[{"from": "human", "value": "Generate a molecule based on this description. The molecule is 2-Methyl-3-oxopropanoate with S configuration at the chiral centre. It is a conjugate base of a (S)-methylmalonaldehydic acid. It is an enantiomer of a (R)-methylmalonate semialdehyde."}, {"from": "gpt", "value": "[C][C@@H1][Branch1][Ring1][C][=O][C][=Branch1][C][=O][O-1]"}]