You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-7-[(2S,3S,4S,5R,6S)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]anthracene-2-carboxylic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C22H20O13
assistant