The present invention is related to a compound of formula (I)wherein R1 is selected from the group consisting of hydrogen, methyl and cyclopropylmethyl； AA-COOH is an amino acid selected from the group consisting of 2-amino-2-adamantane carboxylic acid, cyclohexylglycine and 9-amino-bicyclo[3.3.1]nonane-9-carboxylic acid； R2 is selected from the group consisting of (C1-C6)alkyl, (C3-C8)cycloalkyl, (C3-C8)cycloalkylmethyl, halogen, nitro and trifluoromethyl； ALK is (C2-C5)alkylidene； R3, R4 and R5 are each and independently selected from the group consisting of hydrogen and (Ci-C4)alkyl under the proviso that one of R3, R4 and R5 is of the formula (II)wherein ALK' is (C2-C5)alkylidene； R6 is selected from the group consisting of hydrogen and (C1-C4)alkyl； and R7 is selected from the group consisting of H and an Effector moiety； or a pharmacologically acceptable salt, solvate or hydrate thereof.
