You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule (4aR,5S,6R,8aR)-5-[2-[(2S)-2-methoxy-5-oxo-2H-furan-4-yl]ethyl]-5,6,8a-trimethyl-4a,6,7,8-tetrahydronaphthalene-1-carboxylic acid into molecular formula.
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C21H28O5
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