Asymmetric Synthesis of Lycoperdic Acid

Abstract

Lycoperdic acid [(2S, 5'S)-2-amino-3-(5'-carboxy-2'-oxo-5'-tetrahydrofuranyl)propanoic acid], isolated from the mushroom Lycoperdon perlatum, was synthesized from trans-4-hydroxy-L-proline by a six-step route involving samarium diiodide (SmI₂)-mediated formation of the spiro-γ-lactone and ruthenium tetroxide (RuO₄) oxidation of the L-proline ring system to the L-pyroglutamic acid moiety. Lycoperdic acid (1) was found to undergo hydrolysis of the γ-lactone ring in 1 N hydrochloric acid at 23°C, giving an equilibrated mixture of 1 and the corresponding hydroxy acid.