General Experimental Procedures. The optical rotations
were obtained on a Perkin-Elmer 241 polarimeter, 1 dm cell.
IR spectra were recorded with a Perkin-Elmer 1600 spectrophotometer.
1D and 2D NMR spectra were recorded using
Bruker AMX-500 and WP-200 SY spectrometers; δ values in
parts per million relative to solvent (CDCl3) signal. DEPT, 1H- 1H COSY, HMQC, HMBC (J ) 8 Hz), and ROESY (spin lock
500 ms) experiments were carried out with the pulse sequences
given by Bruker. Mass spectra were measured with a Micromass
Autospec instrument. Alumina Merck Art. 1077 and 1101
were used for column chromatography and preparative TLC,
respectively. Zones on TLC plates were visualized with Dragendorff’s
reagent.