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 identified by (1S,2S,4R,6S,7S,9S,10S,11R)-9-hydroxy-6-(2-hydroxyacetyl)-7,11-dimethyl-5-oxapentacyclo[8.8.0.02,7.04,6.011,16]octadec-15-en-14-one ?
user
C21H28O5
assistant