[{"from": "human", "value": "Synthesize a molecule that matches the given characteristics. The molecule is the conjugate base of propionic acid; a key precursor in lipid biosynthesis. It has a role as a human metabolite. It is a conjugate base of a propionic acid."}, {"from": "gpt", "value": "[C][C][C][=Branch1][C][=O][O-1]"}]