Analytical automatic polarimeter

Optical rotations were measured on a Rudolph Research Analytical automatic polarimeter, and UV data were obtained on a Shimadzu Biospec-1601 spectrophotometer (Shimadzu, Kyoto City, Kyoto Prefecture, Japan). CD spectra were recorded on a JASCO J-815 spectropolarimeter (Jasco, Essex, UK). IR data were recorded using a Nicolet Mag 750 spectrophotometer (Waltham, MA, USA). ¹H and ¹³C NMR data were acquired with Bruker Avance III-600 spectrometer (Burker, Billerica, MA, USA) using solvent residual signals (Acetone-d₆: δ_H 2.05/δ_C 29.8, 206.1) as references. The heteronuclear single quantum coherence (HSQC) and HMBC experiments were optimized for 145.0 and 8.0 Hz, respectively. Electrospray ionization tandem mass spectrometry (ESIMS) and HRESIMS data were obtained using an Agilent Accurate-Mass-Q-TOF LC/MS G6550 instrument equipped with an electrospray ionization (ESI) source (Agilent, Santa Clara, CA, USA). All MS experiments were performed in the positive ion mode. Semi-preparative HPLC separation was performed on a Shimadzu LC-6AD instrument packed with a YMC-Pack ODS-A column (5 µm, 250 mm × 10 mm) (Shimadzu, Kyoto City, Kyoto Prefecture, Japan). Sephadex LH-20 was purchased from Pharmacia Biotech (Uppsala, Sweden). Silica gel (200–300 mesh) for column chromatography was produced by Qingdao Marine Chemical Factory, Qingdao, China.