[{"from": "human", "value": "Generate a molecule based on this description. The molecule is a branched-chain saturated fatty acid anion that is pentanoate with a methyl group substituent at position 4. It has a role as a metabolite. It is a branched-chain saturated fatty acid anion and a medium-chain fatty acid anion. It is a conjugate base of an isocaproic acid."}, {"from": "gpt", "value": "[C][C][Branch1][C][C][C][C][C][=Branch1][C][=O][O-1]"}]