Reveleris x2 system

Normal column chromatography was performed with silica gel (particle size: 40–60 µm) from Merck. Automatic column chromatography (MPLC, medium-performance liquid chromatography) was carried out with a Büchi Reveleris X2 system and purchased columns. Polar compounds and final products were purified via a preparative reverse-phase HPLC (RP-HPLC, Thermo Separation Products) consisting of a degasser, a pump (P4000), a Hypersil gold column (8 μm, 250 × 21.2 mm cartridge; Thermo Fisher Scientific) and a UV detector (UV1000). The gradients were chosen depending on the compound with eluents A (water/ACN/TFA, 94.9:5:0.1) and B (ACN/water/TFA, 94.9:5:0.1).

Commercial reagents and anhydrous solvents were used without further purification. Flash chromatography was performed on the Reveleris^® X2 system, Buchi. ¹H-NMR and ¹³C-NMR spectra were obtained using a Bruker Avance spectrometer at 400 MHz proton frequency (AV-III-HD, 400, Rheinstetten, Germany). All data were processed with TOPSPIN (version 3.5pl5, Bruker Biospin, Spring, TX, USA) software. Conventional abbreviations used for signal shape are as follows: s, singlet; d, doublet; dd, doublet of doublets; t, triplet; m, multiplet. LC-MS analysis (1260 Infinity Series HPLC, 6120 Quadrupole MSD, Agilent Technologies Inc.; Richardson, TX, USA) was carried out with the use of a reverse phase column, Zorbax RX-C8 (5 µm, 250 × 4.6 mm, Agilent Technologies, Santa Clara, CA, USA), maintained at 40 °C. Chromatograms were integrated and analyzed using OpenLAB Chemstation (version M8301AA, Revision C.01.07 Agilent Technologies Inc., Richardson, TX, USA). Mobile phase A was water, mobile phase B was acetonitrile and mobile phase C was glacial acetic acid. The mobile phases A, B and C were mixed at a ratio of 67.5:25.0:7.5 (v/v).