Psychotridine
Penipurdin A
L-Pyroglutamic acid
5-Oxo-L-proline, NSC 143034, (2S)-5-Oxopyrrolidine-2-carboxylic acid
D-Pyroglutamic acid
5-Oxo-D-proline, (2R)-5-Oxopyrrolidine-2-carboxylic acid
L-Pyrohomoglutamic acid
L-Pyro-α-aminoadipic acid, (2S)-6-Oxopiperidine-2-carboxylic acid
D-Pyrohomoglutamic acid
(2R)-6-Oxo-2-piperidinecarboxylic acid
L-Pyroaspartic acid
D-Pyroaspartic acid
Piliformic acid
(2E)-2-Hexylidene-3-methylbutanedioic acid