[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule is a purine base that is a constituent of nucleotides occurring in nucleic acids."}, {"from": "gpt", "value": "[C][=N][C][=C][Branch1][Ring2][N][Ring1][Branch1][C][=Branch1][C][=O][N][C][=Branch1][Ring2][=N][Ring1][Branch2][N]"}]