- Dopamine Agonists Related to 3-Allyl-6-chloro-2,3,4,5-tetrahydro-1-(4-hydroxyphenyl)-1H-3-benzazepine-7,8-diol. 6-Position Modifications
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The N-allyl derivative (SK and F 85174) of 6-chloro-2,3,4,5-tetrahydro-1-(4-hydroxyphenyl)-1H-3-benzazepine-7,8-diol (SK and F 82526) retains the DA-1 agonist potency of the latter compound but unlike the parent also shows substantial DA-2 agonist activity.In a previous study of N-substituted benzazepines these combined agonist effects were shown to be uniquely associated with the N-allyl group.A continuation of this research has examined dependency of combined DA-2/DA-1 agonist activities on 6=position modification with the specific objective of developing an agonist with maximum effectiveness and potency at the DA-2 receptor subtype.DA-2 agonist activity was measured in a rabbit ear artery assay, and DA-1 agonist activity was determined in an adenylate cyclase assay.Replacing chloro with bromo retains the activity pattern and the potency of the chloro compound: replacement with a hydrogen causes a decrease of both DA-1 and DA-2 receptor activating potency.Introduction of a 6-methyl group causes loss of DA-2 agonist activity and reduction in DA-1 agonist potency.Substitution with a 6-fluoro provides the best balance of DA-2 and DA-1 agonist activities; this compound was moderately in both assays.
- Ross, Stephen T.,Franz, Robert G.,Gallagher, Gregory,Brenner, Martin,Wilson, James W.,et al.
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- Synthesis and Dopaminergic Activity of Some Halogenated Mono- and Dihydroxylated 2-Aminotetralins
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In a series of 7,8-dihydroxy-1-phenyltetrahydro-3-benzazepine dopamine receptor agonists introduction of a chloro or fluoro substituent into the 6-position increases dopaminergic potency.Also, in this series replacement of the 7-hydroxyl group with a halogen results in inversion of activity from dopamine receptor agonist to antagonist.The present study was aimed at exploring the possibility that the structure-activity observations in the 3-benzazepine series of dopaminergic agents might be extrapolated to another class of dopamine receptor agonists, the 2-aminotetralins.Thus, a series of chloro- and fluoro-substituted mono- and dihydroxylated 2-aminotetralins was prepared and evaluated for dopaminergic properties in D-1 and D-2 receptor-related tests.Introduction of a chloro substituent into the 8-position of the prototype of this series, i.e. 2-amino-6,7-dihydroxytetralin (ADTN), resulted in a compound with a high degree of selectivity for the D-1 subpopulation of dopamine receptors; it was equally or more potent than ADTN in the D-1 receptor-related tests with greatly decreased effectiveness in the tests involving D-2 receptors.A similar effect was observed with 8-fluoro-ADTN; however, the N-(4-hydroxyphenethyl)-N-propyl derivative 4g of the 8-chloro-substituted ADTN showed markered D-2 binding affinity.Conversely, introduction of a chloro substituent into the 5-position of ADTN markedly decreased D-1 receptor affinity and efficacy.This effect was not seen with the related 5-fluoro derivative, suggesting D-1 receptors are more sensitive to bulk in the 5-position of ADTN than are the D-2 receptors.Replacement of either the 6- or 7-hydroxyl groups of ADTN with a chloro or fluoro substituent, in contrast, did not parallel the response seen in the benzazepine series (i.e., the compounds uniformly demonstrated less receptor affinity and did not have dopamine receptor antagonist activity); however, the decrease in agonist potency was less marked in the case of 2-amino-6-fluoro-7-hydroxytetralins than in the chlorinated monohydroxyaminotetralins.Thus, a parallelism in structure-activity relationships in the benzazepine and aminotetralin series of dopamine receptor agonists was not observed.The differences may reflect altered modes of receptor binding in the two series.
- Weinstock, Joseph,Gaitanopoulos, Dimitri E.,Oh, Hye-Ja,Pfeiffer, Francis R.,Karash, Carole B.,et al.
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p. 1615 - 1627
(2007/10/02)
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