[{"from": "human", "value": "Create a molecule with the structure as the one described. The molecule is a butan-4-olide that is tetrahydrofuran substituted by an oxo group at position 2. It has a role as a neurotoxin and a metabolite."}, {"from": "gpt", "value": "[C][C][C][=Branch1][C][=O][O][C][Ring1][=Branch1]"}]