Unity plus 500 nmr spectrometer

For isomerization studies, 2.5 ∙ 10^–3 m solutions of 1_s were prepared in the specified solvents. For each experiment 500 μL were transferred into an NMR tube. For studies requiring (1–H)⁺ 1.0 μL of HBF₄ ∙ OEt₂ was added. The NMR tube was subsequently fitted with a glass fiber cable for in situ irradiation and the samples were left to equilibrate at the specified temperature. To follow the protonation of 1_s 1.3 ∙ 10^–3 m solutions were used. NMR spectra were recorded on a Varian Unity Plus 500 NMR spectrometer. Chemical shifts are given in parts per million (ppm) relative to the residual solvent signal. Irradiations were performed using fiber-coupled LEDs (M395F3, M470F3, M530F2) obtained from Thorlabs Inc.

The ¹H and ¹³C NMR spectra were obtained on a Varian UNITY plus 500 NMR spectrometer operating at 500 MHz (for ¹H) and at 125 MHz (for ¹³C) using acetone-d6 containing 0.03% tetramethylsilane as an internal standard. Fractionation of constituents from the plant material was carried out by open column chromatography using Silica gel N60 (spherical 40–50 um, 11 × 4 cm, flow rate 20 mL/min, Kanto Chemical Co., Japan) and Sephadex LH-20 (590 × 10 mn, flow rate 0.2 mL/min, GE Healthcare Bio-sciences AB, Sweden), respectively. Mightysil RP-18 GP column (250 × 4.6 mm, flow rate 1.0 mL/min, Kanto Chemical Co.) was used for reverse-phase high-performance liquid chromatography (RP-HPLC, Shimadzu LC10A).