 oil, which was fractionated by gravity column chromatography on silica gel (*n*-hexane−EtOAc, 0:0 to 0:0, as solvent gradient system). Fractions eluted with *n*-hexane−EtOAc (0:0) were further purified by HPLC (*n*-hexane−EtOAc, 00:00) to yield 