**3. Materials and Methods**

#### *3.1. General Information*

All reagents were obtained from commercial suppliers and were used without additional purification. All solvents were distilled before use. Melting points were determined by using a Boetius apparatus (VEB Analytic, Dresden, Germany) and are uncorrected. IR spectra were recorded in KBr pellets or in CHCl3 by using a Bruker Equinox 55 spectrophotometer (Bruker Optik GmbH, Ettlingen, Germany). 1H-NMR spectra were recorded on a Bruker Avance III-500 HD (500 MHz) or a Bruker Avance III-700 (700 MHz) spectrometer (Bruker Corporation, Bremen, Germany) with CDCl3 or DMSO-*d*<sup>6</sup> as the solvent and TMS as the internal standard. 13C-NMR spectra were recorded on a Bruker Avance III HD-500 spectrometer at 125 MHz or a Bruker Avance III-700 spectrometer at 176 MHz. ESI mass spectra were recorded on an Agilent 6510 Q-TOF LC/MS instrument (Agilent, Santa Clara, CA, USA). Silufol UV–Vis TLC plates (Sklarny Kavalier, Votitsa, Czech Republic) treated with HCl vapor were used for analytical TLC. Preparative TLC was performed on silica gel 60 Merck

(40–60 μm). TLC plates were developed in system A (hexane–benzene–acetone (2:1:1 *v*/*v*)), system B (hexane–benzene–acetone (2:1:2 *v*/*v*)), or system C (benzene–EtOAc–MeOH (7:4:2 *v*/*v*)).
