Resolution, absolute stereochemistry, and enantiopharmacology of the GluR1–4 and GluR5 antagonist 2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid

✍ Scribed by Eva H. Møller; Jan Egebjerg; Lotte Brehm; Tine B. Stensbøl; Tommy N. Johansen; Ulf Madsen; Povl Krogsgaard-Larsen

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 702 KB
• Volume: 11
• Category: Article
• ISSN: 0899-0042
• DOI: 10.1002/(sici)1520-636x(1999)11:10<752::aid-chir3>3.0.co;2-t

✦ Synopsis

The phosphono amino acid, (RS)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid (ATPO), is a structural hybrid between the NMDA antagonist (RS)-2-amino-7-phosphonoheptanoic acid (AP7) and the AMPA and GluR5 agonist, (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA). ATPO has been resolved into (S)-ATPO and (R)-ATPO using chiral HPLC, and the absolute stereochemistry of the two enantiomers was established by an X-ray crystallographic analysis of (R)-ATPO. (S)-ATPO and (R)-ATPO were characterized pharmacologically using rat brain membrane binding and electrophysiologically using the cortical wedge preparation as well as homo-or heteromeric GluR1-4, GluR5-6, and KA2 receptors expressed in Xenopus oocytes. (R)-ATPO was essentially inactive as an agonist or antagonist in all test systems. (S)-ATPO was an inhibitor of the binding of [ 3 H]AMPA (IC 50 = 16 ± 1 µM) and of [ 3 H]-6-cyano-7-nitroquinoxaline-2,3-dione ([ 3 H]CNQX) (IC 50 = 1.8 ± 0.2 µM), but was inactive in the [ 3 H]kainic acid and the [ 3 H]-(RS)-3-(2carboxypiperazin-4-yl)propyl-1-phosphonic acid ([ 3 H]CPP) binding assays. (S)-ATPO did not show detectable agonist effects at any of the receptors under study, but antagonized AMPA-induced depolarization in the cortical wedge preparation (IC 50 = 15 ± 1 µM). (S)-ATPO also blocked kainic acid agonist effects at GluR1 (K i = 2.0 µM), GluR1+2 (K i = 3.6 µM), GluR3 (K i = 3.6 µM), GluR4 (K i = 6.7 µM), and GluR5 (K i = 23 µM), but was inactive at GluR6 and GluR6+KA2. Thus, although ATPO is a structural analog of AP7 neither (S)-ATPO nor (R)-ATPO are recognized by NMDA receptor sites. Chirality 11: 752-759, 1999.