General synthetic procedures. Unless stated otherwise, all reactions were performed without air-or moisture-sensitivity precautions, and were stirred with Teflon-coated magnetic stir bars. For work under inert gas (nitrogen) atmosphere, a Schlenk apparatus equipped with a liquid nitrogen trap and a high vacuum pump from Vacuubrand were used. For solvent evaporation a Heidolph Laborota 400 equipped with a vacuum pump was used. Flash column chromatography was conducted under positive nitrogen pressure over Merck Ceduran® Si 60 silica gel as stationary phase. TLC control, extractions and column chromatography were conducted using distilled, technical grade solvents.