You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1S,2S,5S,6R,7S,10S,11R,15S,18R)-5-acetyl-6,15,18-trihydroxy-12,12-dimethyl-9,17-dioxapentacyclo[8.5.3.01,11.02,7.07,18]octadecan-8-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H28O7
assistant