title: Tetrazolyl isoxazole amino acids as ionotropic glutamate receptor antagonists: synthesis, modelling and molecular pharmacology.
abstract: Two 3-(5-tetrazolylmethoxy) analogues, 1a and 1b, of (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA), a selective AMPA receptor agonist, and (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA), a GluR5-preferring agonist, were synthesized. Compounds 1a and 1b were pharmacologically characterized in receptor binding assays, and electrophysiologically on homomeric AMPA receptors (GluR1-4), homomeric (GluR5 and GluR6) and heteromeric (GluR6/KA2) kainic acid receptors, using two-electrode voltage-clamped Xenopus laevis oocytes expressing these receptors. Both analogues proved to be antagonists at all AMPA receptor subtypes, showing potencies (Kb=38-161 microM) similar to that of the AMPA receptor antagonist (RS)-2-amino-3-[3-(carboxymethoxy)-5-methyl-4-isoxazolyl]propionic acid (AMOA) (Kb=43-76 microM). Furthermore, the AMOA analogue, 1a, blocked two kainic acid receptor subtypes (GluR5 and GluR6/KA2), showing sevenfold preference for GluR6/KA2 (Kb=19 microM). Unlike the iGluR antagonist (S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid [(S)-ATPO], the corresponding tetrazolyl analogue, 1b, lacks kainic acid receptor effects. On the basis of docking to a crystal structure of the isolated extracellular ligand-binding core of the AMPA receptor subunit GluR2 and a homology model of the kainic acid receptor subunit GluR5, we were able to rationalize the observed structure-activity relationships.
authors.affiliation: Department of Medicinal Chemistry, The Danish University of Pharmaceutical Sciences, 2 Universitetsparken, DK-2100 Copenhagen, Denmark. bfr@dfuni.dk
authors.forename: Bente
authors.initials: B
authors.lastname: Frølund
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Greenwood
authors.forename: Mai M
authors.initials: MM
authors.lastname: Holm
authors.forename: Jan
authors.initials: J
authors.lastname: Egebjerg
authors.forename: Ulf
authors.initials: U
authors.lastname: Madsen
authors.forename: Birgitte
authors.initials: B
authors.lastname: Nielsen
authors.forename: Hans
authors.initials: H
authors.lastname: Bräuner-Osborne
authors.forename: Tine B
authors.initials: TB
authors.lastname: Stensbøl
authors.forename: Povl
authors.initials: P
authors.lastname: Krogsgaard-Larsen
mesh_terms: D000818:Animals; D002460:Cell Line; D003198:Computer Simulation; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D007555:Isoxazoles / Q000737:chemistry; D008958:Models, Molecular; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011422:Propionates / Q000737:chemistry; D051381:Rats; D017470:Receptors, Glutamate / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D007555:Isoxazoles; D011422:Propionates; D017470:Receptors, Glutamate; C081662:alpha-amino-3-hydroxy-5-tert-butyl-4-isoxazolepropionate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid