Chemicals were obtained from abcr GmbH, Acros Organics, BLDpharm, Carbolution Chemicals, Sigma-Aldrich, TCI Chemicals or VWR and used without further purification. Technical grade solvents were distilled prior to use. For all HPLC purposes and reversed phase flash chromatography, acetonitrile in HPLC-grade quality (HiPerSolv CHROMANORM, VWR) was used. Water was purified with a PURELAB flex® (ELGA VEOLIA).