You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Can you give the molecular formula of the molecule (1R,2R,4R,7S,9S,12R)-4,12-diphenyl-3,5,11,13-tetraoxatricyclo[7.4.0.02,7]tridecane ?
user
C21H22O4
assistant