Melting points were determined on a Kofler hot-stage
apparatus and are uncorr. Optical rotations were mea-sured in MeOH at 28 C on a Perkin-Elmer 241 polarimeter.
UV absorptions were measured in MeOH on a
Shimadzu UV-240 spectrophotometer and IR spectra
were recorded in KBr discs on a Perkin-Elmer 283
double beam spectrophotometer. 1H and 13C NMR
spectra were recorded on Bruker Avance 400 and AC
300 spectrometers using DMSO-d6 and CDCl3 with
TMS as internal standard. 1H–1H COSY, HSQC,
HMBC and NOESY (500 ms mixing time) were
obtained using the standard pulse sequences. ESITOFMS
and ESI-MS/MS were recorded in positive
mode on a API Q-STAR PULSA of Applied Bio-system.
CC was carried out on silica gel (Acme) finer than
200 mesh (0.08 mm).