The invention relates to a method for producing compounds of formula (I) in which R1 represents an aromatic group containing 6 to 200 carbon atoms, R2 represents hydrogen, a linear or branched alkyl group containing 1 to 22 carbon atoms, a monounsaturated or polyunsaturated linear or branched alkenyl group containing 2 to 22 carbon atoms, or an aryl group containing 6 to 12 carbon atoms, X represents an alkylene group containing 2 to 4 carbon atoms, n represents a number between 0 and 100, and B represents a cation or hydrogen, and/or the corresponding protonated carboxylic acids, by oxidizing one or more compounds of formula (II) in which R1, R2, X, and n have the meaning indicated above, with oxygen or oxygen-containing gases in the presence of a gold-containing catalyst and at least one alkaline compound.