A compound of the formula: ##STR1## wherein R.sup.1 is a hydrogen atom or a methyl group, R.sup.2 is a hydrogen atom or a negative charge, R.sup.3 is a hydrogen atom, a halogen atom, a hydroxyl group, a lower alkoxy group, a lower alkanoyloxy group, an amino group, an N-lower alkylamino group, an N,N-di-lower alkylamino group, a lower alkanoylamino group, an aroylamino group, a (lower alkylsulfonyl)amino group, a sulfamoylamino group, a cyano group, a nitro group, a group of --COOR.sup.4 (wherein R.sup.4 is a hydrogen atom or a lower alkyl group) or a group of --CON(R.sup.5)R.sup.6 (wherein each of R.sup.5 and R.sup.6 which may be the same or different, is a hydrogen atom or a lower alkyl group, or R.sup.5 and R.sup.6 form together with the adjacent nitrogen atom a heterocyclic group selected from the group consisting of an aziridinyl group, an azetidinyl group, a pyrrolidinyl group, a piperidyl group, a piperazinyl group, a 4-lower alkyl piperazinyl group and a morpholino group), A is a linear or branched lower alkylene group, X is a group of --N(R.sup.7)R.sup.8 (wherein each of R.sup.7 and R.sup.8 which may be the same or different, is a hydrogen atom or a lower alkyl group) or a group of --N.sup.+ (R.sup.9)(R.sup.10)R.sup.11 (wherein each of R.sup.9, R.sup.10 and R.sup.11 which may be the same or different, is a lower alkyl group), provided that when A is a linear lower alkylene group, R.sup.3 is other than a hydrogen atom; or a pharmaceutically acceptable salt or ester thereof.