You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (2S,3S,4S,5R,6S)-6-[2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxochromen-8-yl]oxy-3,4,5-trihydroxyoxane-2-carboxylic acid .
user
C21H18O13
assistant