Thermo mat95xp

Optical rotations were measured using an Anton Paar MCP-500 spectropolarimeter (Anton Paar, Graz, Austria). The NMR spectra were recorded on a Bruker Avance-500 spectrometer (Bruker Corporation, Fällanden, Switzerland) with TMS as an internal reference. Experimental ECD spectra in MeOH were acquired in a quartz cuvette of 1 mm optical path length on an Applied Photophysics Chirascan spectrometer. HRESIMS spectra were obtained in a Thermo MAT95XP high-resolution mass spectrometer (Thermo Fisher Scientific, Bremen, Germany). Preparative HPLC was performed on an Agilent 1260 Infinity system equipped with a DAD detector using a preparative YMC ODS C₁₈ column (20 × 250 mm, 5 μm). Column chromatography was performed using silica gel (200–300 mesh, Qingdao Marine Chemical Inc., Qingdao, China) and Sephadex LH-20 gel (Pharmacia Fine Chemical Co. Ltd., Sweden). Thin-layer chromatography (TLC) was carried out on silica gel plates (Merck KGaA, Darmstadt, Germany) using various solvent systems. All solvents were purchased from Guangzhou Chemical Reagent Company, Ltd. (Guangzhou, China).

HRESIMS were measured on a Thermo MAT95XP high resolution mass spectrometer (Thermo Fisher Scientific, Bremen, Germany). Optical rotations were recorded using an Anton Paar MCP-500 (Anton Paar, Graz, Austria) and the electronic circular dichroism (ECD) measured on a Jasco 820 spectropolarimeter (Jasco Corporation, Kyoto, Japan) under N₂ gas protection. IR and UV spectra were recorded on Shimadzu IR Affinity-1 and Shimadzu UV-2600 (Shimadzu Corporation, Kyoto, Japan) spectrophotometer, respectively. NMR measurements were carried out on a Bruker Avance-500M spectrometer (Bruker, Fällanden, Switzerland) with tetramethylsilane as an internal standard. Shimadzu LC-20 AT (Shimadzu Corporation, Kyoto, Japan) equipped with an SPD-M20A PDA detector (Shimadzu Corporation, Kyoto, Japan) was adopted for semipreparative HPLC separation with YMC-pack SIL and YMC-pack ODS-A column (250 × 20 mm, 5 μm, 12 nm, YMC CO., Ltd., Kyoto, Japan). Silica gel (200–300 mesh) and Sephadex LH-20 gel were purchased from Qingdao Marine Chemical Plant (Qingdao, China) and Amersham Biosciences (Uppsala, Sweden), respectively. All solvents were of analytical grade (Guangzhou Chemical Regents Company, Ltd., Guangzhou, China).