Mercury plus spectrometer

All necessary reagents and solvents were available from Sigma-Aldrich (St. Louis, MO, USA) or TCI chemicals and the reagents (Tokyo, Japan) were used without further purification and the solvents were handled in a moisture-free atmosphere. (+)-(18-Crown-6)-2,3,11,12-tetracarboxylic acid was obtained from RS tech (Daejeon, Korea). The purification of compounds was performed by using column chromatography (silica gel, Merck Kieselgel 60, 70–230 mesh ASTM). The nuclear magnetic resonance (NMR) spectra of the compounds were recorded with Varian Mercury Plus spectrometer (300 MHz). Liquid chromatography was performed with an HPLC system consisting of a Waters model 515 HPLC pump (Milford, MA, USA), a Rheodyne model 7725i injector (Rohnert Park, CA, USA) with a 20 μL sample loop, a YoungLin M720 absorbance UV detector (variable wavelength, Seoul, Korea) and a YoungLin Autochro data module (Software: YoungLin Autochro-WIN 2.0 plus). The temperature of the chiral column was controlled by using a Julabo F30 Ultratemp 2000 cooling circulator (Seelbach, Germany). Racemic and optically active analytes were available from a prior study or prepared using the similar reported procedure [29 (link),30 (link)]. Injection samples were prepared by dissolving each of racemic and optically active samples in methanol (usually 2.5 mg/mL). The usual injection volume was 5.0 µL.

A caffeic acid was purchased by Sigma Aldrich (Sigma-Aldrich, St. Louis, MO, USA). All other chemicals used in the synthesis were obtained from commercial supplier (Merck, Darmstadt, Germany) and were of p.a. purity. ¹H-, ¹³C-, and ³¹P-NMR spectra were measured on a MERCURY plus spectrometer (Varian, Palo Alto, CA, USA), working at frequencies of 300, 75, and 121.5 MHz, respectively. ¹³C- and ³¹P-NMR spectra were coupled against protons. The spectra were measured in CDCl₃. The chemical shifts were referenced with respect to an internal TMS (δ ¹H = 0, δ ¹³C = 0) or 85% H₃PO₄ (δ ³¹P = 0 for ∈ ³¹P = 40.4807420 MHz) signal.

¹H NMR (400 MHz) and ¹³C NMR (100 MHz) spectra were measured in CDCl₃ or DMSO-d₆ on a Varian Mercury Plus spectrometer. Chemical shifts (δ) are reported in ppm downfield from TMS as internal standard, and coupling constants (J) are given in hertz (Hz). Melting points were determined on a Kofler micro melting point apparatus and are uncorrected. Infrared spectra were recorded on an Avatar FT-IR 6700 (Thermo Scientific, UK) using an attenuated total reflectance (ATR) method in the range 4000–400 cm⁻¹. Microanalyses were performed with a Perkin-Elmer, CHN 2400 elemental analyzer. The progress of chemical reactions was monitored on TLC-sheets ALUGRAM^® SIL G/UV₂₅₄ (Macherey-Nagel, Dueren, Germany). Detection was carried out with ultraviolet light (254 nm). Column chromatography was performed on silica gel, Kieselgel 60 Merck Type 9385 (0.040–0.063). All commercial reagents were used in the highest available purity without further purification.

A Sanyo Gallenkamp (UK) melting point apparatus was used to find the melting points. Optical rotations were measured on a JASCO P-1020 digital polarimeter (Japan). The UV spectra were obtained on an Agilent 8453 UV-visible spectrophotometer (Germany). A PerkinElmer Spectrum One FT-IR spectrophotometer (USA) was used to acquire the IR spectra. NMR spectra were collected at 400 MHz (¹H) and at 100 MHz (¹³C) using a Varian Mercury Plus spectrometer (USA). HRESIMS was performed on a Micromass Q-TOF 2 hybrid quadrupole time-of-flight (Q-TOF) mass spectrometer (Micromass, UK). Analytical thin-layer chromatography (TLC) was accomplished on Merck silica gel 60 F₂₅₄. Column chromatography separations were carried out on silica gel less than 0.063 mm, 0.063–0.200 mm or RP-18.