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 tert-butyl (3R,4R)-3-(2-amino-6-oxo-1H-purin-9-yl)-4-hydroxy-4-methyl-1-oxa-9-azaspiro[5.5]undecane-9-carboxylate is given. What is its corresponding molecular formula?
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C20H30N6O5
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