|Ph.D Student||Ruderfer Ilya|
|Subject||Synthesis of Silicon Containing Amino Acids and Proteins|
via Novel Alpha-Aminosilylithiums
|Department||Department of Chemistry||Supervisor||? 18? Yitzhak Apeloig|
|Full Thesis text|
All known life on Earth is based on carbon-based compounds. Astrobiologists believe that silicon is a good candidate to be a building block of life in conditions different from those on Earth, especially in environments with no oxygen. However, we do not have to go to outer space or to science-fiction literature to find silicon in biological systems. Carbon compounds interact with silicon in a variety of marine species, such as radiolarians, sponges, and diatoms, which use carbon-based enzymes to produce protective silica exoskeleta. Organosilicon compounds, that are all non-natural, are also making their first steps as bioactive agents in agricultural and pharmaceutical applications and their role may become increasingly significant in the future.
Can one imagine "life molecules" based on silicon? Amino acids, peptides, and proteins are essential molecules in all known life forms. In all previous studies silylation of the side chains of amino acids and peptides was studied. The aim of my research was radically different i.e. to produce the first a-sila-peptides in which the alpha-carbon is substituted by a silicon atom.
In my research the first known protected a-sila-amino acid, and the derived protected dipeptides, - in which a silicon atom is integrated in the a-position were prepared. This is certainly the main achievement and novel aspect of this thesis. We also prepared the protected a-sila-peptide analogue that contains a natural amino acid (proline) bonded by a peptide bond to a hypersilyl residue, and studied some aspects of its biological activity.
The new a-sila-amino acid and a-sila-peptides were prepared from a novel a-amino-substituted hypersilyllithium compound. This novel functionalized silyllithium was prepared by a new synthetic route, i.e. via lithiation of the corresponding silylmercury compound . This synthetic pathway made it possible, for the first time, to prepare and isolate amino-substituted silyllithium in a non-solvated-aggregated form.
a-Amino-substituted silyllithiums and silylmercury compounds are an excellent starting point for studying amino-substituted silenes and amino-substituted silyl radicals. These low-coordination silicon compounds are interesting in their on right and they can also play an important role in the photochemistry of silapeptides.
The irradiation of amino-substituted silylmercury compounds led to the generation of previously unknown amino-substituted silyl radicals that were observed by EPR spectroscopy. a-aminosilyllithium was used in synthesis of potential precursors for the amino-substituted silenes, however, our attempts to prepare from them amino-substituted silenes failed.