Phosphinic, phosphonic and seleninic acid bioisosteres of isonipecotic acid as novel and selective GABAC receptor antagonists

A number of amino acids bioisosterically derived from the specific GABA(A) agonist, isonipecotic acid, were electrophysiologically characterized as antagonists at GABA(C) rho(1) receptors expressed in Xenopus oocytes. The phosphinic acid analogue of isonipecotic acid, piperidin-4-ylphosphinic acid (2), was comparable with the standard GABA(C) antagonist, (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA), in terms of potency and GABAC versus GABAA receptor selectivity. Whereas the phosphonic acid analogue, piperidin-4-ylphosphonic acid (4), was at least an order of magnitude weaker than piperidin-4-ylphosphinic acid as a GABAC antagonist, the seleninic acid analogue, piperidin-4-ylseleninic acid (SEPI, 6), was the most potent and selective GABAC antagonist within the group of isonipecotic acid derived amino acids studied. (C) 2003 Elsevier Science Ltd. All rights reserved.