P 2000 polarimeter

Diaion HP-20 resin (Mitsubishi Chemical Industries, Ltd., Tokyo, Japan), Sephadex LH-20 gel (GE Healthcare, Stockholm, Sweden), silica gel (230–400 mesh, Merck, Kenilworth, MA, USA), and LiChroprep RP-18 gel (40–63 mm, Merck) were used for open CC. Fractions were monitored by TLC analyses on silica gel 60 F₂₅₄ (Merck) and RP-18 F_254S (Merck) plates. MPLC (Teledyne Isco, Lincoln, NE, USA) was used for further fractionation with pre-packed Redi Sep-Silica (12 g, 24 g, 40 g, Teledyne Isco) and Redi Sep-C18 cartridges (26 g, 43 g, 80 g, Teledyne Isco). Preparative HPLC was performed using a HPLC purification system (1525 pump and PDA 1996 detector, Waters Corp., Milford, MA, USA) with a Gemini NX-C18 110A (250 × 21.2 mm i.d., 5 μm, Phenomenex, Torrance, CA, USA) or YMC-pack ODS-A columns (250 × 20.0 mm i.d., 5 μm, YMC Co., Ltd., Kyoto, Japan). UV and FT-IR spectra were recorded using OPTIZEN UV–Vis and Agilent Cary 630 FT-IR (Agilent Technologies, Santa Clara, CA, USA) spectrophotometers, respectively. Optical rotations were measured using a JASCO P-2000 polarimeter; NMR spectra were acquired by JEOL (JEOL, Tokyo, Japan) at 500 MHz; and HR-DART-MS spectra were obtained by the DART ion source (Ionsense, Tokyo, Japan) coupled to an AccuTOF-TLC (JEOL). Finally, the circular dichroism spectra were measured by a Chirascan-plus spectrometer (Applied Photophysics Ltd., Leatherhead, UK).