Syntheses and biological evaluation of 2- and 9-aminobenzonorbornenes as conformationally rigid analogs of amphetamines.
Isomers of the 2- and 9-aminobenzonorbornenes were prepared as rigid analogs of amphetamine and were employed to study the conformational requirements of indirectly acting sympathomimetic agents. Of this series of isomeric amines, the exo-2 and anti-9 isomers closely resemble the fully extended conformation of amphetamine. The other two amines, the endo-2 and syn-9 isomers, conformationally resemble the folded conformation of amphetamine. The isomers that resemble the extended conformation of amphetamine increased the spontaneous motor activity in mice while the isomers resembling the folded form either decreased or had no effect on motor activity. These compounds also were studied for their ability to accelerate the efflux of tritiated norepinephrine from vesicular and nonvesicular storage sites of isolated perfused rabbit atria; either alpha-methyl-p-tyrosine- or reserpine-pretreated rabbits were used. Amphetamine and the exo-2 and anti-9 isomers of aminobenzonorbornene could accelerate norepinephrine efflux from either compartment while the endo-2 and syn-9 isomers could accelerate the efflux from only the nonvesicular compartment at the concentrations studied. Fenfluramine and methylphenidate also were studied for their ability to accelerate efflux. Fenfluramine and methylphenidate resembled the aminobenzonorbornenes that correspond to the folded conformation of amphetamine in their ability to accelerate the efflux from nonvesicular storage. However, fenfluramine also resembled amphetamine and the aminobenzonorbornenes corresponding to the extended conformation of amphetamine in its ability to accelerate efflux from vesicular storage sites. The response to methylphenidate was similar to that of the aminobenzonorbornenes resembling the folded conformation of amphetamine.