preferred_name: (2R,3S)-3-isopropylmalate => (2S)-2-isopropylmalate
preferred_name_lc: (2r,3s)-3-isopropylmalate => (2s)-2-isopropylmalate
label: (2R,3S)-3-isopropylmalate => (2S)-2-isopropylmalate
label_lc: (2r,3s)-3-isopropylmalate => (2s)-2-isopropylmalate