General experimental Analytical TLC was performed on precoated (250 μm) silica gel 60 F-254 plates from Merck. All plates were visualized by UV irradiation, and/or staining with 5% H2SO4 in ethanol followed by heating. Flash chromatography grade silica gel 60 (230-400 mesh) was obtained from Merck. Mass analysis was performed on an Ettan MALDI-TOF Pro from Amersham Biosciences or LASER-TOF LT3 from Scientific Analytical Instruments with 3- hydroxypicolinic acid or 2,’ 4’, 6’-trihydroxyacetophenone as matrix. The NMR spectra were obtained at 1H (300 MHz), 13C (75 MHz) and 31P (121 MHz) on a Bruker instrument at 25 ºC. Chemical shifts are reported in ppm downfield from TMS as standard. HPLC was carried out using a Gilson instrument equipped with a UV detector and a Nucleosil C18 column (4.0 × 250 mm) or Phenomenex Clarity. Fluorescence spectra were recorded on a Varian Cary Eclipse instrument. All other chemical agents were purchased from Aldrich Chemical Company unless otherwise noted.