Merck silica gel 60 pf254

Melting points were determined with a Yanaco model MP microscope (Yanaco, Tokyo, Japan). Column chromatography was carried out using silica gel 60 N (Kanto Chemical, Tokyo, Japan). Thin layer chromatography (TLC) was carried out on a Merck silica gel 60 PF₂₅₄ (Merck, Tokyo, Japan). IR spectra were obtained on FT/IR-410 spectrometer (JASCO, Tokyo, Japan) as neat films between NaCl plates, or KBr pellets. NMR spectra were recorded on JEOL EX-400 spectrometer (JEOL, Tokyo, Japan). ¹H-NMR spectra were obtained at 400 MHz as dilute solution in CDCl₃, and the chemical shifts were reported relative to internal TMS. Low-resolution mass spectra were recorded at ionizing voltage of 70 eV by electron impact. High-resolution mass spectra were recorded on Exactive Orbitrap LC-MS (Thermo-Fischer, Yokohama, Japan). UV/vis spectra were recorded on JASCO V-650DS spectrometer (JASCO, Tokyo, Japan) in MeOH. UV irradiation was performed using a 450 W high-pressure mercury lamp (USHIO UM453, Tokyo, Japan). Visible-light irradiation was performed using a 250 W high-pressure mercury lamp (ASAHI SPECTRA REX-250, Tokyo, Japan) through quartz fibers with a UV-cut filter.

Optical rotations were measured with a JASCODIP-1000 digital polarimeter (JASCO Inc., Tokyo, Japan). UV and ECD spectra were recorded using a JASCO J-810 apparatus. IR analyses were performed using a Bruker Tenser 27 spectrophotometer (Bruker, Karlsruhe, Germany). NMR spectra were recorded on a Varian Mercury Plus 400 spectrometer (Varian Inc., Palo Alto, CA, USA) or on a Bruker Avance 400 NMR spectrometer (Bruker, Karlsruhe, Germany) using CDCl₃, CD₃OD and CD₃CN as solvents. The residual peaks of these solvents were used as internal references. The HRESITOFMS were carried out on a Bruker micrOTOF mass spectrometer (Brucker, Karlsruhe, Germany). Column chromatography was carried out on MERCK silica gel 60 (230–400 mesh) (Merck, Darmstadt, Germany). Thin-layer chromatography was carried out with pre-coated MERCK silica gel 60 PF254 (Merck, Darmstadt, Germany); the spots were visualized under UV light (254 and 365 nm) and further stained by spraying p-anisaldehyde and then heated until charred.