Solutions of 1-5
(6 mg each) in 2 N HCl were heated (90 °C) for 2 h, after
removing HCl by evaporation in vacuum, the mixtures were
diluted with H2O and extracted with EtOAc. The EtOAc layer
in each case was evaporated to dryness, and the residue was
recrystallized in MeOH to afford trans-resveratrol, which was
identified by comparison with an authentic sample (co-TLC,
IR, and NMR7). The same treatment of compounds 6-10 (5
mg each) afforded cis-resveratrol, and its IR and NMR data
was consistent with that in the literature.7 A sample of each
aqueous layer (1-10) gave a positive sulfate test with BaCl2.