Jascop650 spectrometer

Optical rotations were measured on P2000 polarimeter (JASCO, Tokyo, Japan). UV spectra were obtained on a JASCOP650 spectrometer (JASCO). IR spectra were recorded on a Nicolet 5700 FT-IR microscope instrument (FT-IR microscope transmission, Thermo Electron Corporation, Madison, WI, USA). 1D and 2D NMR spectra were acquired at 500 or 600 MHz for ¹H and 125 or 150 MHz for ¹³C, respectively, on Varian INOVA 500 MHz, or Bruker AVANCE III HD 600 MHz (Bruker Corporation, Karlsruhe, Germany), in acetone-d₆ or methanol-d₄, with solvent peaks as references. ESI-MS and HR-ESI-MS data were measured using an AccuToFCS JMST100CS spectrometer (Agilent Technologies, Ltd., Santa Clara, CA, USA). Column chromatography (CC) was performed with silica gel (200–300 mesh, Qingdao Marine Chemical Inc., Qingdao, China). HPLC separation was performed on an instrument consisting of a Waters 515 pump and a Waters 2487 dual λ absorbance detector (Waters Corporation, Milford, MA, USA) with a YMC semi-preparative column (250 × 10 mm i.d.) packed with C18 (5 μM). TLC was carried out with glass precoated silica gel GF254 plates (Qingdao Marine Chemical, Inc., Qingdao, China). Spots were visualized under UV light or by spraying with 7% H₂SO₄ in 95% EtOH followed by heating.