[{"from": "human", "value": "Synthesize a molecule that matches the given characteristics. The molecule is dicarboxylate anion of 2-methylideneglutaric acid; major species at pH 7.3. It is a conjugate base of a 2-methylideneglutaric acid."}, {"from": "gpt", "value": "[C][=C][Branch1][Branch2][C][C][C][=Branch1][C][=O][O-1][C][=Branch1][C][=O][O-1]"}]