Silica gel 60 f254 aluminum sheet

All chemicals used in the syntheses were purchased either from Merck Chemicals (Merck KGaA, Darmstadt, Germany) or Sigma-Aldrich Chemicals (Sigma-Aldrich Corp., St. Louis, MO, USA). The reactions and the purities of the compounds were observed by thin layer chromatography (TLC) on silica gel 60 F254aluminum sheets obtained from Merck (Darmstadt, Germany). Melting points of the synthesized compounds were recorded by MP90 digital melting point apparatus (Mettler Toledo, Ohio, USA) and were presented as uncorrected. ¹H NMR and ¹³C NMR spectra were recorded by a Bruker 300 MHz and 75 MHz digital FT-NMR spectrometer (Bruker Bioscience, Billerica, MA, USA) in DMSO-d₆, respectively. In the NMR spectra, splitting patterns were designated as follows: s: singlet; d: doublet; t: triplet; m: multiplet. Coupling constants (J) were reported as Hertz. LC-MS-MS studies were performed on a Schimadzu, 8040 LCMSMS spectrophotometer (Shimadzu, Tokyo, Japan).

All starting reagents/chemicals and dry solvents of commercial quality were purchased from the commercial suppliers VWR Darmstadt/Germany, Acros, Geel/Belgium, Alfar Aesar, Ward Hill/U.S.A., Sigma-Aldrich, St. Louis/USA, Fluka, München/Germany and Carl Roth, Karlsruhe/Germany. ¹H-NMR and ¹³C-NMR spectra were recorded on a Bruker AMX 250 (250 MHz), a Bruker AMX 300 (300 MHz) or a Bruker AMX 400 (400 MHz) spectrometer (Bruker, Germany). ¹H-NMR data are reported in the following order: chemical shift (δ) in ppm downfield from tetramethylsilane as internal reference; multiplicity (br, broad; s, singlet; d, doublet; t, triplet; q, quartet; quin, quintet; m, multiplet); approximate coupling constants (J) in Hertz (Hz). ESI-MS was performed on a Fisons Instruments VG Platform II (Manchester, Great Britain) in positive polarity. Data (m/z) are listed as mass number (M+H⁺) and relative intensity (%). MALDI_MS was performed on Voyager DE STR (Per Septive Biosystems). High Resolution Mass Spectrometry (HRMS) was carried out on a Thermo Scientific MALDI LTQ XL Orbitrap (Waltham, USA). Thin layer chromatography was performed on silica gel 60 F₂₅₄ aluminum sheets (Merck, Germany). Preparative column chromatography was performed on silica gel 63–200 μM (Merck, Germany). Melting points were determined on a Büchi B510 melting point apparatus (Büchi, Switzerland).

Melting points were measured on an XT-4 apparatus (Taike Corp., Beijing, China) and were uncorrected. IR spetra were measured on a Nexus 870 FT-IR spectrometer (Thermo Fisher Scientific, Waltham, MA, USA), and the absorption bands were expressed in cm⁻¹. The HRMS spectra were recorded on a high-resolution mass spectrometer equipped with electrospray (ESI) and nanospray sources, and a quadrupole-time of flight hybrid analyzer (Q-TOF Premier/nanoAquity, Waters, Milford, MA, USA). ¹H and ¹³C NMR spectra were obtained in CDCl₃ on a Bruker DRX-600 NMR spectrometer (Billerica, MA, USA) using TMS as internal standard. Reactions and the resulted products were monitored by TLC which was carried out on TLC Silica gel 60 F₂₅₄ Aluminum sheets from Merck KGaA, Darmstadt, Germany, and visualized in UV light (254 nm). Silica gel (300–400 mesh) for column chromatography was purchased from Qingdao Marine Chemical Factory (Qingdao, China). The reagents (chemicals), all being of A.R. grade, were purchased from Shanghai Chemical Reagent Company (Shanghai, China) and Energy Chemical (Shanghai, China). Ursolic acid (95%) was bought from Jingzhu Biological Technology Co., Ltd. (Nanjing, China).