Evaluation of 99mTc-labeled tropanes with alkyl substituents on the 3β-phenyl ring as potential dopamine transporter tracers

Technetium(V)-oxo-3β-(4-chlorophenyl)-8-methyl-8-azabicyclo[3.2.1]oct-2-yl[N-(2-mercaptoethyl), N-(N′-(2-mercaptoethyl)-2-aminoethyl)]-aminomethyl (99mTc-TRODAT-1) and three derivatives with one or two substituents on the 3β-phenyl ring (4-methylphenyl, 4-ethylphenyl and 2,4-dimethylphenyl) were prepared and evaluated as potential imaging agents for the central nervous dopamine transporter (DAT). Labeling of the ligands with 99mTc yielded for each of them a mixture of t