1100 msd spectrometer

Argon and nitrogen were purchased from Linde Uruguay (Montevideo, Uruguay). Other chemicals were purchased from Sigma (St. Louis, MO), Aldrich (Milwaukee, WI) or Applichem (Germany) at the highest purity available. The tocopherol used along the study was always (±)-α-TOH (Sigma Aldrich, St. Louis, USA). Compound 1b was synthesized according to literature methods²⁷ . ¹H NMR and ¹³C NMR spectra were recorded on a Bruker DPX-400 instrument, with CDCl₃ as solvent and tetramethylsilane as the internal reference. Electron impact (EI) and electrospray (ES+) mass spectra were obtained at 70 eV on a Shimadzu GC-MS QP 1100 EX or on a Hewlett Packard 1100 MSD spectrometer, respectively. TLC was carried out on Alugram® Sil G/UV254 or aluminum oxide on polyester plates. Column chromatography (CC) was carried out on silica gel (Merck, 60–230 mesh) or aluminum oxide (Merck, 70–230 mesh). All solvents were of anhydrous quality purchased from Aldrich Chemical Co. and used as received.

Optical rotations were measured at ambient temperature for solution in CHCl₃ with a Perkin–Elmer automatic polarimeter, Model 341. Melting points were measured on a Kofler hot stage. All reactions were monitored by thin-layer chromatography (TLC) on silica gel 60 coated glass slides. Spots were visualized by charring with 5% H₂SO₄ in ethanol, 1% ninhydrine in ethanol, or UV light, as required. Column chromatography was performed by elution from prepacked (Biotage, Inc.) columns of silica gel with a Isolera Flash Chromatograph (Biotage), the latter being connected to an external Evaporative Light Scattering Detector, Model 380-LC (Varian, Inc.). Nuclear Magnetic Resonance (NMR) spectra were measured at 600 MHz for ¹H, and 150 MHz for ¹³C with Bruker Avance spectrometers. Solvent peaks were used as internal references relative to TMS for ¹H and ¹³C chemical shifts (ppm). Assignments of NMR signals were made by homonuclear and heteronuclear two-dimensional correlation spectroscopy, run with software supplied with the spectrometers. Liquid Chromatography–Electron Spray-Ionization Mass Spectrometry (ESI-MS) was performed with a Hewlett–Packard 1100 MSD spectrometer. Solutions in organic solvents were dried with anhydrous Na₂SO₄, and concentrated at 40°C/2 kPa.