5-Oxo-L-proline 1-methylethyl ester, isopropyl (+)-L-pyroglutamate, L-Pyroglutamic acid isopropyl ester, isopropyl 5-oxo-L-prolinate, pyroglutamic acid iso-propyl ester, (S)-iso-Propyl pyroglutamate, isopropyl pyrrolidin-5-one-2(S)-carboxylate, isopropyl (S)-(-)-2-pyrrolidone-5-carboxylate