Dip 370 digital

Optical rotations were measured at 25 °C with a JASCO Dip-370 digital polarimeter using MeOH as solvent. UV spectra were recorded in MeOH using a Shimadzu UV-1601 UV–Vis spectrometer. ECD spectra were recorded in MeOH on a Jasco 810 spectrometer at 25 °C, using a quartz cell with 1.0 mm optical path length. The 1D and 2D NMR spectra were recorded on a Bruker Avance III 400 NMR instrument at 400 MHz for ¹H NMR and 100 MHz for ¹³C NMR. Chemical shift values (δ) are given in parts per million (ppm), and the coupling constants are in Hz. Low-resolution and high-resolution MS were recorded on Shimadzu LCMS-QP8000α and Agilent G6224A TOF mass spectrometers, respectively. Normal phase column chromatography was performed using Baker silica gel 40 μm flash chromatography packing (J.T. Baker) and reversed phase chromatography was carried out using BAKERBOND C₁₈ 40 μm preparative LC packing (J.T. Baker). Analytical and preparative thin-layer chromatography (TLC) were performed on pre-coated plates (0.20 mm thickness) of silica gel 60 F₂₅₄ (Merck) and RP-18 F_254S (Merck). The HPLC purifications were carried out on a Phenomenex Luna 5 μm C₁₈ column (10 × 250 mm) with a Waters Delta Prep system consisting of a PDA 996 detector. The MM2 energy minimizations of possible conformations of compounds were performed using Chem3D 15.0 from PerkinElmer Inc.