[{"from": "human", "value": "Synthesize a molecule that matches the given characteristics. The molecule is a purinemonocarboxylic acid. It is functionally related to a xanthine. It is a conjugate acid of a xanthine-8-carboxylate."}, {"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]"}]