[{"from": "human", "value": "Synthesize a molecule that matches the given characteristics. The molecule is a hydroxy monocarboxylic acid anion that is the conjugate base of 5-hydroxy-2,4-dioxopentanoic acid. It is a conjugate base of a 5-hydroxy-2,4-dioxopentanoic acid."}, {"from": "gpt", "value": "[C][Branch1][#Branch1][C][=Branch1][C][=O][C][O][C][=Branch1][C][=O][C][=Branch1][C][=O][O-1]"}]