Bicyclic and tricyclic ergoline partial structures. Rigid 3-(2-aminoethyl)pyrroles and 3- and 4-(2-aminoethyl)pyrazoles as dopamine agonists

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Abstract
Based on comparisons with apomorphine, the rigid pyrroleethylamine moiety of the ergolines is the portion of the molecule responsible for dopamine agonist activity. In support of this hypothesis, bicyclic and tricyclic ergoline partial structures were synthesized. Some pyrazole isosters of these rigid pyrroleethylamines were made. All classes show dopaminergic activity in prolactin inhibition and in lesioned rat turning assays. The most potent drugs, the linear tricyclic pyrazoles trans-(.+-.)-4,4a,5,6,7,8,8a,9-octahydro-5-propyl-2H-pyrazolo[3,4-g]quinoline and (4a.beta.,7.beta.,8a.alpha.)-(.+-.)-4,4a,5,6,7,8,8a,9-octahydro-7-[(methylthio) methyl]-5-propyl-2H-pyrazolo[3,4-g]quinoline are comparable in potency with the highly active ergoline pergolide.