Melting points were determined using a Gallenkamp melting
point apparatus and were uncorrected. Optical rotations were
obtained using a JASCO DIP-1000 digital polarimeter. UV spectra
were measured on an Agilent 8453 UV-visible spectrophotometer.
IR spectra were taken on a PerkineElmer Spectrum One spectrophotometer.
NMR spectra were recorded in CDCl3 and CD3OD on
a Varian Mercury Plus 400 spectrometer, using residual CHCl3 and
CH3OH as internal standards. HRMS spectra were obtained using
a Micromass LCT mass spectrometer, and the lock mass calibration
was applied for the determination of accurate masses. Column
chromatography and preparative TLC were carried out on silica gel
60 (230e400 mesh) and PF254, respectively.
3.2. Collection