Derivates of 6-methyl-8alpha-amino-ergoline: Sythesis and affinity to the dopamine D₂ receptor

Organic derivatives (2) of 6-methyl-8alpha-amino-ergoline 1 and derived complexes of rhenium (3,5) and technetium (4) have been prepared and evaluated with regard to their affinity to the dopamine D₂ receptor. The molecular structure of the rhenium complex 3 was determined. The affinity of the benzoyl derivative 2b is comparable with that of terguride (IC₅₀ values 2.7 for 2b vs. 4.8 nMol), while the affinities of the related Tc and Re complexes are in the range from 54 to 165 nMol.