You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1R)-1-[(3S,4S)-5,7-dimethoxy-4-(2-phenylethenyl)-3,4-dihydro-1H-isochromen-3-yl]ethane-1,2-diol The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H24O5
assistant