You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(2-chloro-4-methylphenyl)-1-[5-chloro-2-[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxyphenyl]ethanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H22Cl2O7
assistant