Abstract: A compound represented by formula (I): ##STR1## wherein R.sup.1 represents --CO--Z.sup.1 --N(Z.sup.11)--CO--Z.sup.2 --H or --CO--Z.sup.3 --H, wherein Z.sup.1, Z.sup.2, and Z.sup.3 each represent an alkylene group having from 1 to 20 carbon atoms, a phenylene group, or a combination thereof, and Z.sup.11 represents a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms which may be substituted with a phenyl group, a phenyl group which may be substituted with an alkyl group having from 1 to 20 carbon atoms, or an alkylene group having from 1 to 20 carbon atoms which may contain therein a phenylene group; R.sup.2 represents --CO--Z.sup.4 --N(Z.sup.12)--CO--Z.sup.5 --H, --CO--Z.sup.6 --H or a hydrogen atom, wherein Z.sup.4, Z.sup.5, and Z.sup.6 each have the same meaning as Z.sup.1, and Z.sup.12 has the same meaning as Z.sup.11 ; Q.sup.1 and Q.sup.2 each represent a carboxyl group or a phosphonoxy group; Q.sup.