[60]Fullerene Hybrids Bearing “Steroid Wings”: A Joined Experimental and Theoretical Investigation

Novel [60]fullerene-steroid hybrids have been synthesized by Bingel-Hirsch cyclopropanation reaction between C(60)and steroid malonates, leading to conjugates in which a [60]fullerene unit is connected to one or two dehydroepiandrosterone moieties, an important naturally occurring steroid hormone. The obtained derivatives have been fully characterized by a whole set of instrumental techniques in order to determine their chemical structure. Moreover, their electrochemical properties, investigated by cyclic voltammetry, revealed the presence of three reversible reduction waves for both hybrids. Furthermore, Transmission Electron Microscopy studies allowed to determine the morphology and size of the fullerene hybrids in aqueous solution, showing a tendency to organize into spherical nanoscale structures. Theoretical calculations using the DFT-PBE method and 6-311G(d,p) basis set, were performed to predict the most stable conformations for the synthesized compounds, and to determine the factors that control the geometry of these hybrid molecules. In addition, parameters such as polarity, and lipophilicity were estimated. The obtained results corroborate the predicted activity against HIV-1 protease as suggested by molecular docking simulation.