[{"from": "human", "value": "Create a molecule with the structure as the one described. The molecule is a 2-oxo monocarboxylic acid anion. It is functionally related to a pent-4-enoate. It is a conjugate base of a 2-oxopent-4-enoic acid. It is a tautomer of a 2-hydroxypenta-2,4-dienoate."}, {"from": "gpt", "value": "[C][=C][C][C][=Branch1][C][=O][C][=Branch1][C][=O][O-1]"}]