methyl 2-[(2R,5S)-2-tert-butyl-5-ethyl-4-oxo-1,3-dioxolan-5-yl]-4-oxo-4,6-dihydroindolizino[1,2-b]quinoline-3-carboxylate

乙基丙二酸二甲酯

dimethyl 2-ethyl-2-hydroxymalonate

2-(methoxycarbonyl)-2-(methoxymethoxy)butanoic acid