[{"from": "human", "value": "Based on the given information, design a molecule that meets the desired specifications. The molecule is a purinecarboxylate. It is functionally related to a xanthine. It is a conjugate base of a xanthine-8-carboxylic acid."}, {"from": "gpt", "value": "[C][=C][Branch1][O][N][C][=Branch1][C][=O][N][C][Ring1][#Branch1][=O][N][=C][Branch1][Ring2][N][Ring1][O][C][=Branch1][C][=O][O-1]"}]