulate predominantly in pigment melanoma and some of them possess high antimelanoma activity (100% curability of tumor bearing animals) and lower general toxicity. Taking into account our results we describe a proposed mechanism of the spin-labeled accumulation in melanoma, their antimelanoma activity and lower toxicity.

Topics: Antineoplastic Agents; Humans; Melanoma; Models, Chemical; Models, Theoretical; Nitrogen Oxides; Nitrosourea Compounds; Pigments, Biological; Silicon; Spin Labels; Triazenes; Tumor Cells, Cultured