The silver salt of desmotroposantonous acid (Ⅲ) when reacting with bromine in molar ratio forms principally the nuclear brominated compound (Ⅵ). The phenolic hydroxyl group of desmotroposantonin and desmotroposantonous acid as well as their brominated products may or may not be etherified with diazomethane as depending upon the kind of the group existing in the molecule.