(Triphenylphosphoranylidene)succinic anhydride, which is prepared from triphenylphosphine and maleic anhydride and is itself not reactive towards aryl aldehydes, is ring-opened with methanol to methyl (triphenylphosphoranylidene)succinate. In one pot, the newly formed phosphorane is reacted with aryl aldehydes to methyl aryl itaconates, which are subsequently hydrolyzed with aqueous sodium hydroxide to aryl itaconic acids. The biological activity of 12 aryl itaconic acids thus prepared against four gram-positive and four gram-negative bacterial strains has been studied.