Isolation and Characterization of Acid Natural Products

All chemicals were obtained from Merck or Sigma-Aldrich. The chemical reaction was monitored using thin-layer chromatography (TLC) using silica gel 60 F254-pre-coated glass plates with a thickness of 0.25 mm and a UV lamp to visualize the plate. Column chromatography was performed using silica gel (230–400 mesh). Optical rotations of the final compounds were measured with a Jasco P-2000 digital polarimeter. The infrared (IR) spectra were obtained with a Jasco FT/IR-4000 FTIR spectrometer. The NMR spectra were recorded on commercial instruments (Bruker AV 500 FT-NMR spectrometer). Low-resolution and high-resolution mass spectra were performed using Fourier-transfer mass spectrometry (FT-MS). Mass spectra were recorded in both positive modes with Bruker APEX II (National Sun Yat-sen University). Acid natural products were isolated from Prof. Tian-Shung Wu’s lab (Tainan, NCKU, Taiwan) [25 (link),27 (link),32 (link),33 (link)].