You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[2-acetyloxy-3,5-dihydroxy-6-(4,5,9-trihydroxy-10-oxoanthracen-9-yl)oxan-4-yl] 3-methylbut-2-enoate is the IUPAC name of a molecule. Please give its molecular formula.
user
C26H26O11
assistant