500 spectrometers

All reactions were carried out under an atmosphere of nitrogen in flame-dried glassware with magnetic stirring unless otherwise indicated. Commercially obtained reagents were used as received. Solvents were dried by passage through an activated alumina column under argon. Liquids and solutions were transferred via syringe. All reactions were monitored by thin-layer chromatography with E. Merck silica gel 60 F254 pre-coated plates (0.25 mm). Structures of the target compounds in this work were assigned by use of NMR spectroscopy and MS spectrometry. The purities of all compounds were >95% as determined on Waters HPLC (Column: X Bridge C18, Eluents: 0.1% NH₄HCO₃/H₂O and CH₃CN) with 2998PDA and 3100MS detectors, using ESI as ionization. Pre-HPLC is used to separate and refine high-purity target compounds. ¹H and ¹³C NMR spectra were recorded on Varian Inova-400 or 500 spectrometers. Data for ¹H NMR spectra are reported relative to CDCl₃ (7.26 ppm), CD₃OD (3.31 ppm), or DMSO-d6 (2.50 ppm) as an internal standard and are reported as follows: chemical shift (δ ppm), multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, sept = septet, m = multiplet, br = broad), coupling constant J (Hz), and integration.

Reactions were routinely monitored by thin-layer chromatography (TLC) on silica gel (precoated Macherey-Nagel, 60FUV254). Flash chromatography was performed using Macherey-Nagel, silica 60, 230–400 mesh silica gel. Light petroleum ether refers to the fractions boiling at 40–60 °C. Melting points were determined on a Buchi-Tottoli instrument and are uncorrected. ¹H NMR were determined in CDCl₃, DMSO-d₆ or CD₃OD solutions with a Varian Gemini 200, a Bruker 400 or a Varian 500 spectrometers. Peaks positions are given in parts per million (δ) downfield relative to the central peak of the solvents, and J values are given in Hz. The following abbreviations were used: s, singlet; bs, broad singlet; d, doublet; dd, double doublet; bd, broad doublet; t, triplet; m, multiplet. Electrospray mass spectra were recorded on a ESI Bruker 4000 Esquire spectrometer and compounds were dissolved in methanol; accurate mass spectra were recorded on a micrOTOF-Q-Bruker and compounds were dissolved in methanol. Absorption experiments were performed on a Varian Cary 5000 spectrophotometer. Fluorescence measurements were recorded on Varian Cary Eclipse fluorescence spectrophotometer, with excitation filter at 361 nm, emission filter at 390–600 nm (all experiments were performed using a λ_ex of 488 nm). Oct-7-ynoic acid was synthesized as reported in the literature.