Model 341

A PerkinElmer Model 341 polarimeter was applied to measure optical rotations. ECD spectra were acquired using a Chirascan V100 spectropolarimeter. NMR data were recorded at 400 or 600 MHz (Bruker AVANCE). HRESIMS spectra were obtained on a ThermoFisher mass spectrometer (LTQ Orbitrap XL). Size-exclusion chromatography was conducted with Sephadex LH-20. Column chromatography (CC) was applied using silica gel which was produced by Anhui Liangchen Co., Ltd.

Optical rotations were measured at ambient temperature for solution in CHCl₃ with a Perkin–Elmer automatic polarimeter, Model 341. Melting points were measured on a Kofler hot stage. All reactions were monitored by thin-layer chromatography (TLC) on silica gel 60 coated glass slides. Spots were visualized by charring with 5% H₂SO₄ in ethanol, 1% ninhydrine in ethanol, or UV light, as required. Column chromatography was performed by elution from prepacked (Biotage, Inc.) columns of silica gel with a Isolera Flash Chromatograph (Biotage), the latter being connected to an external Evaporative Light Scattering Detector, Model 380-LC (Varian, Inc.). Nuclear Magnetic Resonance (NMR) spectra were measured at 600 MHz for ¹H, and 150 MHz for ¹³C with Bruker Avance spectrometers. Solvent peaks were used as internal references relative to TMS for ¹H and ¹³C chemical shifts (ppm). Assignments of NMR signals were made by homonuclear and heteronuclear two-dimensional correlation spectroscopy, run with software supplied with the spectrometers. Liquid Chromatography–Electron Spray-Ionization Mass Spectrometry (ESI-MS) was performed with a Hewlett–Packard 1100 MSD spectrometer. Solutions in organic solvents were dried with anhydrous Na₂SO₄, and concentrated at 40°C/2 kPa.