Patent ID: 6875886

Claim:
A compound represented in the formula (II): wherein: R represents a chelate ligand, a fluorescence tag, or a cytotoxic moiety; R3 represents an alkyl, an alkenyl, a cycloalkyl, a cycloalkenyl, an aryl, —(CH 2 ) m -aryl, -alkyl-CO 2 R4, -alkenyl-CO 2 R4, -cycloalkyl-CO 2 R4, -cycloalkenyl-CO 2 R4 or -aryl-CO 2 R4; R2 and R4, independently for each occurrence, represent hydrogen, a lower alkyl, or a pharmaceutically acceptable salt; m is 1, 2, 3 or 4; and, n is 0, 1, 2 or 3.