You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (2S,5S,8R,9S,10S,11R,16S,18S)-9,10,15,18-tetrahydroxy-16-methoxy-12,12-dimethyl-6-methylidene-17-oxapentacyclo[7.6.2.15,8.01,11.02,8]octadecan-7-one .
user
C21H30O7
assistant