Ultrashield 400 mhz nmr spectrometer

Fraction B and Fraction D were analyzed by ¹H-NMR, which was recorded on a spectrometer (JEOL-ECA600, 600 MHz, JEOL, Tokyo, Japan) using DMSO-d6 as solvents and tetramethylsilane (TMS) as internal standard. Chemical shifts and J values are given in Hz. The ¹³C-NMR spectra of Fraction D were also recorded using a Bruker UltraShield 400 MHz NMR spectrometer (Bruker Corporation, Billerica, MA, USA). All samples were dissolved in DMSO-d₆ and measured (2 mg/0.7 mL for ¹H-NMR, 20 mg/0.7 mL for ¹³C-NMR). Furthermore, the structure was comprehensively determined by FT-IR and electrospray ionization mass spectrometry (ESI-MS) measurements. ESI-MS spectra were acquired using an Esquire 3000 plus instrument (Agilent Technologies, Inc., Santa Clara, CA, USA). The ESI-MS conditions were as follows: positive or negative ion mode, injection flow rate of 2 μL/min, drying gas (nitrogen) flow rate of 4 L/min, nebulizer pressure of 10 psi (equivalent to 29.3 kgf/cm²), drying gas temperature of 300 °C, and a mass scan range of 50–1000 m/z. FT-IR/IRT-3000 ATR-30-Z (JASCO) was used for identification. Attenuated Total Reflection (ATR) was performed by placing a powder sample over the entire surface of the ATR crystals and then pressing the sample firmly against the prism while compressing it. The measuring range was 400–4000 cm⁻¹.

The UV spectrum was obtained on a SCINCO Spectrometer, and IR spectrums were recorded on a Nicoler Auatar Spectrometer series FT360 spectrophotometer. NMR spectra (1D and 2D) were recorded on a Bruker Ultrashield–400 MHz NMR spectrometer (Karlsruhe, Germany). Mass spectra were obtained on an Agilent 6210 ESI (Electrospray Ionization)/TOF (Time of Flight) MS spectrometer (Palo-Alto, CA, USA), to obtain HRMS spectra, and on an EIMS (Electron Ion Mass Spectrum) Thermofisher ISQ spectrometer. Semi-preparative HPLC was performed on a Dionex Ultra-3000 (Sunnyvale, CA, USA) and a Waters 1525 (Milford, MA, USA) using a Cosmosil C-18 column (10 μm × 20 mm × 250 mm and 5 μm × 4.6 mm × 250 mm). CD spectra were measured on a qCD spectrometer [APL (Applied Photophysics Limited Company, Leatherhead, UK)]. Silica gel GF₂₅₄ (10–40 μm), prepared for TLC (Thin Layer Chromatography), and silica gel (200–300 mesh), for column chromatography (CC), were obtained from Qingdao Marine Chemical Factory (Qingdao, People’s Republic of China). Fractions were monitored by TLC and the spots were visualized under aultraviolet lamp at 254 nm and in an iodine cylinder.

All starting materials and solvents were bought from commercial vendors and used without further purification. Reactions were analyzed by TLC on precoated 0.20-mm-thick ALUGRAM TLC sheets with fluorescent indicator and by LC-MS performed on a Prominence Ultrafast Liquid Chromatography system (Shimadzu) equipped with a 2 × 150 mm C18 analytical column (Waters X-Bridge) coupled to an MS-2020 single quadrupole mass analyzer (Shimadzu). A linear gradient of 5 to 80% acetonitrile in water (with 0.1% formic acid [FA]) was utilized. Silica column chromatography was performed using 230 to 400 mesh silica (Kieselgel 60). NMR spectra were recorded in CDCl₃ and measured using a Bruker Ultrashield 400 MHz NMR Spectrometer. Chemical shifts are reported in ppm relative to the residual solvent peak.