Abstract: Biodegradable and little skin-roughening carboxylic acids being an excellent surfactant in a wide pH range and having the general formula (1): ##STR1## wherein R is a linear or branched alkyl or alkenyl group containing from 4 to 34 carbon atoms; one or both of X.sub.1 and X.sub.2 are --(CH.sub.2).sub.n --COOM, any other is a hydrogen atom; M is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium, a lower alkanol amine cation, a lower alkyl-amine cation or a basic amino acid cation; and n is 1 or 2; and simple methods of preparing the same.