You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name 2-[2-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-2-oxoethyl]-4-nitroisoindole-1,3-dione into its molecular formula.
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C21H19N3O7
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