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system
Name the molecular formula for the molecule established as 1-[4-[(2R)-1-[(5S)-2,6-dioxa-9-azaspiro[4.5]decan-9-yl]-1-oxopropan-2-yl]phenyl]-2-methylpropan-1-one using the IUPAC nomenclature.
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C20H27NO4
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