[{"from": "human", "value": "Create a molecule that satisfies the conditions outlined in the description. The molecule is the conjugate base of 4-carboxymethyl-4-methylbut-2-en-1,4-olide; major species at pH 7.3. It is a conjugate base of a 4-carboxymethyl-4-methylbut-2-en-1,4-olide."}, {"from": "gpt", "value": "[C][C][Branch1][#Branch2][C][=C][C][=Branch1][C][=O][O][Ring1][=Branch1][C][C][=Branch1][C][=O][O-1]"}]