Mcp 200

Optical rotations were measured using an MCP 200 (Anton Paar, Shanghai, China) polarimeter. UV spectra were recorded on a Shimadzu UV-240 spectrophotometer (Shimadzu, Kyoto, Japan). The Chirascan-plus circular dichroism spectrometer (Applied Photophysics Ltd., Surrey, UK) was used for recording ECD spectra. IR spectra were recorded by a Fourier transformation infra-red spectrometer coupled with infra-red microscope EQUINOX 55 (Bruker, Rheinstetten, Germany). The 1D and 2D NMR spectra were recorded on Bruker Avance 400 spectrometer (¹H 400 MHz, ¹³C 100 MHz). Chemical shifts (δ) were given in ppm with reference to the solvent signal (δ_C 39.52/δ_H 2.50 for DMSO), and coupling constants (J) were given in Hz. HR-ESIMS spectra were recorded on an LTQ-Orbitrap LC-MS spectrometer (Thermo Corporation, Waltham, MA, USA). ESIMS spectra were obtained on an ACQUITY QDA LC-MS spectrometer (Waters Corporation, Milford, MA, USA). Column chromatography (CC) was performed using silica gel (200–300 mesh, Qingdao Marine Chemical Factory, China) and Sephadex LH-20 (GE Healthcare, Littile Chalfont, UK) as stationary phases. HPLC was performed on an Essentia LC-16 (Shimadzu, Shanghai, China). Pre-coated silica gel plates (Qingdao Huang Hai Chemical Group Co., G60, F-254, China) were used for thin layer chromatography.

Optical rotation values were recorded on a PerkinElmer 241 or Anton Paar MCP 200 polarimeter. The specific rotation is calculated as follows: ${\left[\alpha \right]}_{\lambda }^{\phi }=\left[\alpha \right]\cdot 100\cdot c^{-1}\cdot d^{-1}$ . The wave length λ is reported in nm (sodium D line, λ = 589 nm), the measuring temperature ϕ in °C; α represents the recorded optical rotation, c the concentration of the analyte in g mL⁻¹, and d the length of the cuvette in dm. Thus, the specific rotation is given in 10⁻¹ deg cm² g⁻¹. The values for the specific rotation are reported as follows: specific rotation (concentration g 100 mL⁻¹; solvent).