Avance 3 500 m nmr spectrometer

The optical rotations were detected at 20°C using MCP 5100 digital polarimeter (Anton Paar, Graz, Austria). The UV data were recorded on a Shimadzu UV-2500 spectrophotometer (Shimadzu, Kyoto, Japan). The Chirascan CD spectrometer (Applied Photophysics Ltd., Surrey, UK) was used to acquire ECD spectra. 1D and 2D NMR spectra were recorded on a Bruker AVANCE III 500 M NMR spectrometer (Bruker BioSpin Corporation, Billerica, USA). UPLC-Q-TOF/MS analysis was carried out on a Waters ACQUITY UPLC system (Waters Corporation, Milford, USA) equipped with an AB SCIEX Triple TOF 5600 mass spectrometer with electrospray ionization source (ESI; Framingham, MA, USA). Silica gel (200–300 mesh, Qingdao Marine Chemical Inc., Qingdao, China), RP-C₁₈ silica gel (Merck KGaA, Darmstadt, Germany), and Sephadex LH-20 gel (GE Healthcare Bio-Sciences AB, Uppsala, Sweden) were employed for column chromatography (CC). High-performance liquid chromatographies (HPLCs) were performed on Agilent 1260 series (Agilent Technologies, Santa Clara, USA) with C₁₈ reversed-phase columns (YMC, Kyoto, Japan; 250 × 4.6 mm i.d., 5 μm, for analysis; 250 × 10 mm i.d., 5 μm, for separation).