SYNTHESIS AND AUTHENTICATION OF IODOAZIDOPHENPYRAMINE, A PHOTOAFFINITY REPORTER LIGAND PREVIOUSLY USED FOR HISTAMINE H-1-RECEPTOR LABELING

The synthesis is described of aminophenpyramine (7) (N-{5-[2-(4-aminop henyl)ethanamido]pentanyl}-N'- nzyl)-N-methyl-N'-(2-pyridinyl)-1,2-eth andiamine), its monoiodo- and diiodo-derivatives (8 and 9), and iodoaz idophenpyramine (1). The last compound is synthesised by two different routes to confirm the identity of the [I-125]iodinated ligand previou sly made only in solution and used for characterisation of the histami ne H-1-receptor protein. The procedures employ the novel intermediates 4-amino-3-iodo-phenylacetic acid (11) and 4-azido-3-iodo-phenylacetic acid (13). They have general applicability to the synthesis of non-ra dioactive iodinated photoaffinity receptor ligands which may be requir ed for chemical authentication of the corresponding radiolabelled comp ounds.