Substituted cyclopentane compounds for use as chelating agents

Substituted cyclopentane compounds of the formula ##STR6## wherein X.sup.1, X.sup.2, X.sup.3 and X.sup.4 may be the same or different and each is selected from the group consisting of --CONRR.sup.1, --CH.sub.2 NHCOR, --CH.sub.2 OCOR, --CH.sub.2 OR.sup.1, --CH.sub.2 SR.sup.1, --CH.sub.2 SOR, --CH.sub.2 SO.sub.2 R or --CH.sub.2 SO.sub.2 NRR.sup.1,

• R may be the same or different and each is a C1-C12 hydrocarbon which is optionally substituted with a ligand donor group or a group which permits attachment to a biologically active molecule or insoluble support,
• R.sup.1 is H or R,
• Z is hydrogen or C1-C20 hydrocarbon which is optionally substituted with a group which permits attachment to a biologically active molecule or insoluble support,
• provided that when each of X.sup.1, X.sup.2, X.sup.3 and X.sup.4 is CH.sub.2 OR.sup.1, then R.sup.1 includes a ligand donor group,
• provided that, when each of X.sup.1, X.sup.2, X.sup.3 and X.sup.4 is --CONRR.sup.1, then R and R.sup.1 are not both C.sub.2-6 mono- or di-hydroxyalkyl and Z is not H, and
• provided that at least one of R, R.sup.1 and Z contain a ligand donor group or a group which permits attachment to a biologically active molecule or insoluble support.