Some Synthetic Approaches to Glutamate AMPA Receptor Agonists Based on Isoxazolones

Abstract

Several approaches to the synthesis of derivatives of the antifungal antibiotic TAN-950A, which is also an agonist of glutamate at hippocampal neurons, are reported. Additions of isoxazolon-4-yl anions to methyleneoxazolidinones were not useful because addition occurred predominantly through N-2. Similarly addition of the isoxazolon-4-yl radicals to model Michael acceptors occurred predominantly through N-2. Racemic analogues of TAN-950A were prepared by reaction of isoxazolone Mannich bases with acetylaminomalonate or addition of β-ketoester anions to dehydroalanines. The best approach to enantiomerically pure analogues was by acylation of pyroglutamates, followed by reaction with hydroxylamine.