You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 3-[2-[(2R,6R)-2,6-dimethylmorpholin-4-yl]-2-oxoethyl]-6-(4-methoxyphenyl)thieno[3,2-d]pyrimidin-4-one by IUPAC nomenclature, provide its molecular formula.
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C21H23N3O4S
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