Dopamine Agonist Properties of N-Alkyl-4-(3,4-dihydroxyphenyl)-1,2,3,4-tetrahydroisoquinolines

Article abstract of DOI:10.1021/jm00140a021

A series of homologous N-alkyl-4-(3,4-dihydroxyphenyl)-1,2,3,4-tetrahydroisoquinolines was synthesized and examined for a dopamine-like ability to dilate the renal artery.The N-methyl derivative was equipotent to the 3',4'-dihydroxy derivative of the antidepressant agent nomifensine, indicating that the 8-amino group of the latter is not essential for dopamine-like activity.The N-ethyl homologue was reduced in potency when compared to the N-methyl, and the N-n-propyl, surprisingly, was essentially devoid of activity.This was unexpected in view of the fact that in all series of dopamine-like agents reported to date, N-alkylation, when one of the alkyls was an n-propyl group, either allowed retention or enhancement of potency.