Vnmrs 600 instrument

¹H and ¹³C NMR spectra were recorded in deuterochloroform at ambient temperature using a Varian VNMRS-600 instrument. Chemical shift values are quoted in parts per million and J values in Hertz. IR spectra were recorded on a Perkin-Elmer 1600 series FT-IR spectrometer. Mass spectra were obtained on a Finnigan MAT Model 8200 spectrometer. UV spectra were taken on a Shimadzu Model 160A UV-VIS spectrophotometer in the solvents indicated. Column flash chromatography was performed on silica gel Si 60 (230–400 mesh, Merck, Darmstadt, Germany). Reactions were monitored by thin-layer chromatography (TLC) performed using Merck Kieselgel 60 F₂₅₄ plates. The TLC plates were visualized with a combination of UV light and an aqueous solution of cerium (IV)/phosphomolybdenic acid at a high temperature. The analytical and preparative separations of HPLC were performed using a Knauer Model 64 instrument with Eurospher 100 C18 column (40 × 250 mm). All moisture-sensitive reactions were performed in flame-dried glassware under argon.

Unless specifically indicated, all other chemicals and reagents used in this study were purchased from commercial sources and used as received. If necessary, purification of products was performed using column chromatography on silica gel (Merck Kieselgel 60, 230–400 mesh) with mixtures of chloroform/methanol. Thin-layer chromatography (TLC) was performed on silica gel plates (Merck Kieselgel 60 F254).
¹H and ¹³C NMR spectra used in the characterization of products were recorded on Bruker 300 spectrometer (Bruker Corporation, Billerica, MA, USA) using a residual protonated solvent as internal standard. ¹H NMR DOSY experiments were conducted at 298 K on Varian VNMRS-600 instrument (Varian Inc., Palo Alto, CA, USA) with a residual solvent signal as an internal standard.
High-resolution mass spectra (HRMS) were measured on a LCT (TOF) Micromass unit (Waters Corporation, Milford, CT, USA) using electrospray ionization (ESI) technique.
High performance ion chromatography (HPIC) analyses were performed using a 930 Compact IC Flex apparatus (Metrohm AG, Herisau, Switzerland).