You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance (1S,2S,6R,7S,9R,13R,17S)-4-hydroxy-15-methoxy-2,6,14,17-tetramethyl-10-oxatetracyclo[7.7.1.02,7.013,17]heptadec-14-ene-3,11,16-trione .
user
C21H28O6
assistant