Compounds of the formula:Wherein R is selected from the group consisting of H, NH2, and NHBoc and R′ is selected from the group consisting of H, CH2Ph and tBu, optionally de-protected. Such compounds may be conjugated with a suitable molecule able to interact with physiological systems and their chelates with bi-trivalent ions of the metal elements having atomic number ranging between 20 and 31, 39, 42, 43, 44, 49, and between 57 and 83, and radioisotopes chosen among 203Pb, 67Ga, 68Ga, 72As, 111In, 113In, 90Y, 97Ru, 62Cu, 64Cu, 52Fe, 52mMn, 140La, 175Yb, 153Sm, 166Ho, 149Pm, 177Lu, 142Pr, 159Gd, 212Bi, 47Sc, 149Pm, 67Cu, 111Ag, 199Au, 161Tb, 51Cr, 167Tm, 141Ce, 168Yb, 88Y, 165Dy, 166Dy, 97Ru, 103Ru, 186Re, 188Re, 99mTc, 211Bi, 212Bi, 213Bi, 214Bi, 105Rh, 109Pd, 117mSn, 177Sn and 199Au, as well as the salts thereof with physiologically compatible bases or acids.
