Dibromotyrosine derivatives from the ethanol extract of the marine sponge Aplysina sp.: structures, transformations, and origin

Twenty nine 3,5-dibromotyrosine derivatives were isolated from the ethanol extract of the marine sponge Aplysina sp. (South China Sea) including the earlier unknown compounds, in particular, p-hydroxycyclohexadienone and p-hydroxycyclohexenone ketals. The isolated enones, dienones, and ketals can be transformation products of aeroplysinin-1 in the course of its reactions with water and alcohols.