General Experimental Procedures. Melting points were
determined on a Thomas-Hoover “unimelt” apparatus. Optical
rotations were obtained on Perkin-Elmer 341 polarimeter. IR
spectra were recorded on a Nicolet 5000 infrared spectrometer.
1H and 13C NMR were measured on a Bruker Avance 500 MHz
NMR or 300 MHz instrument, and all 2D spectra NMR were
run on a Bruker 500 MHz NMR spectrometer. MS data were
recorded on a Micromass LC-MS system. Thin-layer chromatography
was performed on Whatman TLC plates (250 ím
thickness, K6F Si gel 60A), with compounds visualized by
spraying with 5% (v/v) H2SO4 in EtOH. Semipreparative HPLC
was carried out on a Varian Pro-Star system equipped with
UV-vis detector and a Dynamax C18 semipreparative column
(21.4 250 mm). Reversed-phase chromatography was carried
out on a Merck Lobar Lichroprep RP18 column. Si gel (Whatman,
230-400 mesh) and Sephadex LH-20 were used for
column chromatography.