A method for producing a compound represented by the formula: ##STR1## wherein the ring A is a benzene ring which may be substituted in addition to the R' group; R.sup.1 is hydrogen or an optionally substituted hydrocarbon residue; X is a direct bond or a spacer having an atomic length or two or less between the phenylene group and the phenyl group; Y is --O--, --S(O)m-- or --N(R.sup.4)-- wherein m is an integer of 0, 1 or 2 and R.sup.4 is hydrogen or an optionally substituted alkyl group; R' is carboxyl, an ester thereof, an amide thereof or a group capable of forming an anion or a group convertible thereinto; n is an integer of 1 or 2; or a salt thereof, which comprises deprotecting a compound represented by the formula: ##STR2## wherein R is triphenylmethyl, 2-tetrahydropyranyl, methoxymethyl or ethoxy methyl, the other symbols as defined above; or a salt thereof.