title: Resolution, configurational assignment, and enantiopharmacology at glutamate receptors of 2-amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionic acid (ACPA) and demethyl-ACPA.
abstract: We have previously described (RS)-2-amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionic acid (ACPA) as a potent agonist at the (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptor subtype of (S)-glutamic acid (Glu) receptors. We now report the chromatographic resolution of ACPA and (RS)-2-amino-3-(3-carboxy-4-isoxazolyl)propionic acid (demethyl-ACPA) using a Sumichiral OA-5000 column. The configuration of the enantiomers of both compounds have been assigned based on X-ray crystallographic analyses, supported by circular dichroism spectra and elution orders on chiral HPLC columns. Furthermore, the enantiopharmacology of ACPA and demethyl-ACPA was investigated using radioligand binding and cortical wedge electrophysiological assay systems and cloned metabotropic Glu receptors. (S)-ACPA showed high affinity in AMPA binding (IC(50) = 0.025 microM), low affinity in kainic acid binding (IC(50) = 3.6 microM), and potent AMPA receptor agonist activity on cortical neurons (EC(50) = 0.25 microM), whereas (R)-ACPA was essentially inactive. Like (S)-ACPA, (S)-demethyl-ACPA displayed high AMPA receptor affinity (IC(50) = 0.039 microM), but was found to be a relatively weak AMPA receptor agonist (EC(50) = 12 microM). The stereoselectivity observed for demethyl-ACPA was high when based on AMPA receptor affinity (eudismic ratio = 250), but low when based on electrophysiological activity (eudismic ratio = 10). (R)-Demethyl-ACPA also possessed a weak NMDA receptor antagonist activity (IC(50) = 220 microM). Among the enantiomers tested, only (S)-demethyl-ACPA showed activity at metabotropic receptors, being a weak antagonist at the mGlu(2) receptor subtype (K(B) = 148 microM).
authors.affiliation: NeuroScience PharmaBiotec Research Center, Department of Medicinal Chemistry, The Royal Danish School of Pharmacy, Copenhagen, Denmark.
authors.forename: T N
authors.initials: TN
authors.lastname: Johansen
authors.forename: T B
authors.initials: TB
authors.lastname: Stensbøl
authors.forename: B
authors.initials: B
authors.lastname: Nielsen
authors.forename: S B
authors.initials: SB
authors.lastname: Vogensen
authors.forename: K
authors.initials: K
authors.lastname: Frydenvang
authors.forename: F A
authors.initials: FA
authors.lastname: Sløk
authors.forename: H
authors.initials: H
authors.lastname: Bräüner-Osborne
authors.forename: U
authors.initials: U
authors.lastname: Madsen
authors.forename: P
authors.initials: P
authors.lastname: Krogsgaard-Larsen
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D006224:Cricetinae; D018360:Crystallography, X-Ray; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000378:metabolism*; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D007555:Isoxazoles / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D051381:Rats; D017470:Receptors, Glutamate / Q000737:chemistry*; D015290:Second Messenger Systems / Q000502:physiology; D013237:Stereoisomerism
chemical_list: C440209:2-amino-3-(3-carboxy-4-isoxazolyl)propionic acid; C120781:2-amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionic acid; D018690:Excitatory Amino Acid Agonists; D007202:Indicators and Reagents; D007555:Isoxazoles; D017470:Receptors, Glutamate; D000409:Alanine