You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 6-amino-5-[(2R)-2-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)propanoyl]-1,3-dimethylpyrimidine-2,4-dione by IUPAC nomenclature, provide its molecular formula.
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C20H26N4O5
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