Resolution, configurational assignment, and enantiopharmacology at glutamate receptors of 2-amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionic acid (ACPA) and demethyl-ACPA.
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).
Johansen
T N
TN
NeuroScience PharmaBiotec Research Center, Department of Medicinal Chemistry, The Royal Danish School of Pharmacy, Copenhagen, Denmark.
Stensbøl
T B
TB
Nielsen
B
B
Vogensen
S B
SB
Frydenvang
K
K
Sløk
F A
FA
Bräüner-Osborne
H
H
Madsen
U
U
Krogsgaard-Larsen
P
P
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
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