Silica gel 70 230 mesh

Column chromatography was conducted using 70–230 mesh silica gel (Merck, Darmstadt, Germany). Watchers^® Silica gel Si 60 (70–230 mesh) was used for column chromatography (Isu Industry Co., Seocho, Korea). TLC analysis was carried out on precoated silica gel 60 F254 plates (Merck). Detection of spots on the TLC plate was performed by observation under a UV lamp (Spectroline, model CM-24A, Spectronics Corp., New York, NY, USA) or by spraying 10% aqueous H₂SO₄ on the developed plate followed by heating. Prep LC was performed with a YMC LC-Forte/R (YMC, Kyoto, Japan). NMR spectra were recorded on a Bruker Ascend 400 and Avance 500 (Bruker, Rheinstetten, Germany). High-resolution electrospray ionization mass spectrometry (HR-ESI-MS) was carried out using a SYNAPT G2 electrospray mass spectrometer (Waters, Elstree, UK) at the Korean Basic Science Institute, Seoul, Korea.

All glassware used was dried thoroughly in an oven, assembled hot, and cooled under a stream of dry nitrogen prior to use. All reactions and manipulations of air- and moisture-sensitive materials were carried out using standard techniques for the handling of such materials. All chemicals were commercial products of the highest purity which were further purified before use by using standard methods. HBpin, aldehydes, ketones, and alkenes were purchased from Aldrich Chemical Company, Alfa Aesar, and Tokyo Chemical Industry Company (TCI). ¹H NMR spectra were measured at 400 MHz with CDCl₃ as a solvent at ambient temperature unless otherwise indicated and the chemical shifts were recorded in parts per million downfield from tetramethylsilane (δ = 0 ppm) or based on residual CDCl₃ (δ = 7.26 ppm) as the internal standard. The coupling constants (J) are reported in hertz. Analytical thin-layer chromatography (TLC) was performed on glass precoated with silica gel (Merck, Rahway, NJ, USA, silica gel 60 F₂₅₄). Column chromatography was carried out using 70–230 mesh silica gel (Merck) at normal pressure. GC analyses were performed on a Younglin Acme 6100M and 6500 GC FID chromatography, using an HP-5 capillary column (30 m). All GC yields were determined with the use of naphthalene as the internal standard and the authentic sample.

¹H- and ¹³C-NMR spectra were measured using a JEOL JUM ECP-400 spectrometer (Jeol, Tokyo, Japan) at 400 MHz for ¹H-NMR and 100 MHz for ¹³C-NMR, with the compounds dissolved in deuterated dimethyl sulfoxide (DMSO-d₆) and chloroform (CDCl₃). Column chromatography was carried out using 70–230 mesh silica gel (Merck, Darmstadt, Germany). Thin-layer chromatography (TLC) was performed on pre-coated Merck Kiesel gel 60 F₂₅₄ plates (0.25 mm), and 25% H₂SO₄ was used as a spray reagent. All solvents for column chromatography were of reagent grade and were acquired from commercial sources.