You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named [(2R,5R,7S,8S,10R,15R,17S)-7,15-dihydroxy-8,12,17-trimethyl-9-oxo-4-oxapentacyclo[9.5.1.01,8.02,5.015,17]heptadec-11-en-10-yl] acetate is given. What is its corresponding molecular formula?
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C21H28O6
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