6545 accurate mass q tof lc ms

All reagents and solvents were purchased from the suppliers and used directly in the experiments. THF was dried by distillation ver sodium benzophenone. TLC was carried out using silica gel 60 pre-coated aluminium plates (0.20 mm thickness) from Macherey-Nagel (Darmstadt, Germany) with visualisation by UV light (254 nm). Flash chromatography was performed on silica gel (particle size 40–63 μm). IR spectra were recorded on a Tensor 27 spectrometer (Bruker, Ettlingen, Germany) using KBr discs. ¹H-NMR spectra were obtained from an AVANCE III 400 spectrometer (Bruker, Fällanden Switzerland). The chemical shifts, given as δ values, were quoted in parts per million (ppm); ¹H-NMR chemical shifts were measured relative to internal tetramethylsilane; Apparent coupling constants (absolute values), J, were measured in Hertz and multiplicities quoted as singlet (s), doublet (d), triplet (t), quartet (q) or combinations thereof as appropriate. Mass spectra were obtained from an 6545 Accurate-Mass Q-TOF LC/MS (Agilent Technologies, Santa Clara, CA, USA). Melting points were determined using a WRS-1B melting point measurement instrument (Shanghai, China) and were uncorrected.

Column chromatography was conducted using Silica gel 60 (70–230 mesh, Merck, Darmstadt, Germany) and Sephadex LH-20 (25–100 μm; Pharmacia, Stockholm, Sweden). Thin-layer chromatography (TLC) analysis was performed on Silica gel 60 F254 Art. 5715 plates (Merck, Germany). High-performance liquid chromatography (HPLC) preparative analysis was performed using a Gilson HPLC system equipped with two pumps (305 master pump, 307 slave pump) and a mixer (811C dynamic mixer), and a Shimadzu HPLC system with a UV/vis detector (SPD-20A), pump (LC-20AT), and system controller (CBM-20A). HPLC was conducted using a Watchers 120 ODS-BP column (S-10 μm, 150 mm × 10 mm, Isu Industry Corp., Seoul, Republic of Korea). High-resolution electrospray ionization mass spectrometry (HR-ESI-MS) was conducted using an Agilent 6530 Accurate-Mass Quadrupole Time-of-Flight (Q-TOF) LC/MS system, and a 6545 Accurate-Mass Q-TOF LC/MS (Agilent Technologies, Santa Clara, CA, USA). Nuclear magnetic resonance (NMR) spectra were recorded using JEOL 400 MHz (JNM-ECZ400S, JEOL, Tokyo, Japan), Bruker 500 MHz (Bruker, Billerica, MA, USA), and Agilent Technologies 600 MHz (Santa Clara, CA, USA) instruments. DMSO-d₆ and chloroform-d (Cambridge Isotope Laboratories, Andover, MA, USA) were used as solvents for NMR studies.