You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule (1S,2S,5S,8R,10R,11R,15R,18R)-6,12,12-trimethyl-17-oxapentacyclo[7.6.2.15,8.01,11.02,8]octadec-6-ene-9,10,15,18-tetrol ?
user
C20H30O5
assistant