You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [(5S)-5-[(2S,4S,5R)-2-[2-(3,4-dihydroxyphenyl)-5-hydroxy-4-oxochromen-7-yl]oxy-4,5-dihydroxyoxan-3-yl]oxy-4-hydroxy-3-(hydroxymethyl)oxolan-3-yl] acetate by IUPAC nomenclature, provide its molecular formula.
user
C27H28O15
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