6530b accurate mass qtof mass spectrometer

Madecassic acid (1) was purchased from Santa Cruz Biotechnology Inc., in over 95% purity. Other reagents and solvents were purchased from Sigma-Aldrich Co., Merck Co., and VWR Portugal and used without further purification. Solvents were dried over standard drying agents according to the usual procedures. Thin-layer chromatographic (TLC) analysis and preparative TLC were carried out on Kieselgel 60HF254 and Kieselgel 60HF254/Kieselgel 60G from Merck Co., respectively. Column chromatographic separations were performed using Kieselgel 60 (230–400 mesh) from Merck Co. Melting points were determined by using open capillary tubes on a Büchi B-540 melting point apparatus and are uncorrected. ¹H, ¹³C, DEPT-135, HSQC, and HMBC NMR experiments were performed in CDCl₃ or C₆D₆ and recorded on Bruker Avance 400 and Bruker Avance III spectrometers operating at 400 and 600 MHz for ¹H and 100 and 150 MHz for ¹³C, respectively. The Bruker Avance III NMR spectrometer was equipped with a 3 mm cryogenically cooled probe. Spectra were calibrated to residual solvent signals at δ_H 7.26 and δ_C 77.16 (CDCl₃) and δ_H 7.16 and δ_C 128.06 (C₆D₆). IR spectra were recorded on a PerkinElmer Spectrum 2000 FT-IR spectrometer using NaCl circular cell windows. HRESIMS were performed with an Agilent 6530B Accurate Mass QTOF mass spectrometer.