[{"from": "human", "value": "Create a molecule that satisfies the conditions outlined in the description. The molecule is one of the early purine analogs showing antineoplastic activity. It functions as an antimetabolite and is easily incorporated into ribonucleic acids."}, {"from": "gpt", "value": "[C][=N][N][N][=C][Ring1][Branch1][N][=C][Branch1][=Branch1][N][C][Ring1][=Branch2][=O][N]"}]