|M.Sc Student||Pogoreltsev Alla|
|Subject||Corannulene Derivatives as Building Blocks for Chemical|
|Department||Department of Chemistry||Supervisor||PROFESSOR EMERITUS Ehud Keinan|
The notion that supramolecular containers can be created by total synthesis and self-assembly of small sub-units is largely inspired by the architecture of virus particles, particularly the spherical viral capsids. The shell of these viruses has an icosahedral symmetry and it is formed from many small protein subunits that are held together by weak interactions, such as hydrogen bonds, hydrophobic and electrostatic interactions. A general synthetic strategy for constructing stable containers of icosahedral symmetry, built from non-protein molecular building blocks, has been proposed in our laboratory. Such capsids can be formed by self-assembly of symmetric corannulene-based pentagonal building blocks. Our proposed general strategy is to design and synthesize pentagonal tiles with the appropriate "sticky" edges and find the appropriate conditions for their self-assembly to the stable icosahedral capsid.
The corannulene molecule was chosen as a skeleton core for the total synthesis of such pentagonal tiles, because it has a rigid five-fold symmetric scaffold with a suitable curvature. In order to construct icosahedral structures, the building blocks should be attached to one another by thermodynamically stable but kinetically labile bonds. This will allow fast equilibration between different structures, pushing the reaction from the kinetic products and other local minima towards the global free energy minimum of the icosahedral capsid. Hydrogen bonding was chosen as a suitable binding mechanism between the pentagonal edges.
Corannulene was prepared by using the improved literature multi-step procedure. Subsequently, it was chlorinated to give the symmetric 1,3,5,7,9-pentachlorocorannulene, a starting material for functionalization of the corannulene core. 1,3,5,7,9-pentachlorocorannulene was converted to various novel alkoxy-corannulene derivatives, such as symmetric 1,3,5,7,9-pentamethoxycorannulene, through copper-mediated Ullmann Condensation reactions. Bromination and chlorination reactions on the penta-methoxycorannulene produced deca-substituted corannulenes bearing symmetrically two different functional groups. These achievements provide interesting opportunities for the further synthesis of new pentagonal tiles for capsid formation.