Acid Hydrolysis. The EtOAc extract, 487 mg, was heated under
reflux in 50 mL of 2 N HCl at 80 °C for 6 h. After removing HCl by
evaporation under vacuum, the mixture was diluted with H2O and
EtOAc (3 × 50 mL). The aqueous layer was neutralized with 0.1 M
NaOH.