title: Synthesis and dopamine receptor affinities of N-alkyl-11-hydroxy-2-methoxynoraporphines: N-alkyl substituents determine D1 versus D2 receptor selectivity.
abstract: We developed a procedure to synthesize a series of N-alkyl-2-methoxy-11-hydroxynoraporphines from thebaine and evaluated their binding affinities at dopamine D1 and D2 receptors in rat forebrain tissue. At D2 receptors, the most potent 10,11-catechol-aporphine was (R)-(-)-2-methoxy-N-n-propylnorapomorphine (D2, Ki = 1.3 nM; D1, Ki = 6450 nM), and the most selective and potent 11-monohydroxy aporphine was (R)-(-)-2-methoxy-11-hydroxy-N-n-propylnoraporphine (D2, Ki = 44 nM; D1, Ki = 1690 nM). In contrast, the N-methyl congeners (R)-(-)-2-methoxy-11-hydroxy-N-methyl-aporphine (D1 vs D2, Ki = 46 vs 235 nM) showed higher D1 than D2 affinity, indicating that N-alkyl substituents have major effects on D2 affinity and D2/D1 selectivity in such 2-methoxy-11-monohydroxy-substituted aporphines.
authors.affiliation: Alcohol & Drug Abuse Research Center, McLean Hospital, Harvard Medical School, 115 Mill Street, Belmont, Massachusetts 02478-9106, USA.
authors.forename: Yu-Gui
authors.initials: YG
authors.lastname: Si
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Gardner
authors.forename: Frank I
authors.initials: FI
authors.lastname: Tarazi
authors.forename: Ross J
authors.initials: RJ
authors.lastname: Baldessarini
authors.forename: John L
authors.initials: JL
authors.lastname: Neumeyer
mesh_terms: D000818:Animals; D001060:Aporphines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001667:Binding, Competitive; D003342:Corpus Striatum / Q000378:metabolism; D066298:In Vitro Techniques; D011869:Radioligand Assay; D051381:Rats; D017447:Receptors, Dopamine D1 / Q000819:agonists*; D017448:Receptors, Dopamine D2 / Q000819:agonists*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D001060:Aporphines; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2