A class of compounds formed by condensation of a phenolic carboxylic acid (such as gallic acid) with a similar compound, the reaction being between the carboxylic acid group on one molecule and a phenolic OH group on the other. Depsides are similar to esters, except that the OH group is linked directly to an aromatic ring. In such compounds, the –O–CO– group is called a depside linkage. Depsides are found in tannins and other natural products.